From ad21e4e088bec93e34cb46c180b78d918ee9194b Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Wed, 4 Jan 2023 14:38:01 -1000
Subject: [PATCH 01/25] Start hopping channels with TX/RX of SYNC_CLOCKS

Set the initial clock synchronization at less than a millisecond.  The
separation of the TX and RX transactionComplete interrupts is around 650
- 700 uSec.  By letting the transactionCompleteISR routine call
startChannelTimer, the first expire time of the two timers is within 1
millisecond.

The transmit completion routine for SYNC_CLOCKS and the receive routine
for SYNC_CLOCKS both call hopChannel to change to the next frequency.
This ensures that the two radios start hopping as soon as they are
synchronized.
---
 Firmware/LoRaSerial_Firmware/Begin.ino        | 12 ++-
 .../LoRaSerial_Firmware.ino                   |  2 +
 Firmware/LoRaSerial_Firmware/Radio.ino        | 95 +++++++++----------
 Firmware/LoRaSerial_Firmware/States.ino       | 39 +++++---
 4 files changed, 80 insertions(+), 68 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/Begin.ino b/Firmware/LoRaSerial_Firmware/Begin.ino
index 961d93fc..0cf06f9a 100644
--- a/Firmware/LoRaSerial_Firmware/Begin.ino
+++ b/Firmware/LoRaSerial_Firmware/Begin.ino
@@ -100,13 +100,17 @@ void channelTimerHandler()
   channelTimerStart = millis(); //Record when this ISR happened. Used for calculating clock sync.
   radioCallHistory[RADIO_CALL_channelTimerHandler] = channelTimerStart;
 
-  //Restore the full timer interval
-  channelTimer.setInterval_MS(settings.maxDwellTime, channelTimerHandler);
-  channelTimerMsec = settings.maxDwellTime; //ISR update
-  digitalWrite(pin_hop_timer, channelNumber & 1);
+  //If the last timer was used to sync clocks, restore full timer interval
+  if (reloadChannelTimer == true)
+  {
+    reloadChannelTimer = false;
+    channelTimer.setInterval_MS(settings.maxDwellTime, channelTimerHandler);
+    channelTimerMsec = settings.maxDwellTime; //ISR update
+  }
 
   if (settings.frequencyHop)
   {
+    digitalWrite(pin_hop_timer, ((channelNumber + 1) % settings.numberOfChannels) & 1);
     triggerEvent(TRIGGER_CHANNEL_TIMER_ISR);
     timeToHop = true;
   }
diff --git a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
index be1d3708..3ebadf15 100644
--- a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
+++ b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
@@ -170,6 +170,7 @@ SAMDTimer channelTimer(TIMER_TCC); //Available: TC3, TC4, TC5, TCC, TCC1 or TCC2
 volatile uint16_t channelTimerMsec; //Last value programmed into the channel timer
 volatile unsigned long channelTimerStart = 0; //Tracks how long our timer has been running since last hop
 volatile bool timeToHop = false; //Set by channelTimerHandler to indicate that hopChannel needs to be called
+volatile bool reloadChannelTimer = false; //When set channel timer interval needs to be reloaded with settings.maxDwellTime
 
 uint16_t petTimeout = 0; //A reduced amount of time before WDT triggers. Helps reduce amount of time spent petting.
 unsigned long lastPet = 0; //Remebers time of last WDT pet.
@@ -585,6 +586,7 @@ char platformPrefix[25]; //Used for printing platform specific device name, ie "
 //-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 
 bool clockSyncReceiver; //Receives and processes the clock synchronization
+bool startChannelTimerPending; //When true, call startChannelTimer in transactionCompleteISR
 
 //RX and TX time measurements
 uint32_t rxTimeUsec;
diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index 890e8262..86267ae4 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -702,9 +702,17 @@ void printSX1276Registers()
 void transactionCompleteISR(void)
 {
   transactionCompleteMicros = micros();
-  triggerEvent(TRIGGER_TRANSACTION_COMPLETE);
   radioCallHistory[RADIO_CALL_transactionCompleteISR] = millis();
+  triggerEvent(TRIGGER_TRANSACTION_COMPLETE);
+
+  //Start the channel timer if requested
+  if (startChannelTimerPending)
+  {
+    startChannelTimer(); //transactionCompleteISR, upon TX or RX of SYNC_CLOCKS
+    startChannelTimerPending = false; //transactionCompleteISR, upon TX or RX of SYNC_CLOCKS
+  }
 
+  //Signal the state machine that a receive or transmit has completed
   transactionComplete = true;
 }
 
@@ -729,51 +737,6 @@ void updateHopISR()
   }
 }
 
-//As we complete linkup, different airspeeds exit at different rates
-//We adjust the initial clock setup as needed
-int16_t getLinkupOffset()
-{
-  int linkupOffset = 0;
-
-  switch (settings.airSpeed)
-  {
-    default:
-      break;
-    case (40):
-      linkupOffset = 0;
-      break;
-    case (150):
-      linkupOffset = 0;
-      break;
-    case (400):
-      linkupOffset = 0;
-      break;
-    case (1200):
-      linkupOffset = 0;
-      break;
-    case (2400):
-      linkupOffset = 0;
-      break;
-    case (4800):
-      linkupOffset = 0;
-      break;
-    case (9600):
-      linkupOffset = 0;
-      break;
-    case (19200):
-      linkupOffset = 0;
-      break;
-    case (28800):
-      linkupOffset = 0;
-      break;
-    case (38400):
-      linkupOffset = 0;
-      break;
-  }
-
-  return (settings.maxDwellTime - getReceiveCompletionOffset() - linkupOffset); //Reduce the default window by the offset
-}
-
 //=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 //Table for use in calculating the software CRC-16
 //=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
@@ -2529,10 +2492,10 @@ bool transmitDatagram()
     //Hake sure that the transmitted msToNextHop is in the range 0 - maxDwellTime
     if (timeToHop)
       hopChannel();
-    uint16_t msToNextHop = settings.maxDwellTime - (millis() - channelTimerStart); //TX channel timer value
-    memcpy(header, &msToNextHop, sizeof(msToNextHop));
-    header += sizeof(msToNextHop); //aka CHANNEL_TIMER_BYTES
+    unsigned long currentMillis = millis();
+    uint16_t msToNextHop = channelTimerMsec - (currentMillis - channelTimerStart); //TX channel timer value
 
+    //Validate this value
     if (ENABLE_DEVELOPER && (!clockSyncReceiver))
     {
       if ((msToNextHop < 0) || (msToNextHop > settings.maxDwellTime))
@@ -2540,7 +2503,8 @@ bool transmitDatagram()
         int16_t channelTimer;
         uint8_t * data;
 
-        systemPrintln("TX Frame");
+        systemPrint("TX Frame ");
+        systemPrintln(radioDatagramType[txControl.datagramType]);
         data = outgoingPacket;
         if ((settings.operatingMode == MODE_POINT_TO_POINT) || settings.verifyRxNetID)
         {
@@ -2558,10 +2522,34 @@ bool transmitDatagram()
 
         systemPrint("ERROR: Invalid msToNextHop value, ");
         systemPrintln(msToNextHop);
-        waitForever();
+
+        //Set a valid value
+        msToNextHop = settings.maxDwellTime;
+      }
+      else if (settings.debugSync)
+      {
+        switch (txControl.datagramType)
+        {
+          case DATAGRAM_DATA_ACK:
+          case DATAGRAM_SYNC_CLOCKS:
+            systemPrint("TX: ");
+            systemPrint(channelTimerMsec);
+            systemPrint(" channelTimerMsec + (");
+            systemPrint(currentMillis);
+            systemPrint(" millis() - ");
+            systemPrint(channelTimerStart);
+            systemPrint(" channelTimerStart) = ");
+            systemPrint(msToNextHop);
+            systemPrintln(" mSec");
+          break;
+        }
       }
     } //ENABLE_DEVELOPER
 
+    //Set the time in the frame
+    memcpy(header, &msToNextHop, sizeof(msToNextHop));
+    header += sizeof(msToNextHop); //aka CHANNEL_TIMER_BYTES
+
     if (settings.debugTransmit)
     {
       systemPrintTimestamp();
@@ -2998,6 +2986,7 @@ void startChannelTimer(int16_t startAmount)
   channelTimer.disableTimer();
   channelTimer.setInterval_MS(startAmount, channelTimerHandler);
   digitalWrite(pin_hop_timer, channelNumber & 1);
+  reloadChannelTimer = (startAmount != settings.maxDwellTime);
   timeToHop = false;
   channelTimerStart = millis(); //startChannelTimer - ISR updates value
   channelTimerMsec = startAmount; //startChannelTimer - ISR updates value
@@ -3013,6 +3002,7 @@ void stopChannelTimer()
   //Turn off the channel timer
   channelTimer.disableTimer();
   digitalWrite(pin_hop_timer, channelNumber & 1);
+  channelTimerMsec = 0; //Indicate that the timer is off
 
   triggerEvent(TRIGGER_HOP_TIMER_STOP);
   timeToHop = false;
@@ -3239,6 +3229,9 @@ void syncChannelTimer()
   //Compute the next hop time
   msToNextHop = rmtHopTimeMsec + adjustment;
 
+  //When the ISR fires, reload the channel timer with settings.maxDwellTime
+  reloadChannelTimer = true;
+
   //Restart the channel timer
   channelTimer.setInterval_MS(msToNextHop, channelTimerHandler); //Adjust our hardware timer to match our mate's
   digitalWrite(pin_hop_timer, channelNumber & 1);
diff --git a/Firmware/LoRaSerial_Firmware/States.ino b/Firmware/LoRaSerial_Firmware/States.ino
index 927a7b79..6251c474 100644
--- a/Firmware/LoRaSerial_Firmware/States.ino
+++ b/Firmware/LoRaSerial_Firmware/States.ino
@@ -243,18 +243,23 @@ void updateRadioState()
            | P2P_WAIT_TX_FIND_PARTNER_DONE       |                  = true |   |
            |           |                         |                         |   |
            |           | Tx Complete - - - - - > | Rx FIND_PARTNER         |   |
-           |           |   Start Rx              |   Start HOP Timer       |   |
-           |           |   MAX_PACKET_SIZE       |   clockSyncReceiver     |   |
-           |           V                         |     = false             |   |
+           |           |   Start Rx              |   clockSyncReceiver     |   |
+           |           |   MAX_PACKET_SIZE       |     = false             |   |
+           |           V                         |                         |   |
            `---- P2P_WAIT_SYNC_CLOCKS            |                         |   |
                        |                         | Tx SYNC_CLOCKS          |   |
                        |                         V                         |   |
                        |              P2P_WAIT_TX_SYNC_CLOCKS_DONE         |   |
                        |                         |                         |   |
-        Rx SYNC_CLOCKS | < - - - - - - - - - - - | Tx Complete             |   |
+       Rx Complete ISR | < - - - - - - - - - - - | Tx Complete ISR         |   |
+                       |                         |   Start HOP Timer       |   |
+                       | Start HOP Timer         |                         |   |
+                       |                         V                         |   |
+                       V                         | In state machine        |   |
+        Rx SYNC_CLOCKS | In state machine        | Tx Complete             |   |
                        |                         |   Start Rx              |   |
-                       | Start HOP Timer         |   MAX_PACKET_SIZE       |   |
-                       | Sync HOP Timer          |                         |   |
+                       |                         |   MAX_PACKET_SIZE       |   |
+                       |                         |                         |   |
                        |                         V         Timeout         |   |
                        |                P2P_WAIT_ZERO_ACKS ----------------'   |
                        |                         |                             |
@@ -321,9 +326,6 @@ void updateRadioState()
             //Compute the receive time
             COMPUTE_RX_TIME(rxData, 1);
 
-            //Start the channel timer
-            startChannelTimer(); //Start hopping - P2P clock source
-
             //This system is the source of clock synchronization
             clockSyncReceiver = false; //P2P clock source
 
@@ -338,6 +340,7 @@ void updateRadioState()
             triggerEvent(TRIGGER_TX_SYNC_CLOCKS);
             if (xmitDatagramP2PSyncClocks() == true)
             {
+              startChannelTimerPending = true; //Starts at SYNC_CLOCKS TX done
               sf6ExpectedSize = headerBytes + P2P_ZERO_ACKS_BYTES + trailerBytes; //Tell SF6 we expect ZERO_ACKS to contain millis info
               changeState(RADIO_P2P_WAIT_TX_SYNC_CLOCKS_DONE);
             }
@@ -367,6 +370,7 @@ void updateRadioState()
         COMPUTE_TX_TIME();
         triggerEvent(TRIGGER_TX_DONE);
         transactionComplete = false; //Reset ISR flag
+        startChannelTimerPending = true; //Starts at RX of SYNC_CLOCKS frame
         returnToReceiving();
         changeState(RADIO_P2P_WAIT_SYNC_CLOCKS);
       }
@@ -378,6 +382,13 @@ void updateRadioState()
         //Decode the received packet
         PacketType packetType = rcvDatagram();
 
+        //Restart the channel timer when the SYNC_CLOCKS frame is received
+        if (packetType != DATAGRAM_SYNC_CLOCKS)
+        {
+          stopChannelTimer(); //Restart channel timer if SYNC_CLOCKS not RX
+          startChannelTimerPending = true; //Restart channel timer if SYNC_CLOCKS not RX
+        }
+
         //Process the received datagram
         switch (packetType)
         {
@@ -416,10 +427,6 @@ void updateRadioState()
 
           case DATAGRAM_SYNC_CLOCKS:
             //Received SYNC_CLOCKS
-            //Start the channel timer
-            startChannelTimer(); //Start hopping - P2P clock receiver
-            syncChannelTimer();
-
             //Display the channelTimer sink
             if (settings.debugSync)
             {
@@ -430,6 +437,9 @@ void updateRadioState()
             //Compute the receive time
             COMPUTE_RX_TIME(rxData + 1, 1);
 
+            //Hop to the next channel
+            hopChannel();
+
             //Acknowledge the SYNC_CLOCKS
             triggerEvent(TRIGGER_TX_ZERO_ACKS);
             if (xmitDatagramP2PZeroAcks() == true)
@@ -477,6 +487,9 @@ void updateRadioState()
         COMPUTE_TX_TIME();
         triggerEvent(TRIGGER_TX_DONE);
         transactionComplete = false; //Reset ISR flag
+
+        //Hop to the next channel
+        hopChannel();
         returnToReceiving();
         changeState(RADIO_P2P_WAIT_ZERO_ACKS);
       }

From ab5b53774f0fa4474f519c8390d9d0e3323fedf4 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Wed, 4 Jan 2023 14:42:56 -1000
Subject: [PATCH 02/25] Compute the retransmit timeout (backoff) in
 retransmitDatagram

