Changed how INPUT_PULLUP is done to be compatibile with ESP32

Bumped version to 2.0.6

.gitignore

@@ -0,0 +1,2 @@
+.development
+*.zip

NmraDcc.cpp

@@ -2,11 +2,21 @@
 //
 // Model Railroading with Arduino - NmraDcc.cpp 
 //
-// Copyright (c) 2008 - 2017 Alex Shepherd
+// Copyright (c) 2008 - 2020 Alex Shepherd
 //
-// This source file is subject of the GNU general public license 2,
+// 	This library is free software; you can redistribute it and/or
-// that is available at the world-wide-web at
+// 	modify it under the terms of the GNU Lesser General Public
-// http://www.gnu.org/licenses/gpl.txt
+// 	License as published by the Free Software Foundation; either
+// 	version 2.1 of the License, or (at your option) any later version.
+// 
+// 	This library is distributed in the hope that it will be useful,
+// 	but WITHOUT ANY WARRANTY; without even the implied warranty of
+// 	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// 	Lesser General Public License for more details.
+// 
+// 	You should have received a copy of the GNU Lesser General Public
+// 	License along with this library; if not, write to the Free Software
+// 	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 // 
 //------------------------------------------------------------------------
 //
@@ -25,7 +35,9 @@
 //			  2017-01-19 added STM32F1 support by Franz-Peter
 //            2017-11-29 Ken West (kgw4449@gmail.com):
 //                       Minor fixes to pass NMRA Baseline Conformance Tests.
-//
+//            2018-12-17 added ESP32 support by Trusty (thierry@lapajaparis.net)
+//            2019-02-17 added ESP32 specific changes by Hans Tanner
+//            2020-05-15 changes to pass NMRA Tests ( always search for preamble )
 //------------------------------------------------------------------------
 //
 // purpose:   Provide a simplified interface to decode NMRA DCC packets
@@ -34,12 +46,10 @@
 //------------------------------------------------------------------------
 
 #include "NmraDcc.h"
-#ifdef __AVR_MEGA__
+#include "EEPROM.h"
-#include <avr/eeprom.h>
-#endif
 
 // Uncomment to print DEBUG messages
-//#define DEBUG_PRINT		
+// #define DEBUG_PRINT		
 
 //------------------------------------------------------------------------
 // DCC Receive Routine
@@ -72,26 +82,33 @@
 //           DCC 1: _________XXXXXXXXX_________XXXXXXXXX_________
 //                           |<--------146us------>|
 //                           ^-INTx            ^-INTx
-//                           less than 138us: its a one-Bit
+//                           less than 146us: its a one-Bit
 //                                        
 //
 //                           |<-----------------232us----------->|
 //           DCC 0: _________XXXXXXXXXXXXXXXXXX__________________XXXXXXXX__________
 //                           |<--------146us------->|
 //                           ^-INTx                              ^-INTx
-//                           greater than 138us: its a zero bit
+//                           greater than 146us: its a zero bit
 //                                        
 //                                        
 //                                           
 //           
+
 //------------------------------------------------------------------------
+// if this is commented out, bit synchronisation is only done after a wrong checksum
+#define SYNC_ALWAYS
+
+// if this is commented out, Zero-Bit_Stretching is not supported
+// ( Bits longer than 2* MAX ONEBIT are treated as error )
+#define SUPPORT_ZERO_BIT_STRETCHING
 
 #define MAX_ONEBITFULL  146
 #define MAX_PRAEAMBEL   146 
 #define MAX_ONEBITHALF  82
 #define MIN_ONEBITFULL  82
 #define MIN_ONEBITHALF  35
-#define MAX_BITDIFF     18
+#define MAX_BITDIFF     24
 
