First draft of firmware v2.0.0

 - Re-wired for rev.2.0.0 board pinout
 - Added functions for follower/comparator adjustment via PWM
 - Re-tasked resistor ladder to gain factor adjustment
 - Migrated calculations to interger (away from floats)

firmware/AVR-Source/Pyr0_Piezo_Sensor_v2.0.0/Pyr0_Piezo_Sensor_v2.0.0.ino

@@ -0,0 +1,268 @@
+/*
+  Piezoelectric Z-Axis sensor using AtMega88/168/328 (AtMega 48 doesnt have enough memory for this version)
+
+  This sketch reads a piezo element to detect a touch of the printer's nozzle to the bed.
+  The sense pin is tied to an interrupt, which is pulled high by internal pullup resistor.
+  When the piezo touches the bed, the amplification circuit will draw the interrupt pin low
+  and the atmega will output a pulse based on the programmed trigger duration
+  
+ * PD2 INT0 (Piezo In 'D2')
+ * D7 PCINT23 (Trigger OUT 'D7')
+ * PC0 ADC0 (Voltage Reference Check 'A0')
+ * PC1 ADC1 (Sensitivity Adjustment Check 'A1')
+ * PD4 PCINT20 (Error feedback LED 'D4')
+ * PB6 PCINT6 (Voltage Adjustment Resistor 0 'D20')
+ * PB7 PCINT7 (Voltage Adjustment Resistor 1 'D21')
+ * PD5 T1 (Voltage Adjustment Resistor 2 'D5')
+ * PD6 PCINT22 (Voltage Adjustment Resistor 3 'D6')
+ * PB1 OC1A (Comparator VRef PWM Out 'D9')
+ * PD3 OC2B (Voltage Follower VRef PWM Out 'D3')
+
+  Schematics for this project can be found here: https://github.com/pyr0ball/pyr0piezo/tree/master/docs/Schematics
+
+  created 2/18/2019
+  by Alan "pyr0ball" Weinstock
+
+  This code is in the public domain.
+*/
+
+// Set variables for working parameters
+int GAIN_FACTOR = 2;           // Gain adjustment factor. 0=2x, 1=2.5x, 2=3.33x, 3=5x, 4=10x
+int InitCount = 6;             // Number of times to blink the LED on start
+int TRG_DUR = 120;             // duration of the Z-axis pulse sent, in ms
+float senseHighThrs = 2.35;    // Upper threshold of Voltage Follower before adjustment
+float senseLowThrs = 1.8;      // Lower threshold of Voltage Follower before adjustment
+float compHighThrs = 2.75;     // Upper threshold of Comparator before adjustment
+float compLowThrs = 2.54;      // Lower threshold of Comparator before adjustment
+int Vin = 5;                   // input reference voltage
+
+// Analog Pin Assignments
+int V_FOLLOW_PIN = A0;         // Sense pin to check Voltage Follower stage
+int VCOMP_SENSE_PIN = A1;      // Sense pin to check comparator stage voltage
+
+// Digital Pin Assignments
+const int TRG_OUT = 7;         // LED and Z-Min trigger output connected to digital pin 7
+//const int TRG_OUT = 13;      // For testing on Atmega328/2560, Output is moved to onboard LED pin
+//#define Z_TRG 0              // the piezo is connected to INT0 / digital pin 2
+const byte Z_TRG = 2;          // the piezo is connected to INT0 / digital pin 2
+int ERR_LED = 4;               // LED will blink if optimal voltage range cannot be achieved
+const int GADJ_R0 = 20;        // Auto-adjust ladder pin assignments
+const int GADJ_R1 = 21;        // "
+const int GADJ_R2 = 5;         // "
+const int GADJ_R3 = 6;         // "
+int V_FOL_PWM = 3;             // PWM analog output pin for voltage follower adjustment