---
 Firmware/LoRaSerial_Firmware/Radio.ino  |   6 +-
 Firmware/LoRaSerial_Firmware/States.ino | 106 ++++++++++++------------
 2 files changed, 57 insertions(+), 55 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index 86267ae4..e11f40a2 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -2961,7 +2961,11 @@ bool retransmitDatagram(VIRTUAL_CIRCUIT * vc)
 
   frameAirTime += responseDelay;
   datagramTimer = millis(); //Move timestamp even if error
-  retransmitTimeout = random(ackAirTime, frameAirTime + ackAirTime); //Wait this number of ms between retransmits. Increases with each re-transmit.
+
+  //Compute the interval before a retransmission occurs in milliseconds,
+  //this value increases with each transmission
+  retransmitTimeout = random(ackAirTime, frameAirTime + ackAirTime)
+                    * (frameSentCount + 1) * 3 / 2;
 
   //BLink the RX LED
   if (settings.selectLedUse == LEDS_RADIO_USE)
diff --git a/Firmware/LoRaSerial_Firmware/States.ino b/Firmware/LoRaSerial_Firmware/States.ino
index 6251c474..88f6d8c8 100644
--- a/Firmware/LoRaSerial_Firmware/States.ino
+++ b/Firmware/LoRaSerial_Firmware/States.ino
@@ -836,73 +836,71 @@ void updateRadioState()
         //An ACK is expected when the ACK timer running
         else if (ackTimer)
         {
-          //Check for ACK timeout
-          if ((millis() - ackTimer) >= (frameAirTime + ackAirTime + settings.overheadTime + getReceiveCompletionOffset()))
+          //Throttle back retransmits based on the number of retransmits we've attempted
+          //retransmitTimeout is a random number set in retransmitDatagram
+          if (millis() - datagramTimer > retransmitTimeout)
           {
             //Determine if another retransmission is allowed
             if ((!settings.maxResends) || (frameSentCount < settings.maxResends))
             {
-              //Throttle back retransmits based on the number of retransmits we've attempted
-              //retransmitTimeout is a random number, set when the first datagram is sent
-              if (millis() - datagramTimer > (frameSentCount * retransmitTimeout))
+              lostFrames++;
+
+              //Display the retransmit
+              if (settings.debugDatagrams)
               {
-                lostFrames++;
+                systemPrintTimestamp();
+                systemPrintln("RX: ACK Timeout");
+                outputSerialData(true);
+              }
 
-                //Display the retransmit
-                if (settings.debugDatagrams)
+              if (settings.debugDatagrams)
+              {
+                systemPrintTimestamp();
+                systemPrint("TX: Retransmit ");
+                systemPrint(frameSentCount);
+                systemPrint(", ");
+                systemPrint(radioDatagramType[txControl.datagramType]);
+                switch (txControl.datagramType)
                 {
-                  systemPrintTimestamp();
-                  systemPrintln("RX: ACK Timeout");
-                  outputSerialData(true);
-                }
+                  default:
+                    systemPrintln();
+                    break;
 
-                triggerEvent(TRIGGER_RETRANSMIT);
-                if (settings.debugDatagrams)
-                {
-                  systemPrintTimestamp();
-                  systemPrint("TX: Retransmit ");
-                  systemPrint(frameSentCount);
-                  systemPrint(", ");
-                  systemPrint(radioDatagramType[txControl.datagramType]);
-                  switch (txControl.datagramType)
-                  {
-                    default:
-                      systemPrintln();
-                      break;
-
-                    case DATAGRAM_DATA:
-                    case DATAGRAM_DATA_ACK:
-                    case DATAGRAM_REMOTE_COMMAND:
-                    case DATAGRAM_REMOTE_COMMAND_RESPONSE:
-                    case DATAGRAM_HEARTBEAT:
-                      systemPrint(" (ACK #");
-                      systemPrint(txControl.ackNumber);
-                      systemPrint(")");
-                      systemPrintln();
-                      break;
-                  }
-                  outputSerialData(true);
+                  case DATAGRAM_DATA:
+                  case DATAGRAM_DATA_ACK:
+                  case DATAGRAM_REMOTE_COMMAND:
+                  case DATAGRAM_REMOTE_COMMAND_RESPONSE:
+                  case DATAGRAM_HEARTBEAT:
+                    systemPrint(" (ACK #");
+                    systemPrint(txControl.ackNumber);
+                    systemPrint(")");
+                    systemPrintln();
+                    break;
                 }
+                outputSerialData(true);
+              }
 
-                //Attempt the retransmission
-                RESTORE_TX_BUFFER();
-                if (rexmtControl.datagramType == DATAGRAM_HEARTBEAT)
+              //Attempt the retransmission
+              RESTORE_TX_BUFFER();
+              if (rexmtControl.datagramType == DATAGRAM_HEARTBEAT)
+              {
+                //Never retransmit the heartbeat, always send a new version to
+                //send the updated time value
+                if (xmitDatagramP2PHeartbeat() == true)
                 {
-                  //Never retransmit the heartbeat, always send a new version to
-                  //send the updated time value
-                  if (xmitDatagramP2PHeartbeat() == true)
-                  {
-                    changeState(RADIO_P2P_LINK_UP_WAIT_TX_DONE);
-                    triggerEvent(TRIGGER_TX_HEARTBEAT);
-                  }
-                }
-                else if (retransmitDatagram(NULL) == true)
+                  triggerEvent(TRIGGER_TX_HEARTBEAT);
                   changeState(RADIO_P2P_LINK_UP_WAIT_TX_DONE);
-
-                //We're re-sending data, so don't be the first to send next heartbeat
-                setHeartbeatLong();
-                START_ACK_TIMER();
+                }
               }
+              else if (retransmitDatagram(NULL) == true)
+              {
+                triggerEvent(TRIGGER_RETRANSMIT);
+                changeState(RADIO_P2P_LINK_UP_WAIT_TX_DONE);
+              }
+
+              //We're re-sending data, so don't be the first to send next heartbeat
+              setHeartbeatLong();
+              START_ACK_TIMER();
             }
             else
             {

From 798d3096cde48e319d37647df03b9366890266c1 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Fri, 6 Jan 2023 12:57:51 -1000
Subject: [PATCH 03/25] Clear timeToHop when delaying the hop

---
 Firmware/LoRaSerial_Firmware/Radio.ino | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index e11f40a2..0cd3df6b 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -3076,6 +3076,7 @@ void syncChannelTimer()
   //the channelTimerStart value indicated that it was done.  The channel
   //timer update will add only microseconds to when the hop is done.
   delayedHopCount = timeToHop ? 1 : 0;
+  timeToHop = false;
 
   //The radios are using the same frequencies since the frame was successfully
   //received.  The goal is to adjust the channel timer to fire in close proximity

From ab58f447fd0be3a5c2453a84af002d8936c61a99 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Fri, 6 Jan 2023 12:59:12 -1000
Subject: [PATCH 04/25] Don't spin forever when a channel timer value error is
 detected on RX

---
 Firmware/LoRaSerial_Firmware/Radio.ino | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index 0cd3df6b..6c1eefc7 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -3059,7 +3059,7 @@ void syncChannelTimer()
 
       systemPrint("ERROR: Invalid msToNextHopRemote value, ");
       systemPrintln(msToNextHopRemote);
-      waitForever();
+      return;
     }
   } //ENABLE_DEVELOPER
 

From e9519a760767ce60f01c1de24a62823973348fc7 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Fri, 6 Jan 2023 13:18:07 -1000
Subject: [PATCH 05/25] Fix the case when both the remote and local values are
 negative

---
 Firmware/LoRaSerial_Firmware/Radio.ino | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index 6c1eefc7..f3a59320 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -3105,8 +3105,7 @@ void syncChannelTimer()
   adjustment = 0;
 
 #define REMOTE_SYSTEM_LIKELY_TO_HOP_MSEC    2
-#define CHANNEL_TIMER_SYNC_PLUS_MINUS_MSEC  3
-#define CHANNEL_TIMER_SYNC_MSEC             (2 * CHANNEL_TIMER_SYNC_PLUS_MINUS_MSEC)
+#define CHANNEL_TIMER_SYNC_MSEC   (txRxTimeMsec + REMOTE_SYSTEM_LIKELY_TO_HOP_MSEC)
 
   //Determine if the remote has hopped or is likely to hop very soon
   if (rmtHopTimeMsec <= REMOTE_SYSTEM_LIKELY_TO_HOP_MSEC)
@@ -3115,7 +3114,7 @@ void syncChannelTimer()
     adjustment += settings.maxDwellTime;
 
     //Determine if the local system has just hopped
-    if (lclHopTimeMsec <= CHANNEL_TIMER_SYNC_MSEC)
+    if (((unsigned long)lclHopTimeMsec) <= CHANNEL_TIMER_SYNC_MSEC)
     {
       //Case 1 above, both systems using the same channel
       //
@@ -3176,7 +3175,7 @@ void syncChannelTimer()
   {
     //The remote system has not hopped
     //Determine if the local system has just hopped
-    if (lclHopTimeMsec <= CHANNEL_TIMER_SYNC_MSEC)
+    if (((unsigned long)lclHopTimeMsec) <= CHANNEL_TIMER_SYNC_MSEC)
     {
       //Case 3 above, extend the channel timer value
       //

From fc83ce5e3503004905a60d3f5d71af08d1ecc74b Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Sat, 7 Jan 2023 12:34:07 -1000
Subject: [PATCH 06/25] Transmit a valid value of channelTimer when the timer
 is not running

---
 Firmware/LoRaSerial_Firmware/Radio.ino | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index f3a59320..a9595f23 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -2493,7 +2493,11 @@ bool transmitDatagram()
     if (timeToHop)
       hopChannel();
     unsigned long currentMillis = millis();
-    uint16_t msToNextHop = channelTimerMsec - (currentMillis - channelTimerStart); //TX channel timer value
+    uint16_t msToNextHop; //TX channel timer value
+    if (channelTimerMsec)
+      msToNextHop = channelTimerMsec - (currentMillis - channelTimerStart);
+    else
+      msToNextHop = settings.maxDwellTime;
 
     //Validate this value
     if (ENABLE_DEVELOPER && (!clockSyncReceiver))

From 6542a09ea32d356dd992dc677e70dc67a736d241 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Sat, 7 Jan 2023 12:34:55 -1000
Subject: [PATCH 07/25] Stop the channel timer when the P2P link is down

---
 Firmware/LoRaSerial_Firmware/States.ino | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Firmware/LoRaSerial_Firmware/States.ino b/Firmware/LoRaSerial_Firmware/States.ino
index 88f6d8c8..b9ce991b 100644
--- a/Firmware/LoRaSerial_Firmware/States.ino
+++ b/Firmware/LoRaSerial_Firmware/States.ino
@@ -293,6 +293,10 @@ void updateRadioState()
         setRadioFrequency(false);
       }
 
+      //Stop the channel timer if it is running
+      if (channelTimerMsec)
+        stopChannelTimer();
+
       //Determine if a FIND_PARTNER was received
       if (transactionComplete)
       {

From 2be3dabe2409fbcb812546fdf813c9bcc45c27a2 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Sat, 7 Jan 2023 12:49:52 -1000
Subject: [PATCH 08/25] Better handle the LEDs

Perform the LED operations conditionally depending upon the state of
settings.selectLedUse.  This commit:

* Adds a routine to blink the RSSI LED or LEDs
* Renames the routine to blink the serial TX LED
* Renames the routine to blink the serial RX LED
* Adds a routine to blink the radio RX LED
* Adds a routine to blink the radio TX LED
* Adds a routine to blink the heartbeat LED
* Adds a routine to blink the hop LED
---
 .../LoRaSerial_Firmware.ino                   |  23 +-
 Firmware/LoRaSerial_Firmware/Radio.ino        |  13 +-
 Firmware/LoRaSerial_Firmware/Serial.ino       |   8 +-
 Firmware/LoRaSerial_Firmware/States.ino       |   7 +-
 Firmware/LoRaSerial_Firmware/System.ino       | 301 ++++++++++++------
 5 files changed, 214 insertions(+), 138 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
index 3ebadf15..62a31a3b 100644
--- a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
+++ b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
@@ -125,14 +125,16 @@ uint8_t pin_hop_timer = PIN_UNDEFINED;
 #define RADIO_USE_BAD_FRAMES_LED  BLUE_LED    //Blue
 #define RADIO_USE_BAD_CRC_LED     YELLOW_LED  //Yellow
 
-#define LED_MP_HOP_CHANNEL        BLUE_LED
-#define LED_MP_HEARTBEAT          YELLOW_LED
+#define LED_MP_HEARTBEAT          BLUE_LED
+#define LED_MP_HOP_CHANNEL        YELLOW_LED
 
 #define CYLON_TX_DATA_LED   BLUE_LED
 #define CYLON_RX_DATA_LED   YELLOW_LED
 
 #define LED_ON              HIGH
 #define LED_OFF             LOW
+
+#define LED_MAX_PULSE_WIDTH     24 //mSec
 //-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 
 //Radio Library
@@ -364,10 +366,8 @@ bool writeOnCommandExit = false; //Goes true if user specifies ATW command
 
 //Global variables - LEDs
 //-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
-int trainCylonNumber = 0b0001;
-int trainCylonDirection = -1;
-
-unsigned long lastTrainBlink = 0; //Controls LED during training
+uint8_t cylonLedPattern = 0b0001;
+bool cylonPatternGoingLeft;
 //-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 
 //Global variables - Radio (General)
@@ -390,19 +390,8 @@ float frequencyCorrection = 0; //Adjust receive freq based on the last packet re
 
 volatile bool hop = true; //Clear the DIO1 hop ISR when possible
 
-//RSSI must be above these negative numbers for LED to illuminate
-const int rssiLevelLow = -150;
-const int rssiLevelMed = -120;
-const int rssiLevelHigh = -100;
-const int rssiLevelMax = -70;
 int rssi; //Average signal level, measured during reception of a packet
 
-//LED control values
-uint32_t ledPreviousRssiMillis;
-uint32_t ledHeartbeatMillis;
-int8_t ledRssiCount; //Pulse width count for LED display
-int8_t ledRssiValue; //Target pulse width count for LED display
-
 //Link quality metrics
 uint32_t datagramsSent;     //Total number of datagrams sent
 uint32_t datagramsReceived; //Total number of datagrams received
diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index a9595f23..fe1929a1 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -558,6 +558,7 @@ void hopChannel(bool moveForwardThroughTable, uint8_t channelCount)
 
   //Select the new frequency
   setRadioFrequency(radioStateTable[radioState].rxState);
+  blinkChannelHopLed(true);
 }
 
 //Determine the time in milliseconds when channel zero is reached again
@@ -2190,10 +2191,7 @@ PacketType rcvDatagram()
   linkDownTimer = millis();
 