 
 // Debug-Ports
@@ -174,9 +191,22 @@
         #define MODE_TP3 pinMode( D7,OUTPUT ) ; // GPIO 13
         #define SET_TP3  GPOS = (1 << D7);
         #define CLR_TP3  GPOC = (1 << D7);
-        #define MODE_TP4 pinMode( D7,OUTPUT ); // GPIO 15
+        #define MODE_TP4 pinMode( D8,OUTPUT ) ; // GPIO 15
-        #define SET_TP4  GPOC = (1 << D8);
+        #define SET_TP4  GPOS = (1 << D8);
         #define CLR_TP4  GPOC = (1 << D8);
+    #elif defined(ESP32)
+        #define MODE_TP1 pinMode( 33,OUTPUT ) ; // GPIO 33
+        #define SET_TP1  GPOS = (1 << 33);
+        #define CLR_TP1  GPOC = (1 << 33);
+        #define MODE_TP2 pinMode( 25,OUTPUT ) ; // GPIO 25
+        #define SET_TP2  GPOS = (1 << 25);
+        #define CLR_TP2  GPOC = (1 << 25);
+        #define MODE_TP3 pinMode( 26,OUTPUT ) ; // GPIO 26
+        #define SET_TP3  GPOS = (1 << 26);
+        #define CLR_TP3  GPOC = (1 << 26);
+        #define MODE_TP4 pinMode( 27,OUTPUT ) ; // GPIO 27
+        #define SET_TP4  GPOS = (1 << 27);
+        #define CLR_TP4  GPOC = (1 << 27);
         
         
     //#elif defined(__AVR_ATmega128__) ||defined(__AVR_ATmega1281__)||defined(__AVR_ATmega2561__)
@@ -202,18 +232,12 @@
     #define MODE_TP2 
     #define SET_TP2 
     #define CLR_TP2 
-        //#define MODE_TP2 DDRC |= (1<<2) // A2
-        //#define SET_TP2 PORTC |= (1<<2)
-        //#define CLR_TP2 PORTC &= ~(1<<2)
     #define MODE_TP3 
     #define SET_TP3 
     #define CLR_TP3 
     #define MODE_TP4 
     #define SET_TP4 
     #define CLR_TP4 
-        //#define MODE_TP4 DDRC |= (1<<4) //A4 
-        //#define SET_TP4 PORTC |= (1<<4) 
-        //#define CLR_TP4 PORTC &= ~(1<<4) 
     
 #endif
 #ifdef DEBUG_PRINT
@@ -230,15 +254,24 @@ struct countOf_t countOf;
 
 #if defined ( __STM32F1__ )
 static ExtIntTriggerMode ISREdge;
+#elif defined ( ESP32 )
+static byte  ISREdge;   // Holder of the Next Edge we're looking for: RISING or FALLING
+static byte  ISRWatch;  // Interrupt Handler Edge Filter 
 #else
-static byte  ISREdge;   // RISING or FALLING
+static byte  ISREdge;   // Holder of the Next Edge we're looking for: RISING or FALLING
+static byte  ISRWatch;  // Interrupt Handler Edge Filter 
 #endif
+byte ISRLevel;          // expected Level at DCC input during ISR ( to detect glitches )
+byte ISRChkMask;       // Flag if Level must be checked
 static word  bitMax, bitMin;
 
 typedef enum
 {
   WAIT_PREAMBLE = 0,
   WAIT_START_BIT,
+  #ifndef SYNC_ALWAYS
+  WAIT_START_BIT_FULL,
+  #endif
   WAIT_DATA,
   WAIT_END_BIT
 } 
@@ -259,6 +292,7 @@ struct DccRx_t
   uint8_t         DataReady ;
   uint8_t         BitCount ;
   uint8_t         TempByte ;
+  uint8_t         chkSum;
   DCC_MSG         PacketBuf;
   DCC_MSG         PacketCopy;
 } 
@@ -275,8 +309,11 @@ typedef struct
   DCC_MSG   LastMsg ;
   uint8_t	ExtIntNum; 
   uint8_t	ExtIntPinNum;
+  volatile uint8_t   *ExtIntPort;     // use port and bitmask to read input at AVR in ISR
+  uint8_t   ExtIntMask;     // digitalRead is too slow on AVR
   int16_t   myDccAddress;	// Cached value of DCC Address from CVs
-  uint8_t   inAccDecDCCAddrNextReceivedMode; 
+  uint8_t   inAccDecDCCAddrNextReceivedMode;
+  uint8_t	cv29Value; 
 #ifdef DCC_DEBUG
   uint8_t	IntCount;
   uint8_t	TickCount;
@@ -287,14 +324,48 @@ DCC_PROCESSOR_STATE ;
 
 DCC_PROCESSOR_STATE DccProcState ;
 
