update with some improvments:

- check to not fill up the commands stack (and the memory): I can pile up max 100 commands
- try to resync when I get a XOR error message (mostly when the arduino lost its way)
- bugfix my TCO table array
- update schema: my command GPIO is 7, not 38 now

README

@@ -12,7 +12,7 @@ So you need to take HardwareSerial.h and HardwareSerial.cpp and replace these in
 
 Wiring
 ======
-You will need a Max485cpa chip, and pay attention to the wiring image provided. I'm a bit confused on the RJ12 where is the GND and where is the VCC.
+You will need a Max485cpa chip, and pay attention to the wiring image provided. I'm a bit confused on the RJ12 where is the GND and where is the VCC. Also, there is a sense between A and B. If not in the correct position, my program don't decode it properly (I guess bits arrived in the reverse state, i.e. 1 is seen as 0 and 0 is seen as 1). In brief: I don't have code a "auto-reverse".
 
 Code
 ====

arduinoXpressnet/XpressCommand.cpp

@@ -34,7 +34,7 @@ void XpressCommand::writeData(int commandPin,HardwareSerial&serial) {
 
   // wait flush
   delayMicroseconds(220*(_position+1));
-
+   
   digitalWrite(commandPin,LOW);
 
   if (_debug) {
@@ -49,11 +49,16 @@ void XpressCommand::writeData(int commandPin,HardwareSerial&serial) {
 
 
 void XpressCommand::pushStackCommand(XpressCommand *&link, XpressCommand *newCommand) {
+  int count=0;
   if (link==NULL) {
     link=newCommand;
     return;
   }
   while (link->_next!=NULL) {
+    count++;
+    if (count>100) {
+      // drop it, we have too much commands!
+    }
     link=link->_next;
   }
   link->_next=newCommand;

arduinoXpressnet/arduinoXpressnet.ino

@@ -7,7 +7,7 @@
 
 void sendSwitchCommand(int address,int up, int activate);
 /********************* TCO state *******************/
-// pin id, turnout id, isLeftOn1, currentState
+// pin id, turnout id, isLeftOn1 (i.e. reverse the command state), currentState
 int button[][4]={
   {31, 37, LOW, LOW},
   {32, 38, HIGH,LOW},
@@ -31,17 +31,22 @@ void initiateTCOState() {
 
 void checkTCOState() {
   int state;
-  for (int i=0;i<sizeof(button)/(3*sizeof(int));i++) {
+  for (int i=0;i<sizeof(button)/(4*sizeof(int));i++) {
     state=digitalRead(button[i][0]);
     // state changed
     if (state!=button[i][3]) {
+      Serial.print("state (");
+      Serial.print(state);
+      Serial.print(") changed for button");
+      Serial.println(button[i][1]);
       if (state==button[i][2]) {
         sendSwitchCommand(button[i][1],0,1);
         sendSwitchCommand(button[i][1],0,0);
       } else {
         sendSwitchCommand(button[i][1],1,1);
         sendSwitchCommand(button[i][1],1,0);
       }
+      button[i][3]=state;
     }
   }
 }
@@ -51,6 +56,7 @@ void checkTCOState() {
 #define GIO_RXTX 7
 
 // first stage decoding
+#define OPERATION_RESYNC -1
 #define OPERATION_NONE 0
 #define OPERATION_NORMAL_INQUIRY 1
 #define OPERATION_REQUEST_ACKNOWLEDGEbMENT 2
@@ -300,6 +306,19 @@ void poolEvent() {
 int decodeXpressnet(int data) {
   int address;
 
+  // after a XOR problem
+  if (currentOperation==OPERATION_RESYNC) {
+    address=data&0x1f;
+    if ( ! (((data & 0x60) == 0x40) && (address==MYADDRESS))) { // P10AAAAA
+      Serial.print("state=");
+      Serial.print(currentOperation);
+      Serial.print(" data=");
+      Serial.println(data,HEX);
+      return FALSE;
+    }
+    currentOperation=OPERATION_NONE;
+  }
+
   // other xpress device?
   if (data<=255 && currentOperation==OPERATION_NONE) {
     Serial.println();
@@ -372,6 +391,9 @@ int decodeXpressnet(int data) {
     } else { //XOR
       if (xorCheck!=(data&0xff)) {
         Serial.println("incorrect XOR byte");
+        currentOperation=OPERATION_RESYNC;
+        dataPosition=-1;
+        return FALSE;
       }
       //treat
       Serial.print("header=");