   //Blink the RX LED
-  if (settings.selectLedUse == LEDS_RADIO_USE)
-    digitalWrite(RADIO_USE_RX_DATA_LED, LED_ON);
-  else if (settings.selectLedUse == LEDS_CYLON)
-    digitalWrite(CYLON_RX_DATA_LED, LED_ON);
+  blinkRadioRxLed(true);
   return datagramType;
 }
 
@@ -2971,11 +2969,8 @@ bool retransmitDatagram(VIRTUAL_CIRCUIT * vc)
   retransmitTimeout = random(ackAirTime, frameAirTime + ackAirTime)
                     * (frameSentCount + 1) * 3 / 2;
 
-  //BLink the RX LED
-  if (settings.selectLedUse == LEDS_RADIO_USE)
-    digitalWrite(RADIO_USE_TX_DATA_LED, LED_ON);
-  else if (settings.selectLedUse == LEDS_CYLON)
-    digitalWrite(CYLON_TX_DATA_LED, LED_ON);
+  //BLink the TX LED
+  blinkRadioTxLed(true);
 
   return (true); //Transmission has started
 }
diff --git a/Firmware/LoRaSerial_Firmware/Serial.ino b/Firmware/LoRaSerial_Firmware/Serial.ino
index dc31408e..7a13f2d4 100644
--- a/Firmware/LoRaSerial_Firmware/Serial.ino
+++ b/Firmware/LoRaSerial_Firmware/Serial.ino
@@ -247,7 +247,7 @@ void updateSerial()
   previousHead = rxHead;
   while (rtsAsserted && arch.serialAvailable() && (transactionComplete == false))
   {
-    rxLED(true); //Turn on LED during serial reception
+    blinkSerialRxLed(true); //Turn on LED during serial reception
 
     //Take a break if there are ISRs to attend to
     petWDT();
@@ -262,7 +262,7 @@ void updateSerial()
     serialReceiveBuffer[rxHead++] = incoming; //Push char to holding buffer
     rxHead %= sizeof(serialReceiveBuffer);
   } //End Serial.available()
-  rxLED(false); //Turn off LED
+  blinkSerialRxLed(false); //Turn off LED
 
   //Print the number of bytes received via serial
   if (settings.debugSerial && (rxHead - previousHead))
@@ -440,7 +440,7 @@ void outputSerialData(bool ignoreISR)
   dataBytes = availableTXBytes();
   while (dataBytes-- && isCTS() && (ignoreISR || (!transactionComplete)))
   {
-    txLED(true); //Turn on LED during serial transmissions
+    blinkSerialTxLed(true); //Turn on LED during serial transmissions
 
     //Take a break if there are ISRs to attend to
     petWDT();
@@ -452,7 +452,7 @@ void outputSerialData(bool ignoreISR)
     txTail++;
     txTail %= sizeof(serialTransmitBuffer);
   }
-  txLED(false); //Turn off LED
+  blinkSerialTxLed(false); //Turn off LED
 }
 
 //=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
diff --git a/Firmware/LoRaSerial_Firmware/States.ino b/Firmware/LoRaSerial_Firmware/States.ino
index b9ce991b..057add9b 100644
--- a/Firmware/LoRaSerial_Firmware/States.ino
+++ b/Firmware/LoRaSerial_Firmware/States.ino
@@ -741,6 +741,7 @@ void updateRadioState()
             //Adjust the timestamp offset
             COMPUTE_TIMESTAMP_OFFSET(rxData, 1);
             triggerEvent(TRIGGER_RX_HEARTBEAT);
+            blinkHeartbeatLed(true);
 
             //Transmit ACK
             P2P_SEND_ACK(TRIGGER_TX_ACK);
@@ -1288,7 +1289,7 @@ void updateRadioState()
 
             lastPacketReceived = millis(); //Update timestamp for Link LED
 
-            ledMpHeartbeatOn();
+            blinkHeartbeatLed(true);
             changeState(RADIO_MP_STANDBY);
             break;
 
@@ -1330,7 +1331,6 @@ void updateRadioState()
               setHeartbeatMultipoint(); //We're sending something with clock data so reset heartbeat timer
               changeState(RADIO_MP_WAIT_TX_DONE); //Wait for heartbeat to transmit
             }
-            ledMpHeartbeatOn();
           }
         }
 
@@ -2903,6 +2903,9 @@ void vcReceiveHeartbeat(uint32_t rxMillis)
   //Update the timestamp offset
   if (rxSrcVc == VC_SERVER)
   {
+    //Blink the heartbeat LED
+    blinkHeartbeatLed(true);
+
     //Assume client and server are running the same level of debugging,
     //then the delay from reading the millisecond value on the server should
     //get offset by the transmit setup time and the receive overhead time.
diff --git a/Firmware/LoRaSerial_Firmware/System.ino b/Firmware/LoRaSerial_Firmware/System.ino
index 0d17a326..9e2de995 100644
--- a/Firmware/LoRaSerial_Firmware/System.ino
+++ b/Firmware/LoRaSerial_Firmware/System.ino
@@ -592,31 +592,166 @@ void setRSSI(uint8_t ledBits)
     digitalWrite(pin_rssi4LED, LOW);
 }
 
+//Start the cylon LEDs
+void startCylonLEDs()
+{
+  cylonLedPattern = 0b0001;
+  cylonPatternGoingLeft = true;
+}
+
+//Update the RSSI LED or LEDs
+void blinkRadioRssiLed()
+{
+  unsigned long currentMillis;
+  static uint32_t ledPreviousRssiMillis;
+  static unsigned long lastCylonBlink; //Controls LED during training
+  static int8_t ledRssiPulseWidth; //Target pulse width for LED display
+
+  currentMillis = millis();
+  switch (settings.selectLedUse)
+  {
+    //Update the pattern on the 4 green LEDs
+    case LEDS_CYLON:
+      //Determine if it is time to update the cylon pattern
+      if ((currentMillis - lastCylonBlink) > 75)
+      {
+        lastCylonBlink = currentMillis;
+
+	//The following shows the cylon pattern in four LEDs
+	//
+	//	LED3  LED2  LED1  LED0
+	//                         X
+	//		      X
+	//		X
+	//	  X
+	//		X
+	//		      X
+	//                         X
+	//		      X
+	//		...
+	//
+        //Cylon the RSSI LEDs
+        setRSSI(cylonLedPattern);
+
+	//Determine if a change in direction is necessary
+        if ((cylonLedPattern == 0b1000) || (cylonLedPattern == 0b0001))
+          cylonPatternGoingLeft = cylonPatternGoingLeft ? false : true;
+
+        if (cylonPatternGoingLeft)
+          cylonLedPattern <<= 1;
+        else
+          cylonLedPattern >>= 1;
+      }
+      break;
+
+    //Update the single RSSI LED
+    case LEDS_MULTIPOINT:
+    case LEDS_RADIO_USE:
+      //Check for the start of a new pulse
+      if ((currentMillis - ledPreviousRssiMillis) >= LED_MAX_PULSE_WIDTH)
+      {
+        ledPreviousRssiMillis = currentMillis;
+
+        //Determine the RSSI LED pulse width
+        //The RSSI value ranges from -164 to 30 dB
+        ledRssiPulseWidth = (150 + rssi) / 10;
+        if (ledRssiPulseWidth > 0)
+          digitalWrite(RADIO_USE_RSSI_LED, LED_ON);
+      }
+
+      //Check for time to turn off the LED
+      else if ((currentMillis - ledPreviousRssiMillis) >= ledRssiPulseWidth)
+        digitalWrite(RADIO_USE_RSSI_LED, LED_OFF);
+      break;
+
+    //Update the 4 green LEDs based upon the RSSI value
+    case LEDS_RSSI:
+      if (rssi > -70)
+        setRSSI(0b1111);
+      else if (rssi > -100)
+        setRSSI(0b0111);
+      else if (rssi > -120)
+        setRSSI(0b0011);
+      else if (rssi > -150)
+        setRSSI(0b0001);
+      else
+        setRSSI(0);
+      break;
+  }
+}
+
 //Set the serial TX (blue) LED value
-void txLED(bool illuminate)
+void blinkSerialTxLed(bool illuminate)
 {
-  if (settings.selectLedUse != LEDS_RSSI)
-    return;
-  if (pin_txLED != PIN_UNDEFINED)
+  switch (settings.selectLedUse)
   {
-    if (illuminate == true)
-      digitalWrite(pin_txLED, HIGH);
-    else
-      digitalWrite(pin_txLED, LOW);
+    case LEDS_RSSI:
+      if (pin_txLED != PIN_UNDEFINED)
+      {
+        if (illuminate == true)
+          digitalWrite(pin_txLED, HIGH);
+        else
+          digitalWrite(pin_txLED, LOW);
+      }
+      break;
   }
 }
 
 //Set the serial RX (yellow) LED value
-void rxLED(bool illuminate)
+void blinkSerialRxLed(bool illuminate)
 {
-  if (settings.selectLedUse != LEDS_RSSI)
-    return;
-  if (pin_rxLED != PIN_UNDEFINED)
+  switch (settings.selectLedUse)
+  {
+    case LEDS_RSSI:
+      if (illuminate == true)
+        digitalWrite(pin_rxLED, HIGH);
+      else
+        digitalWrite(pin_rxLED, LOW);
+    break;
+  }
+}
+
+//Blink the RX LED
+void blinkRadioRxLed(bool on)
+{
+  switch (settings.selectLedUse)
+  {
+    case LEDS_CYLON:
+      if (on)
+        digitalWrite(CYLON_RX_DATA_LED, LED_ON);
+      else if ((millis() - linkDownTimer) >= RADIO_USE_BLINK_MILLIS)
+        digitalWrite(CYLON_RX_DATA_LED, LED_OFF);
+      break;
+
+    case LEDS_MULTIPOINT:
+    case LEDS_RADIO_USE:
+      if (on)
+        digitalWrite(RADIO_USE_RX_DATA_LED, LED_ON);
+      else if ((millis() - linkDownTimer) >= RADIO_USE_BLINK_MILLIS)
+        digitalWrite(RADIO_USE_RX_DATA_LED, LED_OFF);
+      break;
+  }
+}
+
+//BLink the TX LED
+void blinkRadioTxLed(bool on)
+{
+  switch (settings.selectLedUse)
   {
-    if (illuminate == true)
-      digitalWrite(pin_rxLED, HIGH);
-    else
-      digitalWrite(pin_rxLED, LOW);
+    case LEDS_CYLON:
+      if (on)
+        digitalWrite(CYLON_TX_DATA_LED, LED_ON);
+      else if ((millis() - datagramTimer) >= RADIO_USE_BLINK_MILLIS)
+        digitalWrite(CYLON_TX_DATA_LED, LED_OFF);
+      break;
+
+    case LEDS_MULTIPOINT:
+    case LEDS_RADIO_USE:
+      if (on)
+        digitalWrite(RADIO_USE_TX_DATA_LED, LED_ON);
+      else if ((millis() - datagramTimer) >= RADIO_USE_BLINK_MILLIS)
+        digitalWrite(RADIO_USE_TX_DATA_LED, LED_OFF);
+      break;
   }
 }
 
@@ -636,16 +771,19 @@ void radioLeds()
   static uint32_t badCrcMillis;
 
   //Turn off the RX LED to end the blink
-  currentMillis = millis();
-  if ((currentMillis - linkDownTimer) >= RADIO_USE_BLINK_MILLIS)
-    digitalWrite(RADIO_USE_RX_DATA_LED, LED_OFF);
+  blinkRadioRxLed(false);
 
   //Turn off the TX LED to end the blink
-  currentMillis = millis();
-  if ((currentMillis - datagramTimer) >= RADIO_USE_BLINK_MILLIS)
-    digitalWrite(RADIO_USE_TX_DATA_LED, LED_OFF);
+  blinkRadioTxLed(false);
+
+  //Update the link LED
+  digitalWrite(RADIO_USE_LINK_LED, isLinked() ? LED_ON : LED_OFF);
+
+  //Update the RSSI LED
+  blinkRadioRssiLed();
 
   //Blink the bad frames LED
+  currentMillis = millis();
   if (badFrames != previousBadFrames)
   {
     previousBadFrames = badFrames;
@@ -676,35 +814,39 @@ void radioLeds()
     badCrcMillis = 0;
     digitalWrite(RADIO_USE_BAD_CRC_LED, LED_OFF);
   }
+}
 
-  //Update the link LED
-  digitalWrite(RADIO_USE_LINK_LED, isLinked() ? LED_ON : LED_OFF);
+//Blink the heartbeat LED
+void blinkHeartbeatLed(bool on)
+{
+  static unsigned long ledHeartbeatMillis;
 
-  //Update the RSSI LED
-  if (currentMillis != ledPreviousRssiMillis)
+  switch (settings.selectLedUse)
   {
-    if (ledRssiCount >= 16)
-    {
-      ledRssiValue = (150 + rssi) / 10;
-      ledRssiCount = 0;
-      if (ledRssiValue >= ledRssiCount)
-        digitalWrite(RADIO_USE_RSSI_LED, LED_ON);
-    }
-
-    //Turn off the RSSI LED
-    else if (ledRssiValue < ledRssiCount++)
-      digitalWrite(RADIO_USE_RSSI_LED, LED_OFF);
+    case LEDS_MULTIPOINT:
+      if (on)
+      {
+        digitalWrite(LED_MP_HEARTBEAT, LED_ON);
+        ledHeartbeatMillis = millis();
+      }
+      else if ((millis() - ledHeartbeatMillis) > RADIO_USE_BLINK_MILLIS)
+        digitalWrite(LED_MP_HEARTBEAT, LED_OFF);
+      break;
   }
-
-  //Save the last millis value
-  ledPreviousRssiMillis = currentMillis;
 }
 
-//Turn on the heartbeat LED
-void ledMpHeartbeatOn()
+//Blink the channel hop LED
+void blinkChannelHopLed(bool on)
 {
-  digitalWrite(LED_MP_HEARTBEAT, LED_OFF);
-  ledHeartbeatMillis = millis();
+  switch (settings.selectLedUse)
+  {
+    case LEDS_MULTIPOINT:
+      if (on)
+        digitalWrite(LED_MP_HOP_CHANNEL, LED_ON);
+      else if ((millis() - radioCallHistory[RADIO_CALL_hopChannel]) >= RADIO_USE_BLINK_MILLIS)
+        digitalWrite(LED_MP_HOP_CHANNEL, LED_OFF);
+      break;
+  }
 }
 
 //Display the multi-point LED pattern
@@ -713,83 +855,37 @@ void multiPointLeds()
   uint32_t currentMillis;
 
   //Turn off the RX LED to end the blink
-  currentMillis = millis();
-  if ((currentMillis - linkDownTimer) >= RADIO_USE_BLINK_MILLIS)
-    digitalWrite(RADIO_USE_RX_DATA_LED, LED_OFF);
+  blinkRadioRxLed(false);
 