+int VCOMP_PWM = 9;             // PWM analog output pin for comparator adjustment
+
+// these variables will change on their own. Do not edit ANYTHING below this line
+volatile int sensorHReading = 0;      // variable to store the value read from the sensor pin
+volatile int ADJ_FOLLOW = 0;          // Variable for Follower adjustment
+volatile int ADJ_COMP = 0;            // Variable for Comparator adjustment
+volatile int ERR_STATE = 0;
+
+// Convert float to integer for adjustment functions
+int senseHighInt = (senseHighThrs / 5) * 1024;    // Voltage Follower upper converted to adg interger
+int senseLowInt = (senseLowThrs / 5) * 1024;      // Voltage Follower lower converted to adg interger
+int compHighInt = (compHighThrs / 5) * 1024;      // Upper threshold of Comparator before adjustment
+int compLowInt = (compLowThrs / 5) * 1024;        // Lower threshold of Comparator before adjustment
+
+// Voltage Comparator Adjustment parameters
+float VCompRef = 0.00;                    // variable to store the float value read from the comparator reference
+int VComp = 0;
+int diffCompL = VComp - compLowInt;
+int diffCompH = compHighInt - VComp;
+
+
+// Voltage Follower Adjustment parameters
+float vAdjRead = 0.00;                    // variable to store the value read from the follower
+int VAdj = 0;                    
+int diffAdjL = VAdj - senseLowInt;
+int diffAdjH = senseHighInt - VAdj;
+
+// Error blink parameters
+int BlinkState = LOW;
+int BlinkCount = InitCount * 2;           // Multiply Blink count by 2 to handle toggle state
+
+void setup() {
+  pinMode(TRG_OUT, OUTPUT); // declare the Trigger as as OUTPUT
+  pinMode(ERR_LED, OUTPUT);
+  pinMode(Z_TRG, INPUT_PULLUP); // declare z-sense input with pullup
+  pinMode(V_FOLLOW_PIN, INPUT);
+  pinMode(VCOMP_SENSE_PIN, INPUT);
+  pinMode(GADJ_R0, INPUT); // declare input to break pull to ground
+  pinMode(GADJ_R1, INPUT); // declare input to break pull to ground
+  pinMode(GADJ_R2, INPUT); // declare input to break pull to ground
+  pinMode(GADJ_R3, INPUT); // declare input to break pull to ground
+  Serial.begin(9600);
+
+  // Uncomment the following lines to use PCInt pins instead of hardware interrupt
+  //#include <PinChangeInterrupt.h>
+  //attachPCINT(digitalPinToPCINT(Z_TRG), pulse, FALLING);
+
+  // Uncomment the followoing line to use hardware interrupt pin
+  attachInterrupt(digitalPinToInterrupt(Z_TRG), pulse, FALLING);
+
+  Serial.println("Initializing Piezo Sensor...");
+
+}
+
+/*------------------------------------------------*/
+
+void pulse() {
+  digitalWrite(TRG_OUT, LOW);
+  sensorHReading = 1;
+}
+
+/*------------------------------------------------*/
+
+void adjustFollow() {
+  /* Compares diffs of threshold vs read value
+   if positive, adjusts the follower to within
+   the range set above*/
+  if (diffAdjL > 0.0) {
+    ADJ_FOLLOW + (diffAdjL / 4);
+  }
+  if (diffAdjH > 0.0) {
+    ADJ_FOLLOW - (diffAdjH / 4);
+  }
+
+  // Analog output (PWM) of duty cycle
+  analogWrite(V_FOL_PWM, ADJ_FOLLOW);
+
+  Serial.print("Follower State:");
+  Serial.println(ADJ_FOLLOW);
+  Serial.println("--------------------");
+}
+