   //Turn off the TX LED to end the blink
-  currentMillis = millis();
-  if ((currentMillis - datagramTimer) >= RADIO_USE_BLINK_MILLIS)
-    digitalWrite(RADIO_USE_TX_DATA_LED, LED_OFF);
+  blinkRadioTxLed(false);
 
   //Update the sync LED
   digitalWrite(RADIO_USE_LINK_LED, isMultiPointSync() ? LED_ON : LED_OFF);
 
   //Update the RSSI LED
-  if (currentMillis != ledPreviousRssiMillis)
-  {
-    if (ledRssiCount >= 16)
-    {
-      ledRssiValue = (150 + rssi) / 10;
-      ledRssiCount = 0;
-      if (ledRssiValue >= ledRssiCount)
-        digitalWrite(RADIO_USE_RSSI_LED, LED_ON);
-    }
-
-    //Turn off the RSSI LED
-    else if (ledRssiValue < ledRssiCount++)
-      digitalWrite(RADIO_USE_RSSI_LED, LED_OFF);
-  }
+  blinkRadioRssiLed();
 
   //Update the hop LED
   if ((millis() - radioCallHistory[RADIO_CALL_hopChannel]) >= RADIO_USE_BLINK_MILLIS)
     digitalWrite(LED_MP_HOP_CHANNEL, LED_OFF);
 
   //Update the HEARTBEAT LED
-  if ((millis() - ledHeartbeatMillis) >= RADIO_USE_BLINK_MILLIS)
-    digitalWrite(LED_MP_HEARTBEAT, LED_OFF);
-
-  //Save the last millis value
-  ledPreviousRssiMillis = currentMillis;
-}
-
-//Start the cylon LEDs
-void startCylonLEDs()
-{
-  trainCylonNumber = 0b0001;
-  trainCylonDirection = -1;
+  blinkHeartbeatLed(false);
 }
 
 //Update the cylon LEDs
 void updateCylonLEDs()
 {
-  unsigned long currentMillis;
-
-  currentMillis = millis();
-  if ((currentMillis - lastTrainBlink) > 75) //Blink while unit waits in training state
-  {
-    lastTrainBlink = millis();
-
-    //Cylon the RSSI LEDs
-    setRSSI(trainCylonNumber);
-
-    if (trainCylonNumber == 0b1000 || trainCylonNumber == 0b0001)
-      trainCylonDirection *= -1; //Change direction
-
-    if (trainCylonDirection > 0)
-      trainCylonNumber <<= 1;
-    else
-      trainCylonNumber >>= 1;
-  }
+  //Display the cylon pattern on the RSSI LEDs
+  blinkRadioRssiLed();
 
   //Use the blue and yellow LEDS to indicate radio activity during training
   //Turn off the RX LED to end the blink
-  if ((currentMillis - linkDownTimer) >= RADIO_USE_BLINK_MILLIS)
-    digitalWrite(CYLON_RX_DATA_LED, LED_OFF);
+  blinkRadioRxLed(false);
 
   //Turn off the TX LED to end the blink
-  if ((currentMillis - datagramTimer) >= RADIO_USE_BLINK_MILLIS)
-    digitalWrite(CYLON_TX_DATA_LED, LED_OFF);
+  blinkRadioTxLed(false);
 }
 
 //Update the LED values depending upon the selected display
@@ -816,14 +912,7 @@ void updateLeds()
     //Set LEDs according to RSSI level
     default:
     case LEDS_RSSI:
-      if (rssi > rssiLevelLow)
-        setRSSI(0b0001);
-      if (rssi > rssiLevelMed)
-        setRSSI(0b0011);
-      if (rssi > rssiLevelHigh)
-        setRSSI(0b0111);
-      if (rssi > rssiLevelMax)
-        setRSSI(0b1111);
+      blinkRadioRssiLed();
       break;
 
     case LEDS_RADIO_USE:

From 91aca0aadfb3c38f66fad1929c18544541f6e13e Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Sun, 8 Jan 2023 14:17:49 -1000
Subject: [PATCH 09/25] Add the timestamp to link up and link down display

---
 Firmware/LoRaSerial_Firmware/States.ino | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/Firmware/LoRaSerial_Firmware/States.ino b/Firmware/LoRaSerial_Firmware/States.ino
index 057add9b..3d3e72f6 100644
--- a/Firmware/LoRaSerial_Firmware/States.ino
+++ b/Firmware/LoRaSerial_Firmware/States.ino
@@ -2618,10 +2618,25 @@ void displayRadioStateHistory()
 //Break a point-to-point link
 void breakLink()
 {
+  unsigned long linkDownTime;
+
   //Break the link
+  if (settings.printTimestamp)
+  {
+    linkDownTime = millis();
+
+    //Offset the value for display
+    if (!settings.displayRealMillis)
+      linkDownTime += timestampOffset;
+  }
   linkFailures++;
   if (settings.printLinkUpDown)
   {
+    if (settings.printTimestamp)
+    {
+      systemPrintTimestamp(linkDownTime);
+      systemPrint(": ");
+    }
     systemPrintln("--------- Link DOWN ---------");
     outputSerialData(true);
   }
@@ -2663,6 +2678,7 @@ void enterLinkUp()
   changeState(RADIO_P2P_LINK_UP);
   if (settings.printLinkUpDown)
   {
+    systemPrintTimestamp();
     systemPrintln("========== Link UP ==========");
     outputSerialData(true);
   }

From 3f2898dc034e0bf92d429635d05ac8c5aba07e28 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Sun, 8 Jan 2023 14:28:23 -1000
Subject: [PATCH 10/25] Add frameAirTimeMsec parameter to syncChannelTime

---
 Firmware/LoRaSerial_Firmware/Radio.ino  |  8 ++++----
 Firmware/LoRaSerial_Firmware/States.ino | 10 +++++-----
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index fe1929a1..9d7d4dcb 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -3013,7 +3013,7 @@ void stopChannelTimer()
 
 //Given the remote unit's number of ms before its next hop,
 //adjust our own channelTimer interrupt to be synchronized with the remote unit
-void syncChannelTimer()
+void syncChannelTimer(uint16_t frameAirTimeMsec)
 {
   int16_t adjustment;
   unsigned long currentMillis;
@@ -3097,14 +3097,14 @@ void syncChannelTimer()
   //Compute the remote system's channel timer firing time offset in milliseconds
   //using the channel timer value and the adjustments for transmit and receive
   //time (time of flight)
-  rmtHopTimeMsec = msToNextHopRemote - txRxTimeMsec;
+  rmtHopTimeMsec = msToNextHopRemote - frameAirTimeMsec;
 
   //Compute the when the local system last hopped
   lclHopTimeMsec = currentMillis - channelTimerStart;
   adjustment = 0;
 
 #define REMOTE_SYSTEM_LIKELY_TO_HOP_MSEC    2
-#define CHANNEL_TIMER_SYNC_MSEC   (txRxTimeMsec + REMOTE_SYSTEM_LIKELY_TO_HOP_MSEC)
+#define CHANNEL_TIMER_SYNC_MSEC   (frameAirTimeMsec + REMOTE_SYSTEM_LIKELY_TO_HOP_MSEC)
 
   //Determine if the remote has hopped or is likely to hop very soon
   if (rmtHopTimeMsec <= REMOTE_SYSTEM_LIKELY_TO_HOP_MSEC)
@@ -3260,7 +3260,7 @@ void syncChannelTimer()
     systemPrint(" Hops, ");
     systemPrint(msToNextHopRemote);
     systemPrint(" Nxt Hop - ");
-    systemPrint(txRxTimeMsec);
+    systemPrint(frameAirTimeMsec);
     systemPrint(" (TX + RX)");
     if (adjustment)
     {
diff --git a/Firmware/LoRaSerial_Firmware/States.ino b/Firmware/LoRaSerial_Firmware/States.ino
index 3d3e72f6..a217f9e1 100644
--- a/Firmware/LoRaSerial_Firmware/States.ino
+++ b/Firmware/LoRaSerial_Firmware/States.ino
@@ -766,7 +766,7 @@ void updateRadioState()
             COMPUTE_RX_TIME(rxData, 1);
 
             //The datagram we are expecting
-            syncChannelTimer(); //Adjust freq hop ISR based on remote's remaining clock
+            syncChannelTimer(txRxTimeMsec); //Adjust freq hop ISR based on remote's remaining clock
 
             triggerEvent(TRIGGER_RX_ACK);
 
@@ -1122,7 +1122,7 @@ void updateRadioState()
             COMPUTE_TIMESTAMP_OFFSET(rxData + 1, 0);
 
             //Server has responded with ACK
-            syncChannelTimer(); //Start and adjust freq hop ISR based on remote's remaining clock
+            syncChannelTimer(txRxTimeMsec); //Start and adjust freq hop ISR based on remote's remaining clock
 
             //Change to the server's channel number
             channelNumber = rxVcData[0];
@@ -1283,7 +1283,7 @@ void updateRadioState()
 
             //Sync clock if server sent the heartbeat
             if (settings.server == false)
-              syncChannelTimer(); //Adjust freq hop ISR based on remote's remaining clock
+              syncChannelTimer(txRxTimeMsec); //Adjust freq hop ISR based on remote's remaining clock
 
             frequencyCorrection += radio.getFrequencyError() / 1000000.0;
 
@@ -1299,7 +1299,7 @@ void updateRadioState()
 
             //Sync clock if server sent the datagram
             if (settings.server == false)
-              syncChannelTimer(); //Adjust freq hop ISR based on remote's remaining clock
+              syncChannelTimer(txRxTimeMsec); //Adjust freq hop ISR based on remote's remaining clock
 
             setHeartbeatMultipoint(); //We're sync'd so reset heartbeat timer
 
@@ -2914,7 +2914,7 @@ void vcReceiveHeartbeat(uint32_t rxMillis)
   int vcSrc;
 
   if (rxSrcVc == VC_SERVER)
-    syncChannelTimer(); //Adjust freq hop ISR based on server's remaining clock
+    syncChannelTimer(txRxTimeMsec); //Adjust freq hop ISR based on server's remaining clock
 
   //Update the timestamp offset
   if (rxSrcVc == VC_SERVER)

From 72e44927074c2d1e8d9550277983597c7f24ebb1 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Sun, 8 Jan 2023 14:52:33 -1000
Subject: [PATCH 11/25] Add channelTimer history

---
 .../LoRaSerial_Firmware.ino                   |  2 +
 Firmware/LoRaSerial_Firmware/Radio.ino        | 18 +++++--
 Firmware/LoRaSerial_Firmware/States.ino       | 52 +++++++++++++++++--
 Firmware/LoRaSerial_Firmware/settings.h       | 11 ++++
 4 files changed, 75 insertions(+), 8 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
index 62a31a3b..90c8e154 100644
--- a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
+++ b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
@@ -429,6 +429,8 @@ unsigned long radioStateHistory[RADIO_MAX_STATE];
 
 uint8_t packetLength = 0; //Total bytes received, used for calculating clock sync times in multi-point mode
 int16_t msToNextHopRemote; //Can become negative
+uint8_t clockSyncIndex;
+CLOCK_SYNC_DATA clockSyncData[16];
 
 bool requestYield = false; //Datagram sender can tell this radio to stop transmitting to enable two-way comm
 unsigned long yieldTimerStart = 0;
diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index 9d7d4dcb..d008d3ba 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -3075,7 +3075,6 @@ void syncChannelTimer(uint16_t frameAirTimeMsec)
   //the channelTimerStart value indicated that it was done.  The channel
   //timer update will add only microseconds to when the hop is done.
   delayedHopCount = timeToHop ? 1 : 0;
-  timeToHop = false;
 
   //The radios are using the same frequencies since the frame was successfully
   //received.  The goal is to adjust the channel timer to fire in close proximity
@@ -3235,20 +3234,31 @@ void syncChannelTimer(uint16_t frameAirTimeMsec)
   //When the ISR fires, reload the channel timer with settings.maxDwellTime
   reloadChannelTimer = true;
 
+  //Log the previous clock sync
+  clockSyncData[clockSyncIndex].msToNextHop = msToNextHop;
+  clockSyncData[clockSyncIndex].frameAirTimeMsec = frameAirTimeMsec;
+  clockSyncData[clockSyncIndex].msToNextHopRemote = msToNextHopRemote;
+  clockSyncData[clockSyncIndex].adjustment = adjustment;
+  clockSyncData[clockSyncIndex].delayedHopCount = delayedHopCount;
+  clockSyncData[clockSyncIndex].lclHopTimeMsec = lclHopTimeMsec;
+  clockSyncData[clockSyncIndex].timeToHop = timeToHop;
+  clockSyncIndex += 1;
+
   //Restart the channel timer
+  timeToHop = false;
   channelTimer.setInterval_MS(msToNextHop, channelTimerHandler); //Adjust our hardware timer to match our mate's
   digitalWrite(pin_hop_timer, channelNumber & 1);
   channelTimerStart = currentMillis;
   channelTimerMsec = msToNextHop; //syncChannelTimer update
   channelTimer.enableTimer();
 
-  //Trigger after adjustments to timer to avoid skew during debug
-  triggerEvent(TRIGGER_SYNC_CHANNEL_TIMER);
-
   //----------------------------------------------------------------------
   // Leave the critical section
   //----------------------------------------------------------------------
 
+  //Trigger after adjustments to timer to avoid skew during debug
+  triggerEvent(TRIGGER_SYNC_CHANNEL_TIMER);
+
   //Hop if the timer fired prior to disabling the timer, resetting the channelTimerStart value
   if (delayedHopCount)
     hopChannel(true, delayedHopCount);
diff --git a/Firmware/LoRaSerial_Firmware/States.ino b/Firmware/LoRaSerial_Firmware/States.ino
index a217f9e1..759b640e 100644
--- a/Firmware/LoRaSerial_Firmware/States.ino
+++ b/Firmware/LoRaSerial_Firmware/States.ino
@@ -1355,6 +1355,7 @@ void updateRadioState()
               systemPrintln("HEARTBEAT Timeout");
               outputSerialData(true);
             }
+            dumpClockSynchronization();
             changeState(RADIO_DISCOVER_BEGIN);
           }
         }
@@ -2615,6 +2616,43 @@ void displayRadioStateHistory()
   petWDT();
 }
 
+//Dump the clock synchronization data
+void dumpClockSynchronization()
+{
+  //Dump the clock sync data
+  petWDT();
+  for (uint8_t x = 0; x < (sizeof(clockSyncData) / sizeof(clockSyncData[0])); x++)
+  {
+    uint8_t index = (x + clockSyncIndex) % clockSyncIndex;
+    if (clockSyncData[index].frameAirTimeMsec)
+    {
+      systemPrint("Lcl: ");
+      systemPrint(clockSyncData[index].lclHopTimeMsec);
+      systemPrint(", Rmt: ");
+      systemPrint(clockSyncData[index].msToNextHopRemote);
+      systemPrint(" - ");
+      systemPrint(clockSyncData[index].frameAirTimeMsec);
+      systemPrint(" = ");
+      systemPrint(clockSyncData[index].msToNextHopRemote - clockSyncData[index].frameAirTimeMsec);
+      systemPrint(" + ");
+      systemPrint(clockSyncData[index].adjustment);
+      systemPrint(" = ");
+      systemPrint(clockSyncData[index].msToNextHop);
+      systemPrint(" msToNextHop");
+      if (clockSyncData[index].delayedHopCount)
+      {
+        systemPrint(", timeToHop: ");
+        systemPrint(clockSyncData[index].timeToHop);
+        systemPrint(", Hops: ");
+        systemPrint(clockSyncData[index].delayedHopCount);
+      }
+      systemPrintln();
+      outputSerialData(true);
+      petWDT();
+    }
+  }
+}
+
 //Break a point-to-point link
 void breakLink()
 {
@@ -2630,6 +2668,13 @@ void breakLink()
       linkDownTime += timestampOffset;
   }
   linkFailures++;
+
+  //Stop the ACK timer
+  STOP_ACK_TIMER();
+
+  //Dump the clock synchronization
+  dumpClockSynchronization();
+
   if (settings.printLinkUpDown)
   {
     if (settings.printTimestamp)
@@ -2640,13 +2685,12 @@ void breakLink()
     systemPrintln("--------- Link DOWN ---------");
     outputSerialData(true);
   }
-  triggerEvent(TRIGGER_RADIO_RESET);
-
-  //Stop the ACK timer
-  STOP_ACK_TIMER();
 
   //Flush the buffers
   resetSerial();
+
+  //Reset the radio and the link
+  triggerEvent(TRIGGER_RADIO_RESET);
   changeState(RADIO_RESET);
 }
 
diff --git a/Firmware/LoRaSerial_Firmware/settings.h b/Firmware/LoRaSerial_Firmware/settings.h
index cf1e1a40..694776e0 100644
--- a/Firmware/LoRaSerial_Firmware/settings.h
+++ b/Firmware/LoRaSerial_Firmware/settings.h
@@ -353,6 +353,17 @@ typedef enum
   //Add user LED types from 255 working down
 } LEDS_USE_TYPE;
 
+typedef struct _CLOCK_SYNC_DATA
+{
+  int16_t msToNextHopRemote;
+  uint16_t frameAirTimeMsec;
+  uint16_t msToNextHop;
+  int16_t lclHopTimeMsec;
+  int16_t adjustment;
+  int8_t delayedHopCount;
+  bool timeToHop;
+} CLOCK_SYNC_DATA;
+
 //These are all the settings that can be set on Serial Terminal Radio. It's recorded to NVM.
 typedef struct struct_settings {
   uint16_t sizeOfSettings = 0; //sizeOfSettings **must** be the first entry and must be int

From ca7dde8d9b9aff55cca8a2d1117982f7bc28f98b Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Sun, 8 Jan 2023 15:19:12 -1000
Subject: [PATCH 12/25] Add a trigger to measure the transmit time

---
 Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino |  1 +
 Firmware/LoRaSerial_Firmware/Radio.ino               | 12 +++++-------
 Firmware/LoRaSerial_Firmware/settings.h              |  1 +
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
index 90c8e154..b24d4afe 100644
--- a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
+++ b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
@@ -584,6 +584,7 @@ uint32_t rxTimeUsec;
 uint32_t txTimeUsec;
 uint16_t txRxTimeMsec;
 
+uint32_t txSetChannelTimerMicros; //Timestamp when millis is read in TX routine to set channel timer value
 uint32_t transactionCompleteMicros; //Timestamp at the beginning of the transactionCompleteIsr routine
 uint32_t txDatagramMicros; //Timestamp at the beginning of the transmitDatagram routine
 uint16_t maxFrameAirTime; //Air time of the maximum sized message
diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index d008d3ba..e6df726b 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -2490,6 +2490,10 @@ bool transmitDatagram()
     //Hake sure that the transmitted msToNextHop is in the range 0 - maxDwellTime
     if (timeToHop)
       hopChannel();
+
+    //Measure the time to the next hop
+    triggerEvent(TRIGGER_TX_LOAD_CHANNE_TIMER_VALUE);
+    txSetChannelTimerMicros = micros();
     unsigned long currentMillis = millis();
     uint16_t msToNextHop; //TX channel timer value
     if (channelTimerMsec)
@@ -2534,13 +2538,7 @@ bool transmitDatagram()
         {
           case DATAGRAM_DATA_ACK:
           case DATAGRAM_SYNC_CLOCKS:
-            systemPrint("TX: ");
-            systemPrint(channelTimerMsec);
-            systemPrint(" channelTimerMsec + (");
-            systemPrint(currentMillis);
-            systemPrint(" millis() - ");
-            systemPrint(channelTimerStart);
-            systemPrint(" channelTimerStart) = ");
+            systemPrint("TX msToNextHop: ");
             systemPrint(msToNextHop);
             systemPrintln(" mSec");
           break;
diff --git a/Firmware/LoRaSerial_Firmware/settings.h b/Firmware/LoRaSerial_Firmware/settings.h
index 694776e0..64f80453 100644
--- a/Firmware/LoRaSerial_Firmware/settings.h
+++ b/Firmware/LoRaSerial_Firmware/settings.h
@@ -286,6 +286,7 @@ enum
   TRIGGER_TX_DUPLICATE_ACK,
   TRIGGER_TX_FIND_PARTNER,
   TRIGGER_TX_HEARTBEAT,
+  TRIGGER_TX_LOAD_CHANNE_TIMER_VALUE,
   TRIGGER_TX_SPI_DONE,
   TRIGGER_TX_SYNC_CLOCKS,
   TRIGGER_TX_YIELD,

From 1743f9daf8706f3301d56d9ef36c93667210060b Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Sun, 8 Jan 2023 15:52:59 -1000
Subject: [PATCH 13/25] Compute the transmit times for SYNC_CLOCKS, HEARTBEAT
 and DATA_ACK

---
 .../LoRaSerial_Firmware.ino                   |  3 +
 Firmware/LoRaSerial_Firmware/States.ino       | 56 +++++++++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
index b24d4afe..e93d9d6b 100644
--- a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
+++ b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
@@ -586,6 +586,9 @@ uint16_t txRxTimeMsec;
 
 uint32_t txSetChannelTimerMicros; //Timestamp when millis is read in TX routine to set channel timer value
 uint32_t transactionCompleteMicros; //Timestamp at the beginning of the transactionCompleteIsr routine
+uint32_t txDataAckUsec; //Time in microseconds to transmit the DATA_ACK frame
+uint32_t txHeartbeatUsec; //Time in microseconds to transmit the HEARTBEAT frame
+uint32_t txSyncClockUsec; //Time in microseconds to transmit the SYNC_CLOCKS frame
 uint32_t txDatagramMicros; //Timestamp at the beginning of the transmitDatagram routine
 uint16_t maxFrameAirTime; //Air time of the maximum sized message
 unsigned long remoteSystemMillis; //Millis value contained in the received message
diff --git a/Firmware/LoRaSerial_Firmware/States.ino b/Firmware/LoRaSerial_Firmware/States.ino
index 759b640e..626262a3 100644
--- a/Firmware/LoRaSerial_Firmware/States.ino
+++ b/Firmware/LoRaSerial_Firmware/States.ino
@@ -488,6 +488,17 @@ void updateRadioState()
       //Determine if a SYNC_CLOCKS has completed transmission
       if (transactionComplete)
       {
+        //Compute the SYNC_CLOCKS frame transmit frame
+        if ((!txSyncClockUsec) && (txControl.datagramType == DATAGRAM_SYNC_CLOCKS))
+        {
+          txSyncClockUsec = transactionCompleteMicros - txSetChannelTimerMicros;
+          if (settings.debugSync)
+          {
+            systemPrint("txSyncClockUsec: ");
+            systemPrintln(txSyncClockUsec);
+          }
+        }
+
         COMPUTE_TX_TIME();
         triggerEvent(TRIGGER_TX_DONE);
         transactionComplete = false; //Reset ISR flag
@@ -661,6 +672,28 @@ void updateRadioState()
       {
         transactionComplete = false; //Reset ISR flag
 
+        //Compute the ACK frame transmit frame
+        if ((!txDataAckUsec) && (txControl.datagramType == DATAGRAM_HEARTBEAT))
+        {
+          txDataAckUsec = transactionCompleteMicros - txSetChannelTimerMicros;
+          if (settings.debugSync)
+          {
+            systemPrint("txDataAckUsec: ");
+            systemPrintln(txDataAckUsec);
+          }
+        }
+
+        //Compute the HEARTBEAT frame transmit frame
+        if ((!txHeartbeatUsec) && (txControl.datagramType == DATAGRAM_HEARTBEAT))
+        {
+          txHeartbeatUsec = transactionCompleteMicros - txSetChannelTimerMicros;
+          if (settings.debugSync)
+          {
+            systemPrint("txHeartbeatUsec: ");
+            systemPrintln(txHeartbeatUsec);
+          }
+        }
+
         //Determine if an ACK was transmitted
         if (txControl.datagramType = DATAGRAM_DATA_ACK)
         {
@@ -1374,6 +1407,29 @@ void updateRadioState()
       if (transactionComplete == true)
       {
         transactionComplete = false; //Reset ISR flag
+
+        //Compute the HEARTBEAT frame transmit frame
+        if ((!txHeartbeatUsec) && (txControl.datagramType == DATAGRAM_HEARTBEAT))
+        {
+          txHeartbeatUsec = transactionCompleteMicros - txSetChannelTimerMicros;
+          if (settings.debugSync)
+          {
+            systemPrint("txHeartbeatUsec: ");
+            systemPrintln(txHeartbeatUsec);
+          }
+        }
+
+        //Compute the SYNC_CLOCKS frame transmit frame
+        else if ((!txSyncClockUsec) && (txControl.datagramType == DATAGRAM_SYNC_CLOCKS))
+        {
+          txSyncClockUsec = transactionCompleteMicros - txSetChannelTimerMicros;
+          if (settings.debugSync)
+          {
+            systemPrint("txSyncClockUsec: ");
+            systemPrintln(txSyncClockUsec);
+          }
+        }
+
         returnToReceiving();
         changeState(RADIO_MP_STANDBY);
       }

From d962c67dcb555417a68368d155e187ba6c3ebb46 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Sun, 8 Jan 2023 17:58:27 -1000
Subject: [PATCH 14/25] Pass in the frame air time when computing the timestamp
 offset

---
 .../LoRaSerial_Firmware.ino                   |  2 ++
 Firmware/LoRaSerial_Firmware/States.ino       | 31 +++++++++----------
 2 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
index e93d9d6b..f1e2d81f 100644
--- a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
+++ b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
@@ -72,6 +72,8 @@ const int FIRMWARE_VERSION_MINOR = 0;
 #define P2P_ACK_BYTES           sizeof(unsigned long) //Number of data bytes in the ACK frame
 #define VC_HEARTBEAT_BYTES      0 //Number of data bytes in the VC_HEARTBEAT frame
 
+#define TX_TO_RX_USEC           680 //Time from TX to RX transactionComplete in microseconds
+
 //Bit 0: Signal Detected indicates that a valid LoRa preamble has been detected
 //Bit 1: Signal Synchronized indicates that the end of Preamble has been detected, the modem is in lock
 //Bit 3: Header Info Valid toggles high when a valid Header (with correct CRC) is detected
diff --git a/Firmware/LoRaSerial_Firmware/States.ino b/Firmware/LoRaSerial_Firmware/States.ino
index 626262a3..d425c548 100644
--- a/Firmware/LoRaSerial_Firmware/States.ino
+++ b/Firmware/LoRaSerial_Firmware/States.ino
@@ -48,15 +48,15 @@
     ackTimer = 0;             \
   }
 
-#define COMPUTE_TIMESTAMP_OFFSET(millisBuffer, rShift)                          \
-  {                                                                             \
-    unsigned long deltaUsec = txTimeUsec + rxTimeUsec;                          \
-    memcpy(&remoteSystemMillis, millisBuffer, sizeof(currentMillis));           \
-    timestampOffset = (remoteSystemMillis + (deltaUsec / 1000) - currentMillis);\
-    timestampOffset >>= rShift;                                                 \
+#define COMPUTE_TIMESTAMP_OFFSET(millisBuffer, rShift, frameAirTimeUsec)               \
+  {                                                                                    \
+    unsigned long deltaUsec = frameAirTimeUsec + micros() - transactionCompleteMicros; \
+    memcpy(&remoteSystemMillis, millisBuffer, sizeof(currentMillis));                  \
+    timestampOffset = (remoteSystemMillis + (deltaUsec / 1000) - currentMillis);       \
+    timestampOffset >>= rShift;                                                        \
   }
 
-#define COMPUTE_RX_TIME(millisBuffer, rShift)                                   \
+#define COMPUTE_RX_TIME(millisBuffer, rShift, frameAirTimeUsec)                 \
   {                                                                             \
     currentMillis = millis();                                                   \
     long deltaUsec = micros() - transactionCompleteMicros;                      \
@@ -80,7 +80,7 @@
     }                                                                           \
                                                                                 \
     /*Adjust the timestamp offset*/                                             \
-    COMPUTE_TIMESTAMP_OFFSET(millisBuffer, rShift);                             \
+    COMPUTE_TIMESTAMP_OFFSET(millisBuffer, rShift, frameAirTimeUsec);           \
   }
 
 #define COMPUTE_TX_TIME()                                                       \
@@ -328,7 +328,7 @@ void updateRadioState()
           case DATAGRAM_FIND_PARTNER:
             //Received FIND_PARTNER
             //Compute the receive time
-            COMPUTE_RX_TIME(rxData, 1);
+            COMPUTE_RX_TIME(rxData, 1, calcAirTimeUsec(headerBytes + P2P_FIND_PARTNER_BYTES + trailerBytes));
 
             //This system is the source of clock synchronization
             clockSyncReceiver = false; //P2P clock source
@@ -418,7 +418,7 @@ void updateRadioState()
           case DATAGRAM_FIND_PARTNER:
             //Received FIND_PARTNER
             //Compute the receive time
-            COMPUTE_RX_TIME(rxData + 1, 1);
+            COMPUTE_RX_TIME(rxData + 1, 1, calcAirTimeUsec(headerBytes + P2P_FIND_PARTNER_BYTES + trailerBytes));
 
             //Acknowledge the FIND_PARTNER
             triggerEvent(TRIGGER_TX_SYNC_CLOCKS);
@@ -439,7 +439,7 @@ void updateRadioState()
             }
 