+/*------------------------------------------------*/
+
+void adjustComp() {
+  if (diffCompL > 0.0) {
+    ADJ_COMP + (diffCompL / 4);
+  }
+
+  if (diffCompH > 0.0) {
+    ADJ_COMP - (diffCompH / 4);
+  }
+
+  analogWrite(VCOMP_PWM, ADJ_COMP);
+
+  Serial.print("Comparator State:");
+  Serial.println(ADJ_COMP);
+  Serial.println("--------------------");
+}
+
+/*------------------------------------------------*/
+
+void adjustGain() {
+
+  if  (GAIN_FACTOR < 0) {
+    ERR_STATE = 1;
+  }
+  if (GAIN_FACTOR == 0) {
+    pinMode(GADJ_R3, INPUT);
+    pinMode(GADJ_R2, INPUT);
+    pinMode(GADJ_R1, INPUT);
+    pinMode(GADJ_R0, INPUT);
+    ERR_STATE = 0;
+  }
+  if (GAIN_FACTOR > 0) {
+    pinMode(GADJ_R3, OUTPUT);
+    digitalWrite(GADJ_R3, LOW);
+    pinMode(GADJ_R2, INPUT);
+    pinMode(GADJ_R1, INPUT);
+    pinMode(GADJ_R0, INPUT);
+    ERR_STATE = 0;
+  }
+  if (GAIN_FACTOR > 1) {
+    pinMode(GADJ_R2, OUTPUT);
+    digitalWrite(GADJ_R2, LOW);
+    pinMode(GADJ_R1, INPUT);
+    pinMode(GADJ_R0, INPUT);
+    ERR_STATE = 0;
+  }
+  if (GAIN_FACTOR > 2) {
+    pinMode(GADJ_R1, OUTPUT);
+    digitalWrite(GADJ_R1, LOW);
+    pinMode(GADJ_R0, INPUT);
+    ERR_STATE = 0;
+  }
+  if (GAIN_FACTOR > 3) {
+    pinMode(GADJ_R0, OUTPUT);
+    digitalWrite(GADJ_R0, LOW);
+    ERR_STATE = 0;
+  }
+  if  (GAIN_FACTOR > 4) {
+    ERR_STATE = 1;
+  }
+}
+
+/*------------------------------------------------*/
+
+void checkError () {
+  if (ERR_STATE == 1) {
+    digitalWrite(ERR_LED, BlinkState);
+    BlinkState = !BlinkState;
+  }
+  if (ERR_STATE == 0) {
+    BlinkState = LOW;
+    digitalWrite(ERR_LED, BlinkState);
+  }
+}
+
+/*------------------------------------------------*/
+
+void loop() {
+
+  // Blink LED's on init
+  if (BlinkCount > 0) {
+    BlinkState = !BlinkState;
+    digitalWrite(ERR_LED, BlinkState);
+    digitalWrite(TRG_OUT, BlinkState);
+    delay(150);
+    --BlinkCount;
+  }
+
+  // Check voltage of first and second stages and compare against thresholds
+
+  VComp = analogRead(VCOMP_SENSE_PIN);
+  diffCompL = VComp - compLowInt;
+  diffCompH = compHighInt - VComp;
+  VCompRef = (VComp * 5) / 1024;
+
+  VAdj = analogRead(V_FOLLOW_PIN);
+  diffAdjL = VAdj - senseLowInt;
+  diffAdjH = senseHighInt - VAdj;
+  vAdjRead = (VAdj * 5) / 1024;
+
+  // Set the amplification gain factor
+  adjustGain();
+
+  // Voltage Follower adjustment
+  adjustFollow();
+
+  // Voltage Comparator adjustment
+  adjustComp();
+
+  // Check for error state
+  checkError();
+
+  // Checks state of the interrupt trigger, prints status, then sets output pin low
+    Serial.print("PZ Status:");
+    Serial.println(sensorHReading);
+    Serial.print("Voltage Reference:");
+    Serial.println(VCompRef);
+    Serial.print("Amp Sense:");
+    Serial.println(vAdjRead);
+    Serial.print("Comparator State:");
+    Serial.println(ADJ_COMP);
+    Serial.print("Follower State:");
+    Serial.println(ADJ_FOLLOW);
+    Serial.print("Delay:");
+    Serial.println(TRG_DUR);
+    Serial.print("Error State:");
+    Serial.println(ERR_STATE);
+    Serial.println("------------------");
+    delay(TRG_DUR);
+    digitalWrite(TRG_OUT, HIGH);
+    sensorHReading = 0;
+}