             //Compute the receive time
-            COMPUTE_RX_TIME(rxData + 1, 1);
+            COMPUTE_RX_TIME(rxData + 1, 1, txSyncClockUsec);
 
             //Hop to the next channel
             hopChannel();
@@ -541,7 +541,7 @@ void updateRadioState()
           case DATAGRAM_ZERO_ACKS:
             //Received ACK 2
             //Compute the receive time
-            COMPUTE_RX_TIME(rxData, 1);
+            COMPUTE_RX_TIME(rxData, 1, calcAirTimeUsec(headerBytes + P2P_ZERO_ACKS_BYTES + trailerBytes));
 
             setHeartbeatLong(); //We sent SYNC_CLOCKS and they sent ZERO_ACKS, so don't be the first to send heartbeat
 
@@ -772,7 +772,7 @@ void updateRadioState()
           case DATAGRAM_HEARTBEAT:
             //Received heartbeat while link was idle. Send ack to sync clocks.
             //Adjust the timestamp offset
-            COMPUTE_TIMESTAMP_OFFSET(rxData, 1);
+            COMPUTE_TIMESTAMP_OFFSET(rxData, 1, txHeartbeatUsec);
             triggerEvent(TRIGGER_RX_HEARTBEAT);
             blinkHeartbeatLed(true);
 
@@ -796,7 +796,7 @@ void updateRadioState()
 
           case DATAGRAM_DATA_ACK:
             //Adjust the timestamp offset
-            COMPUTE_RX_TIME(rxData, 1);
+            COMPUTE_RX_TIME(rxData, 1, txDataAckUsec);
 
             //The datagram we are expecting
             syncChannelTimer(txRxTimeMsec); //Adjust freq hop ISR based on remote's remaining clock
@@ -1152,7 +1152,7 @@ void updateRadioState()
 
             //Compute the common clock
             currentMillis = millis();
-            COMPUTE_TIMESTAMP_OFFSET(rxData + 1, 0);
+            COMPUTE_TIMESTAMP_OFFSET(rxData + 1, 0, txTimeUsec + rxTimeUsec);
 
             //Server has responded with ACK
             syncChannelTimer(txRxTimeMsec); //Start and adjust freq hop ISR based on remote's remaining clock
@@ -1172,7 +1172,6 @@ void updateRadioState()
             frequencyCorrection += radio.getFrequencyError() / 1000000.0;
 
             lastPacketReceived = millis(); //Reset
-
             changeState(RADIO_MP_STANDBY);
             break;
         }

From c3843dc3354acc121dc4a677dfa997ad78ec5250 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Mon, 9 Jan 2023 06:05:36 -1000
Subject: [PATCH 15/25] Rename FrameTimeout to SerialDelay and move to serial
 settings

---
 Firmware/LoRaSerial_Firmware/Commands.ino | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Firmware/LoRaSerial_Firmware/Commands.ino b/Firmware/LoRaSerial_Firmware/Commands.ino
index ad2b3528..4ac6950f 100644
--- a/Firmware/LoRaSerial_Firmware/Commands.ino
+++ b/Firmware/LoRaSerial_Firmware/Commands.ino
@@ -1102,7 +1102,6 @@ const COMMAND_ENTRY commands[] =
   {'R',   0,   1,    0,   1,    0, TYPE_BOOL,         valInt,         "EncryptData",          &tempSettings.encryptData},
   {'R',   0,   1,    0,   0,    0, TYPE_KEY,          valKey,         "EncryptionKey",        &tempSettings.encryptionKey},
   {'R',   0,   0,    0, 255,    0, TYPE_U8,           valInt,         "FramesToYield",        &tempSettings.framesToYield},
-  {'R',   0,   0,   10, 2000,   0, TYPE_U16,          valInt,         "FrameTimeout",         &tempSettings.serialTimeoutBeforeSendingFrame_ms},
   {'R',   0,   0,  250, 65535,  0, TYPE_U16,          valInt,         "HeartBeatTimeout",     &tempSettings.heartbeatTimeout},
   {'R',   0,   0,    0, 255,    0, TYPE_U8,           valInt,         "MaxResends",           &tempSettings.maxResends},
   {'R',   0,   1,    0, 255,    0, TYPE_U8,           valInt,         "NetID",                &tempSettings.netID},
@@ -1118,6 +1117,7 @@ const COMMAND_ENTRY commands[] =
   {'S',   0,   0,    0,   1,    0, TYPE_BOOL,         valInt,         "FlowControl",          &tempSettings.flowControl},
   {'S',   0,   0,    0,   1,    0, TYPE_BOOL,         valInt,         "InvertCts",            &tempSettings.invertCts},
   {'S',   0,   0,    0,   1,    0, TYPE_BOOL,         valInt,         "InvertRts",            &tempSettings.invertRts},
+  {'S',   0,   0,   10, 2000,   0, TYPE_U16,          valInt,         "SerialDelay",          &tempSettings.serialTimeoutBeforeSendingFrame_ms},
   {'S',   0,   0,    0,   0,    0, TYPE_SPEED_SERIAL, valSpeedSerial, "SerialSpeed",          &tempSettings.serialSpeed},
   {'S',   0,   0,    0,   1,    0, TYPE_BOOL,         valInt,         "UsbSerialWait",        &tempSettings.usbSerialWait},
 

From cf5f7bf6f590f2e119a5f37f03e73ee1069382b6 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Mon, 9 Jan 2023 06:10:54 -1000
Subject: [PATCH 16/25] Move overheadTime from being a radio parameter to being
 a debug param

---
 Firmware/LoRaSerial_Firmware/Commands.ino | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Firmware/LoRaSerial_Firmware/Commands.ino b/Firmware/LoRaSerial_Firmware/Commands.ino
index 4ac6950f..eeeb144b 100644
--- a/Firmware/LoRaSerial_Firmware/Commands.ino
+++ b/Firmware/LoRaSerial_Firmware/Commands.ino
@@ -1068,6 +1068,7 @@ const COMMAND_ENTRY commands[] =
   {'D',   1,   0,    0,   1,    0, TYPE_BOOL,         valInt,         "DebugTransmit",        &tempSettings.debugTransmit},
   {'D',   1,   0,    0,   1,    0, TYPE_BOOL,         valInt,         "DebugSerial",          &tempSettings.debugSerial},
   {'D',   1,   0,    0,   1,    0, TYPE_BOOL,         valInt,         "DisplayRealMillis",    &tempSettings.displayRealMillis},
+  {'D',   0,   1,    0, 1000,   0, TYPE_U16,          valInt,         "OverHeadtime",         &tempSettings.overheadTime},
   {'D',   1,   0,    0,   1,    0, TYPE_BOOL,         valInt,         "PrintAckNumbers",      &tempSettings.printAckNumbers},
   {'D',   1,   0,    0,   1,    0, TYPE_BOOL,         valInt,         "PrintChannel",         &tempSettings.printChannel},
   {'D',   1,   0,    0,   1,    0, TYPE_BOOL,         valInt,         "PrintFrequency",       &tempSettings.printFrequency},
@@ -1106,7 +1107,6 @@ const COMMAND_ENTRY commands[] =
   {'R',   0,   0,    0, 255,    0, TYPE_U8,           valInt,         "MaxResends",           &tempSettings.maxResends},
   {'R',   0,   1,    0, 255,    0, TYPE_U8,           valInt,         "NetID",                &tempSettings.netID},
   {'R',   0,   1,    0,   2,    0, TYPE_U8,           valInt,         "OperatingMode",        &tempSettings.operatingMode},
-  {'R',   0,   1,    0, 1000,   0, TYPE_U16,          valInt,         "OverHeadtime",         &tempSettings.overheadTime},
   {'R',   0,   0,    0,   1,    0, TYPE_BOOL,         valServer,      "Server",               &tempSettings.server},
   {'R',   0,   1,    0,   1,    0, TYPE_BOOL,         valInt,         "VerifyRxNetID",        &tempSettings.verifyRxNetID},
 

From 390c62bc9463e8c1fedb3ac4a61b51c3c03a046c Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Mon, 9 Jan 2023 06:03:32 -1000
Subject: [PATCH 17/25] Describe the steps to prevent attacks on the LoRaSerial
 network

---
 Firmware/LoRaSerial_Firmware/Radio.ino | 104 +++++++++++++++++++++++++
 1 file changed, 104 insertions(+)

diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index e6df726b..543528fc 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -1536,6 +1536,110 @@ bool xmitVcZeroAcks(int8_t destVc)
 
 //=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 //Datagram reception
+//
+//Security or lack there of:
+//
+//The comments below outline the radio parameters and how they can be determined by
+//listening to the radio traffic.  The required parameters are followed by one or
+//more step numbers indicating the step which determines the parameter's value.  The
+//comments further describe the steps that can be taken to reduce the attack surface
+//for the LoRaSerial network.
+//
+//The following settings define the LoRaSerial radio network:
+//
+//    AirSpeed - 3, 4, 5
+//    AutoTune - This is receive only
+//    Bandwidth - 3
+//    CodingRate - 5
+//    FrequencyHop - 1
+//    FrequencyMax - 1
+//    FrequencyMin - 1
+//    MaxDwellTime - 1
+//    NumberOfChannels - 1
+//    PreambleLength - 4
+//    SpreadFactor - 4
+//    SyncWord - 4
+//    TxPower
+//
+//  Protocol settings:
+//
+//    DataScrambling - 6
+//    EnableCRC16 - 8
+//    EncryptData - 7
+//    EncryptionKey - 7
+//    FramesToYield
+//    HeartBeatTimeout - 12
+//    MaxResends - 14
+//    NetID - 9
+//    OperatingMode - 10, 11
+//    Server - 10, 11
+//    VerifyRxNetID - 9
+//
+//Attempting to attack a network of LoRaSerial radios would be done with the following
+//steps:
+//
+// 1. Locate the frequencies that the network is using
+//    a. Listen for traffic on a specific channel to determine if the network is using
+//       that channel
+//    b. Repeat across all of the channels in the available frequency band
+// 2. Once the frequencies are identified, attempt to determine the channel sequence
+//    by monitoring when traffic occurs on each of the identified frequencies, this
+//    allows the attacker to construct the hop table for the network
+// 3. Look at the bandwidth utilized by the radio network.  The signal for each
+//    symbol is a ramp that spans the bandwidth selected for use
+// 4. Using a receiver that uses the opposite ramp to generate the sub frequencies
+//    within the bandwidth to decode the symbols.  By monitoring the network traffic
+//    it is possible to determine the spreadfactor since there are 2^SF sub frequencies
+//    that will be used within the bandwidth
+// 5. Now that the spread factor is known, the next step is to determine the coding
+//    rate used for forward error correction.  Here 4 data bits are converted into
+//    between 5 to 8 bits in the transmitted frame
+// 6. Look at the signal for multiple transmissions, does this signal have a DC offset?
+//    The data scrambling setting is false if a DC offset is present, or is true when
+//    no DC offset is present
+// 7. Next step is breaking the encryption key
+// 8. After the encryption key is obtained, it is possible determine if the link is
+//    using software CRC by computing the CRC-16 value on the first n-2 bytes and
+//    comparing that with the last 2 bytes
+// 9. Determine if the link is using a network ID value, by checking the first byte
+//    in each of the transmitted frames
+// 10. Determine if the virtual circuit header is contained in the transmitted frames
+// 11. Determine which set of data frames are being transmitted
+// 12. Determine the maximum interval between HEARTBEAT frames to roughly determine
+//     the HeartbeatTimeout value
+// 13. Look for HEARTBEAT frames and FIND_PARTNER frames.  A FIND_PARTNER frame
+//     is sent following a link failure which occurs after three HEARTBEAT timeout
+//     periods.
+// 14. The MaxResends value can be estimated by the maximum number of data
+//     retransmissions done prior to the link failure.  A large number of link
+//     failures will need to be collected from a very radio near the network.
+//
+//How do you prevent the attacks on a LoRaSerial radio network:
+//
+// 1. Don't advertize the network.  Reduce the TxPower value to the minimum needed
+//    to successfully operate the network
+//
+// 2. Encrypt the data on the network.  Don't use the factory default encryption key.
+//    Select a new encryption key and and train all of the radios in the network with
+//    this key.  This will prevent attacks from any groups that are not able to break
+//    the encryption.  However the radio network is vulnerable to well funded or
+//    dedicated groups that are able to break the encryption.
+//
+// 3. Change the encryption key. When another network is using the same encryption key
+//    and same network ID traffic from the other network is likely to be received.
+//    Selecting another encryption key will avoid this behavior.  Also the encryption
+//    key may be tested by setting a radio to MODE_MULTIPOINT, disabling VerifyRxNetID
+//    and disabling EnableCRC16.  Both settings of DataScrambling will need to be tested.
+//
+// 4. Use a network ID.  This won't prevent attacks, but it prevents the reception
+//    of frames from other networks use the same encryption key.
+//
+// 5. Use software CRC-16.  This won't prevent attacks but will eliminate most
+//    frames from networks using the same encryption key that don't use a network
+//    ID.  Occasionally, when they get lucky, our network ID matches the first byte
+//    of their transmitted frame.  The software CRC-16 will most likely cause this
+//    frame to be discarded.
+//
 //=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 
 //Determine the type of datagram received

From 267b183304a61ff07bd52047fca525ad1a0f2bbd Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Mon, 9 Jan 2023 09:55:40 -1000
Subject: [PATCH 18/25] Output the correct channelNumber LSB on port A1 in
 syncChannelTimer

---
 Firmware/LoRaSerial_Firmware/Radio.ino | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index 543528fc..d2b8da17 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -3349,7 +3349,7 @@ void syncChannelTimer(uint16_t frameAirTimeMsec)
   //Restart the channel timer
   timeToHop = false;
   channelTimer.setInterval_MS(msToNextHop, channelTimerHandler); //Adjust our hardware timer to match our mate's
-  digitalWrite(pin_hop_timer, channelNumber & 1);
+  digitalWrite(pin_hop_timer, ((channelNumber + delayedHopCount) % settings.numberOfChannels) & 1);
   channelTimerStart = currentMillis;
   channelTimerMsec = msToNextHop; //syncChannelTimer update
   channelTimer.enableTimer();

From 3ba72d3306d0b1bf4f9e6d056641097161477673 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Mon, 9 Jan 2023 10:00:25 -1000
Subject: [PATCH 19/25] Display the ACK, HEARTBEAT and SYNC_CLOCKS transmit
 times with ATI10

---
 Firmware/LoRaSerial_Firmware/Commands.ino | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/Commands.ino b/Firmware/LoRaSerial_Firmware/Commands.ino
index eeeb144b..2bd08c72 100644
--- a/Firmware/LoRaSerial_Firmware/Commands.ino
+++ b/Firmware/LoRaSerial_Firmware/Commands.ino
@@ -411,15 +411,14 @@ bool commandAT(const char * commandString)
 
         //Clock synchronization
         systemPrintln("    Clock Synchronization");
-        systemPrint("        TX Time: ");
-        systemPrint(txTimeUsec / 1000., 4);
-        systemPrintln(" mSec");
-        systemPrint("        RX Time: ");
-        systemPrint(rxTimeUsec / 1000., 4);
-        systemPrintln(" mSec");
-        systemPrint("        Total Time: ");
-        systemPrint((txTimeUsec + rxTimeUsec) / 1000., 5);
-        systemPrintln(" mSec");
+        systemPrint("        ACK Time: ");
+        systemPrint(txDataAckUsec);
+        systemPrint("        HEARTBEAT Time: ");
+        systemPrint(txHeartbeatUsec);
+        systemPrintln(" uSec");
+        systemPrint("        SYNC_CLOCKS Time: ");
+        systemPrint(txSyncClockUsec);
+        systemPrintln(" uSec");
         systemPrint("        Uptime: ");
         deltaMillis = millis();
         systemPrintTimestamp(deltaMillis);

From 4969ce6aad4f7d11950f3b97bda192153472b4bc Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Mon, 9 Jan 2023 10:04:26 -1000
Subject: [PATCH 20/25] Update the VC HEARTBEAT diagram

---
 Firmware/LoRaSerial_Firmware/Radio.ino | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index d2b8da17..5819129d 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -1384,14 +1384,14 @@ bool xmitVcHeartbeat(int8_t addr, uint8_t * id)
   *txData = (uint8_t)(endOfTxData - txData);
 
   /*
-                                                                              endOfTxData ---.
-                                                                                             |
-                                                                                             V
-      +----------+---------+----------+------------+----------+---------+----------+---------+----------+
-      | Optional |         | Optional | Optional   |          |         |          |         | Optional |
-      | NET ID   | Control | C-Timer  | SF6 Length | DestAddr | SrcAddr | Src ID   | millis  | Trailer  |
-      | 8 bits   | 8 bits  | 2 bytes  | 8 bits     | 8 bits   | 8 bits  | 16 Bytes | 4 Bytes | n Bytes  |
-      +----------+---------+----------+------------+----------+---------+----------+---------+----------+
+                                                                                         endOfTxData ---.
+                                                                                                        |
+                                                                                                        V
+      +----------+---------+----------+------------+----------+----------+---------+----------+---------+----------+
+      | Optional |         | Optional | Optional   |          |          |         |          |         | Optional |
+      | NET ID   | Control | C-Timer  | SF6 Length |  Length  | DestAddr | SrcAddr | Src ID   | millis  | Trailer  |
+      | 8 bits   | 8 bits  | 2 bytes  | 8 bits     |  8 bits  | 8 bits   | 8 bits  | 16 Bytes | 4 Bytes | n Bytes  |
+      +----------+---------+----------+------------+----------+----------+---------+----------+---------+----------+
   */
 
   //Verify the data length

From 436d504d3cfee251990d2d66259e262db1904f9e Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Mon, 9 Jan 2023 10:12:22 -1000
Subject: [PATCH 21/25] Properly set the VC_HEARTBEAT_BYTES value

---
 Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
index f1e2d81f..a7d2cda9 100644
--- a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
+++ b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
@@ -70,7 +70,7 @@ const int FIRMWARE_VERSION_MINOR = 0;
 #define P2P_ZERO_ACKS_BYTES     sizeof(unsigned long) //Number of data bytes in the ZERO_ACKS frame
 #define P2P_HEARTBEAT_BYTES     sizeof(unsigned long) //Number of data bytes in the HEARTBEAT frame
 #define P2P_ACK_BYTES           sizeof(unsigned long) //Number of data bytes in the ACK frame
-#define VC_HEARTBEAT_BYTES      0 //Number of data bytes in the VC_HEARTBEAT frame
+#define VC_HEARTBEAT_BYTES      1 + 1 + 1 + 16 + 4 //Number of data bytes in the VC_HEARTBEAT frame
 
 #define TX_TO_RX_USEC           680 //Time from TX to RX transactionComplete in microseconds
 

From fb6f8fcd9d4c547eaedd0e6bc811b04db96df34b Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Mon, 9 Jan 2023 10:18:52 -1000
Subject: [PATCH 22/25] Add virtual-circuit triggers for TX and RX

---
 Firmware/LoRaSerial_Firmware/States.ino | 31 +++++++++++++++++++++----
 Firmware/LoRaSerial_Firmware/settings.h | 10 ++++++++
 2 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/States.ino b/Firmware/LoRaSerial_Firmware/States.ino
index d425c548..cc663da3 100644
--- a/Firmware/LoRaSerial_Firmware/States.ino
+++ b/Firmware/LoRaSerial_Firmware/States.ino
@@ -1867,6 +1867,8 @@ void updateRadioState()
             break;
 
           case DATAGRAM_DATA:
+            triggerEvent(TRIGGER_RX_DATA);
+
             //Move the data into the serial output buffer
             if (settings.debugSerial)
             {
@@ -1884,6 +1886,8 @@ void updateRadioState()
             break;
 
           case DATAGRAM_DATAGRAM:
+            triggerEvent(TRIGGER_RX_DATAGRAM);
+
             //Move the data into the serial output buffer
             if (settings.debugSerial)
             {
@@ -1899,6 +1903,7 @@ void updateRadioState()
             break;
 
           case DATAGRAM_DATA_ACK:
+            triggerEvent(TRIGGER_RX_ACK);
             vcSendPcAckNack(rexmtTxDestVc, true);
             STOP_ACK_TIMER();
             break;
@@ -1916,6 +1921,7 @@ void updateRadioState()
           //Second step in the 3-way handshake, received UNKNOWN_ACKS, respond
           //with SYNC_ACKS
           case DATAGRAM_VC_UNKNOWN_ACKS:
+            triggerEvent(TRIGGER_RX_VC_UNKNOWN_ACKS);
             if (xmitVcSyncAcks(rxSrcVc))
               changeState(RADIO_VC_WAIT_TX_DONE);
             vcChangeState(rxSrcVc, VC_STATE_WAIT_ZERO_ACKS);
@@ -1924,6 +1930,7 @@ void updateRadioState()
 
           //Third step in the 3-way handshake, received SYNC_ACKS, respond with ZERO_ACKS
           case DATAGRAM_VC_SYNC_ACKS:
+            triggerEvent(TRIGGER_RX_VC_SYNC_ACKS);
             if (xmitVcZeroAcks(rxSrcVc))
             {
               changeState(RADIO_VC_WAIT_TX_DONE);
@@ -1934,11 +1941,13 @@ void updateRadioState()
 
           //Last step in the 3-way handshake, received ZERO_ACKS, done
           case DATAGRAM_VC_ZERO_ACKS:
+            triggerEvent(TRIGGER_RX_VC_ZERO_ACKS);
             vcZeroAcks(rxSrcVc);
             vcChangeState(rxSrcVc, VC_STATE_CONNECTED);
             break;
 
           case DATAGRAM_REMOTE_COMMAND:
+            triggerEvent(TRIGGER_RX_COMMAND);
             rmtCmdVc = rxSrcVc;
 
             //Copy the command into the command buffer
@@ -1984,6 +1993,8 @@ void updateRadioState()
             break;
 
           case DATAGRAM_REMOTE_COMMAND_RESPONSE:
+            triggerEvent(TRIGGER_RX_COMMAND_RESPONSE);
+
             //Debug the serial path
             if (settings.debugSerial)
             {
@@ -2022,7 +2033,7 @@ void updateRadioState()
           //Send another heartbeat
           if (xmitVcHeartbeat(myVc, myUniqueId))
           {
-            triggerEvent(TRIGGER_TX_HEARTBEAT);
+            triggerEvent(TRIGGER_TX_VC_HEARTBEAT);
             if (((uint8_t)myVc) < MAX_VC)
               virtualCircuitList[myVc].lastTrafficMillis = currentMillis;
             changeState(RADIO_VC_WAIT_TX_DONE);
@@ -2147,6 +2158,7 @@ void updateRadioState()
                 //Send the UNKNOWN_ACKS datagram, first part of the 3-way handshake
                 if (xmitVcUnknownAcks(index))
                 {
+                  triggerEvent(TRIGGER_RX_VC_UNKNOWN_ACKS);
                   vcChangeState(index, VC_STATE_WAIT_SYNC_ACKS);
                   virtualCircuitList[index].timerMillis = datagramTimer;
                   changeState(RADIO_VC_WAIT_TX_DONE);
@@ -2163,6 +2175,7 @@ void updateRadioState()
                   //Retransmit the UNKNOWN_ACKS
                   if (xmitVcUnknownAcks(index))
                   {
+                    triggerEvent(TRIGGER_RX_VC_UNKNOWN_ACKS);
                     virtualCircuitList[index].timerMillis = datagramTimer;
                     changeState(RADIO_VC_WAIT_TX_DONE);
                   }
@@ -2179,6 +2192,7 @@ void updateRadioState()
                   //Retransmit the SYNC_CLOCKS
                   if (xmitVcSyncAcks(index))
                   {
+                    triggerEvent(TRIGGER_RX_VC_SYNC_ACKS);
                     virtualCircuitList[index].timerMillis = datagramTimer;
                     changeState(RADIO_VC_WAIT_TX_DONE);
                   }
@@ -2210,15 +2224,20 @@ void updateRadioState()
               if (vcHeader->destVc == VC_BROADCAST)
               {
                 //Broadcast this data to all VCs, no ACKs will be received
-                triggerEvent(TRIGGER_TX_DATA);
-                xmitVcDatagram();
+                if (xmitVcDatagram())
+                {
+                  triggerEvent(TRIGGER_TX_DATA);
+                  changeState(RADIO_VC_WAIT_TX_DONE);
+                }
                 break;
               }
 
               //Transmit the packet
-              triggerEvent(TRIGGER_TX_DATA);
               if (xmitDatagramP2PData() == true)
+              {
+                triggerEvent(TRIGGER_TX_DATA);
                 changeState(RADIO_VC_WAIT_TX_DONE);
+              }
 
               START_ACK_TIMER();
 
@@ -2289,7 +2308,10 @@ void updateRadioState()
               //Send the remote command
               vcHeader->destVc &= VCAB_NUMBER_MASK;
               if (xmitDatagramP2PCommand() == true)
+              {
+                triggerEvent(TRIGGER_TX_COMMAND);
                 changeState(RADIO_VC_WAIT_TX_DONE);
+              }
 
               START_ACK_TIMER();
 
@@ -3027,6 +3049,7 @@ void vcReceiveHeartbeat(uint32_t rxMillis)
     memcpy(&timestampOffset, &rxVcData[UNIQUE_ID_BYTES], sizeof(timestampOffset));
     timestampOffset += vcTxHeartbeatMillis + rxMillis - millis();
   }
+  triggerEvent(TRIGGER_RX_VC_HEARTBEAT);
 
   //Save our address
   if ((myVc == VC_UNASSIGNED) && (memcmp(myUniqueId, rxVcData, UNIQUE_ID_BYTES) == 0))
diff --git a/Firmware/LoRaSerial_Firmware/settings.h b/Firmware/LoRaSerial_Firmware/settings.h
index 64f80453..33e7257a 100644
--- a/Firmware/LoRaSerial_Firmware/settings.h
+++ b/Firmware/LoRaSerial_Firmware/settings.h
@@ -263,10 +263,15 @@ enum
   TRIGGER_RX_COMMAND,
   TRIGGER_RX_COMMAND_RESPONSE,
   TRIGGER_RX_DATA,
+  TRIGGER_RX_DATAGRAM,
   TRIGGER_RX_FIND_PARTNER,
   TRIGGER_RX_HEARTBEAT,
   TRIGGER_RX_SPI_DONE,
   TRIGGER_RX_SYNC_CLOCKS,
+  TRIGGER_RX_VC_HEARTBEAT,
+  TRIGGER_RX_VC_SYNC_ACKS,
+  TRIGGER_RX_VC_UNKNOWN_ACKS,
+  TRIGGER_RX_VC_ZERO_ACKS,
   TRIGGER_RX_YIELD,
   TRIGGER_RX_ZERO_ACKS,
   TRIGGER_SYNC_CHANNEL_TIMER,
@@ -282,6 +287,7 @@ enum
   TRIGGER_TX_COMMAND,
   TRIGGER_TX_COMMAND_RESPONSE,
   TRIGGER_TX_DATA,
+  TRIGGER_TX_DATAGRAM,
   TRIGGER_TX_DONE,
   TRIGGER_TX_DUPLICATE_ACK,
   TRIGGER_TX_FIND_PARTNER,
@@ -289,6 +295,10 @@ enum
   TRIGGER_TX_LOAD_CHANNE_TIMER_VALUE,
   TRIGGER_TX_SPI_DONE,
   TRIGGER_TX_SYNC_CLOCKS,
+  TRIGGER_TX_VC_HEARTBEAT,
+  TRIGGER_TX_VC_SYNC_ACKS,
+  TRIGGER_TX_VC_UNKNOWN_ACKS,
+  TRIGGER_TX_VC_ZERO_ACKS,
   TRIGGER_TX_YIELD,
   TRIGGER_TX_ZERO_ACKS,
   TRIGGER_UNKNOWN_PACKET,

From 79da1cc80db3f5d8054ea90fde2c30618924b123 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Mon, 9 Jan 2023 10:22:11 -1000
Subject: [PATCH 23/25] Virtual Circuit: Synchronize channel timer using the
 VC_HEARTBEAT frame

---
 Firmware/LoRaSerial_Firmware/States.ino | 70 ++++++++++++++++++-------
 1 file changed, 52 insertions(+), 18 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/States.ino b/Firmware/LoRaSerial_Firmware/States.ino
index cc663da3..c3334279 100644
--- a/Firmware/LoRaSerial_Firmware/States.ino
+++ b/Firmware/LoRaSerial_Firmware/States.ino
@@ -187,36 +187,45 @@ void updateRadioState()
 
       //Start the link between the radios
       if (settings.operatingMode == MODE_POINT_TO_POINT)
+      {
         changeState(RADIO_P2P_LINK_DOWN);
-      else if (settings.operatingMode == MODE_VIRTUAL_CIRCUIT)
+        break;
+      }
+
+      //Virtual circuit mode
+      if (settings.operatingMode == MODE_VIRTUAL_CIRCUIT)
       {
         if (settings.server)
         {
           //Reserve the server's address (0)
           myVc = vcIdToAddressByte(VC_SERVER, myUniqueId);
           clockSyncReceiver = false; //VC server is clock source
+          if (settings.frequencyHop)
+            startChannelTimer();
+
+          //Start sending heartbeats
+          xmitVcHeartbeat(myVc, myUniqueId);
+          changeState(RADIO_VC_WAIT_TX_DONE);
+          break;
         }
-        else
-          //Unknown client address
-          myVc = VC_UNASSIGNED;
+
+        //Unknown client address
+        myVc = VC_UNASSIGNED;
 
         //Start sending heartbeats
-        xmitVcHeartbeat(myVc, myUniqueId);
-        changeState(RADIO_VC_WAIT_TX_DONE);
+        changeState(RADIO_VC_WAIT_SERVER);
+        break;
       }
-      else
+
+      //Multipoint mode
+      if (settings.server == true)
       {
-        if (settings.server == true)
-        {
-          clockSyncReceiver = false; //Multipoint server is clock source
-          startChannelTimer(); //Start hopping - multipoint clock source
-          changeState(RADIO_MP_STANDBY);
-        }
-        else
-        {
-          changeState(RADIO_DISCOVER_BEGIN);
-        }
+        clockSyncReceiver = false; //Multipoint server is clock source
+        startChannelTimer(); //Start hopping - multipoint clock source
+        changeState(RADIO_MP_STANDBY);
       }
+      else
+        changeState(RADIO_DISCOVER_BEGIN);
       break;
 
     //=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
@@ -1780,12 +1789,21 @@ void updateRadioState()
     //Wait for a HEARTBEAT from the server
     //====================
     case RADIO_VC_WAIT_SERVER:
+      //The server should never be in this state
       if (myVc == VC_SERVER)
       {
         changeState(RADIO_VC_WAIT_RECEIVE);
         break;
       }
 
+      //Stop the frequency hopping
+      stopChannelTimer();
+      if (channelNumber != 0)
+      {
+        channelNumber = 0;
+        setRadioFrequency(false);
+      }
+
       //If dio0ISR has fired, a packet has arrived
       currentMillis = millis();
       if (transactionComplete == true)
@@ -1796,6 +1814,11 @@ void updateRadioState()
         //Process the received datagram
         if ((packetType == DATAGRAM_VC_HEARTBEAT) && (rxSrcVc == VC_SERVER))
         {
+          //Start the channel timer
+          startChannelTimer();
+          channelTimerStart -= settings.maxDwellTime;
+
+          //Synchronize the channel timer with the server
           vcReceiveHeartbeat(millis() - currentMillis);
           changeState(RADIO_VC_WAIT_RECEIVE);
         }
@@ -1818,6 +1841,17 @@ void updateRadioState()
       {
         transactionComplete = false;
 
+        //Compute the HEARTBEAT frame transmit frame
+        if ((!txHeartbeatUsec) && (txControl.datagramType == DATAGRAM_HEARTBEAT))
+        {
+          txHeartbeatUsec = transactionCompleteMicros - txSetChannelTimerMicros;
+          if (settings.debugSync)
+          {
+            systemPrint("txHeartbeatUsec: ");
+            systemPrintln(txHeartbeatUsec);
+          }
+        }
+
         //Indicate that the transmission is complete
         triggerEvent(TRIGGER_TX_DONE);
 
@@ -3034,7 +3068,7 @@ void vcReceiveHeartbeat(uint32_t rxMillis)
   uint32_t deltaMillis;
   int vcSrc;
 
-  if (rxSrcVc == VC_SERVER)
+  if ((rxSrcVc == VC_SERVER) || (memcmp(rxVcData, myUniqueId, sizeof(myUniqueId)) == 0))
     syncChannelTimer(txRxTimeMsec); //Adjust freq hop ISR based on server's remaining clock
 
   //Update the timestamp offset

From eb033a5eee89f4258a2b617f05de8726ddbde6c6 Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Sun, 8 Jan 2023 17:17:30 -1000
Subject: [PATCH 24/25] Add DATA_ACK, HEARTBEAT and SYNC_CLOCKS air time in
 mSec to SYNC_CLOCKS

---
 .../LoRaSerial_Firmware.ino                   |  2 +-
 Firmware/LoRaSerial_Firmware/Radio.ino        | 25 +++++++++++++------
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
index a7d2cda9..b3ab6c2e 100644
--- a/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
+++ b/Firmware/LoRaSerial_Firmware/LoRaSerial_Firmware.ino
@@ -66,7 +66,7 @@ const int FIRMWARE_VERSION_MINOR = 0;
 //Frame lengths
 #define MP_HEARTBEAT_BYTES      0 //Number of data bytes in the MP_HEARTBEAT frame
 #define P2P_FIND_PARTNER_BYTES  sizeof(unsigned long) //Number of data bytes in the FIND_PARTNER frame
-#define P2P_SYNC_CLOCKS_BYTES   (sizeof(uint8_t) + sizeof(unsigned long)) //Number of data bytes in the SYNC_CLOCKS frame
+#define P2P_SYNC_CLOCKS_BYTES   (sizeof(uint8_t) + sizeof(unsigned long) + sizeof(uint32_t) + sizeof(uint32_t) + sizeof(uint32_t)) //Number of data bytes in the SYNC_CLOCKS frame
 #define P2P_ZERO_ACKS_BYTES     sizeof(unsigned long) //Number of data bytes in the ZERO_ACKS frame
 #define P2P_HEARTBEAT_BYTES     sizeof(unsigned long) //Number of data bytes in the HEARTBEAT frame
 #define P2P_ACK_BYTES           sizeof(unsigned long) //Number of data bytes in the ACK frame
diff --git a/Firmware/LoRaSerial_Firmware/Radio.ino b/Firmware/LoRaSerial_Firmware/Radio.ino
index 5819129d..541e4cce 100644
--- a/Firmware/LoRaSerial_Firmware/Radio.ino
+++ b/Firmware/LoRaSerial_Firmware/Radio.ino
@@ -889,15 +889,24 @@ bool xmitDatagramP2PSyncClocks()
   memcpy(endOfTxData, &currentMillis, sizeof(currentMillis));
   endOfTxData += sizeof(unsigned long);
 
+  memcpy(endOfTxData, &txHeartbeatUsec, sizeof(txHeartbeatUsec));
+  endOfTxData += sizeof(txHeartbeatUsec);
+
+  memcpy(endOfTxData, &txSyncClockUsec, sizeof(txSyncClockUsec));
+  endOfTxData += sizeof(txSyncClockUsec);
+
+  memcpy(endOfTxData, &txDataAckUsec, sizeof(txDataAckUsec));
+  endOfTxData += sizeof(txDataAckUsec);
+
   /*
-                                                        endOfTxData ---.
-                                                                       |
-                                                                       V
-      +----------+---------+----------+------------+---------+---------+----------+
-      | Optional |         | Optional | Optional   | Channel |         |          |
-      | NET ID   | Control | C-Timer  | SF6 Length | Number  | Millis  | Trailer  |
-      | 8 bits   | 8 bits  | 2 bytes  | 8 bits     | 1 byte  | 4 bytes | n Bytes  |
-      +----------+---------+----------+------------+---------+---------+----------+
+                                                                                                endOfTxData ---.
+                                                                                                               |
+                                                                                                               V
+      +----------+---------+----------+------------+---------+---------+-------------+-------------+-----------+----------+
+      | Optional |         | Optional | Optional   | Channel |         |  HEARTBEAT  | SYNC_CLOCKS | DATA_ACK  |          |
+      | NET ID   | Control | C-Timer  | SF6 Length | Number  | Millis  |    Micros   |    Micros   |   Micros  | Trailer  |
+      | 8 bits   | 8 bits  | 2 bytes  | 8 bits     | 1 byte  | 4 bytes |   4 Bytes   |   4 Bytes   |  4 Bytes  | n Bytes  |
+      +----------+---------+----------+------------+---------+---------+-------------+-------------+-----------+----------+
   */
 
   //Verify the data length

From 2309b2bdb1a4e26f3873fbb24c1993765631f8ed Mon Sep 17 00:00:00 2001
From: Lee Leahy <lpleahyjr@gmail.com>
Date: Mon, 9 Jan 2023 11:19:37 -1000
Subject: [PATCH 25/25] Multipoint: Start the channelTimer synchronization

---
 Firmware/LoRaSerial_Firmware/States.ino | 109 ++++++++++++++++--------
 1 file changed, 72 insertions(+), 37 deletions(-)

diff --git a/Firmware/LoRaSerial_Firmware/States.ino b/Firmware/LoRaSerial_Firmware/States.ino
index c3334279..8a160faf 100644
--- a/Firmware/LoRaSerial_Firmware/States.ino
+++ b/Firmware/LoRaSerial_Firmware/States.ino
@@ -1095,8 +1095,6 @@ void updateRadioState()
     //Start searching for other radios
     //====================
     case RADIO_DISCOVER_BEGIN:
-      stopChannelTimer(); //Stop hopping - multipoint discovery
-
       if (settings.debugSync)
       {
         systemPrintln("Start scanning");
@@ -1114,6 +1112,8 @@ void updateRadioState()
     //Walk through channel table backwards, transmitting a FIND_PARTNER and looking for an SYNC_CLOCKS
     //====================
     case RADIO_DISCOVER_SCANNING:
+      stopChannelTimer(); //Stop hopping - multipoint discovery
+
       if (transactionComplete)
       {
         //Decode the received datagram
@@ -1157,31 +1157,65 @@ void updateRadioState()
             break;
 
           case DATAGRAM_SYNC_CLOCKS:
-            triggerEvent(TRIGGER_RX_SYNC_CLOCKS);
+            if (!settings.server)
+            {
+              //Change to the server's channel number
+              channelNumber = rxVcData[0];
 
-            //Compute the common clock
-            currentMillis = millis();
-            COMPUTE_TIMESTAMP_OFFSET(rxData + 1, 0, txTimeUsec + rxTimeUsec);
+              //Get the HEARTBEAT TX time
+              if (!txHeartbeatUsec)
+              {
+                memcpy(&txHeartbeatUsec, rxData + 1 + 4, sizeof(txHeartbeatUsec));
+                if (settings.debugSync)
+                {
+                  systemPrint("txHeartbeatUsec: ");
+                  systemPrintln(txHeartbeatUsec);
+                }
+              }
 
-            //Server has responded with ACK
-            syncChannelTimer(txRxTimeMsec); //Start and adjust freq hop ISR based on remote's remaining clock
+              //Get the SYNC_CLOCKS TX time
+              if (!txSyncClockUsec)
+              {
+                memcpy(&txSyncClockUsec, rxData + 1 + 4 + 4, sizeof(txSyncClockUsec));
+                if (settings.debugSync)
+                {
+                  systemPrint("txSyncClockUsec: ");
+                  systemPrintln(txSyncClockUsec);
+                }
+              }
 
-            //Change to the server's channel number
-            channelNumber = rxVcData[0];
+              //Ignore this frame when the times are not filled in
+              if ((!txHeartbeatUsec) || (!txSyncClockUsec))
+                triggerEvent(TRIGGER_RX_SYNC_CLOCKS);
+              else
+              {
+                COMPUTE_TIMESTAMP_OFFSET(rxData + 1, 0, txSyncClockUsec);
 
-            if (settings.debugSync)
-            {
-              systemPrint("    Channel Number: ");
-              systemPrintln(channelNumber);
-              outputSerialData(true);
-              if (timeToHop == true) //If the channelTimer has expired, move to next frequency
-                hopChannel();
-            }
+                //Server has responded to FIND_PARTNER with SYNC_CLOCKS
+                //Start and adjust freq hop ISR based on remote's remaining clock
+                startChannelTimer();
+                channelTimerStart -= settings.maxDwellTime;
+                syncChannelTimer((txSyncClockUsec + TX_TO_RX_USEC + micros() - transactionCompleteMicros) / 1000);
+                triggerEvent(TRIGGER_RX_SYNC_CLOCKS);
 
-            frequencyCorrection += radio.getFrequencyError() / 1000000.0;
+                //Switch to the proper frequency for the channel
+                setRadioFrequency(false);
 
-            lastPacketReceived = millis(); //Reset
-            changeState(RADIO_MP_STANDBY);
+                if (settings.debugSync)
+                {
+                  systemPrint("    Channel Number: ");
+                  systemPrintln(channelNumber);
+                  outputSerialData(true);
+                  if (timeToHop == true) //If the channelTimer has expired, move to next frequency
+                    hopChannel();
+                }
+
+                frequencyCorrection += radio.getFrequencyError() / 1000000.0;
+
+                lastPacketReceived = millis(); //Reset
+                changeState(RADIO_MP_STANDBY);
+              }
+            }
             break;
         }
       }
@@ -1319,12 +1353,19 @@ void updateRadioState()
             break;
 
           case DATAGRAM_HEARTBEAT:
-            //Received heartbeat - do not ack.
-            triggerEvent(TRIGGER_RX_HEARTBEAT);
-
             //Sync clock if server sent the heartbeat
             if (settings.server == false)
-              syncChannelTimer(txRxTimeMsec); //Adjust freq hop ISR based on remote's remaining clock
+            {
+              uint16_t frameAirTimeMsec;
+
+              //Adjust freq hop ISR based on server's remaining clock
+              syncChannelTimer((txHeartbeatUsec + TX_TO_RX_USEC + micros() - transactionCompleteMicros) / 1000);
+              systemPrint("HEARTBEAT TX mSec: ");
+              systemPrintln(frameAirTime);
+            }
+
+            //Received heartbeat - do not ack.
+            triggerEvent(TRIGGER_RX_HEARTBEAT);
 
             frequencyCorrection += radio.getFrequencyError() / 1000000.0;
 
@@ -1338,10 +1379,6 @@ void updateRadioState()
             //Received data - do not ack.
             triggerEvent(TRIGGER_RX_DATA);
 
-            //Sync clock if server sent the datagram
-            if (settings.server == false)
-              syncChannelTimer(txRxTimeMsec); //Adjust freq hop ISR based on remote's remaining clock
-
             setHeartbeatMultipoint(); //We're sync'd so reset heartbeat timer
 
             //Place any available data in the serial output buffer
@@ -1362,16 +1399,14 @@ void updateRadioState()
         heartbeatTimeout = ((millis() - heartbeatTimer) > heartbeatRandomTime);
 
         //Only the server transmits heartbeats
-        if (settings.server == true)
+        if ((settings.server == true) && (heartbeatTimeout))
         {
-          if (heartbeatTimeout)
+          if (xmitDatagramMpHeartbeat() == true)
           {
-            if (xmitDatagramMpHeartbeat() == true)
-            {
-              triggerEvent(TRIGGER_TX_HEARTBEAT);
-              setHeartbeatMultipoint(); //We're sending something with clock data so reset heartbeat timer
-              changeState(RADIO_MP_WAIT_TX_DONE); //Wait for heartbeat to transmit
-            }
+            triggerEvent(TRIGGER_TX_HEARTBEAT);
+            blinkHeartbeatLed(true);
+            setHeartbeatMultipoint(); //We're sending something with clock data so reset heartbeat timer
+            changeState(RADIO_MP_WAIT_TX_DONE); //Wait for heartbeat to transmit
           }
         }