+#ifdef ESP32
+portMUX_TYPE mux = portMUX_INITIALIZER_UNLOCKED;
+
+void IRAM_ATTR ExternalInterruptHandler(void)
+#elif defined(ESP8266)
+void ICACHE_RAM_ATTR ExternalInterruptHandler(void)
+#else
 void ExternalInterruptHandler(void)
+#endif
 {
+    SET_TP3;
+
+#ifdef ESP32
+//   switch (ISRWatch)
+//   {
+//     case RISING: if (digitalRead(DccProcState.ExtIntPinNum)) break; 
+//     case FALLING: if (digitalRead(DccProcState.ExtIntPinNum)) return; break; 
+//   }
+	// First compare the edge we're looking for to the pin state 
+	switch (ISRWatch)
+	{
+		case CHANGE:
+			break;
+				
+		case RISING:
+			if (digitalRead(DccProcState.ExtIntPinNum) != HIGH)
+				return; 
+			break;
+				
+		case FALLING:
+			if (digitalRead(DccProcState.ExtIntPinNum) != LOW)
+				return;
+			break; 
+	}
+#endif
 // Bit evaluation without Timer 0 ------------------------------
     uint8_t DccBitVal;
     static int8_t  bit1, bit2 ;
-    static word  lastMicros;
+    static unsigned int  lastMicros = 0;
-    static byte halfBit, DCC_IrqRunning;
+    static byte halfBit, DCC_IrqRunning, preambleBitCount;
     unsigned int  actMicros, bitMicros;
+    #ifdef ALLOW_NESTED_IRQ
     if ( DCC_IrqRunning ) {
         // nested DCC IRQ - obviously there are glitches
         // ignore this interrupt and increment glitchcounter
@@ -305,57 +376,94 @@ void ExternalInterruptHandler(void)
         SET_TP3;
         return; //>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> abort IRQ
     }
-    SET_TP3;
+    #endif
     actMicros = micros();
     bitMicros = actMicros-lastMicros;
-    if ( bitMicros < bitMin ) {
+
-        // too short - my be false interrupt due to glitch or false protocol -> ignore
+        CLR_TP3; SET_TP3;
+#ifdef __AVR_MEGA__
+    if ( bitMicros < bitMin || ( DccRx.State != WAIT_START_BIT && (*DccProcState.ExtIntPort & DccProcState.ExtIntMask) != (ISRLevel) ) ) {
+#else
+    if ( bitMicros < bitMin || ( DccRx.State != WAIT_START_BIT && digitalRead( DccProcState.ExtIntPinNum ) != (ISRLevel) ) ) {
+#endif
+        // too short - my be false interrupt due to glitch or false protocol  or level does not match RISING / FALLING edge -> ignore this IRQ
         CLR_TP3;
-        SET_TP4; CLR_TP4;
+        SET_TP4; /*delayMicroseconds(1); */ CLR_TP4;
         return; //>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> abort IRQ
     }
-    DccBitVal = ( bitMicros < bitMax );
+        CLR_TP3;  SET_TP3;
+
     lastMicros = actMicros;
-    #ifdef debug
+#ifndef SUPPORT_ZERO_BIT_STRETCHING
-    if(DccBitVal) {SET_TP2;} else {CLR_TP2;};
+    //if ( bitMicros > MAX_ZEROBITFULL ) {
-    #endif
+    if ( bitMicros > (bitMax*2) ) {
+        // too long - my be false protocol -> start over
+        DccRx.State = WAIT_PREAMBLE ;
+        DccRx.BitCount = 0 ;
+        preambleBitCount = 0;
+        // SET_TP2; CLR_TP2;
+        bitMax = MAX_PRAEAMBEL;
+        bitMin = MIN_ONEBITFULL;
+        #if defined ( __STM32F1__ )
+        detachInterrupt( DccProcState.ExtIntNum );
+        #endif
+        #ifdef ESP32
+        ISRWatch = ISREdge;
+        #else
+        attachInterrupt( DccProcState.ExtIntNum, ExternalInterruptHandler, ISREdge );
+        #endif
+        // enable level-checking
+        ISRChkMask = DccProcState.ExtIntMask;
+        ISRLevel = (ISREdge==RISING)? DccProcState.ExtIntMask : 0 ;
+        CLR_TP3;
+        //CLR_TP3;
+        return; //>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> abort IRQ
+    }
+        CLR_TP3;
+        SET_TP3;
+#endif
+    
+    DccBitVal = ( bitMicros < bitMax );
+    
+    #ifdef ALLOW_NESTED_IRQ
     DCC_IrqRunning = true;
     interrupts();  // time critical is only the micros() command,so allow nested irq's
+    #endif
+    
 #ifdef DCC_DEBUG
     DccProcState.TickCount++;
 #endif
-
   switch( DccRx.State )
   {
   case WAIT_PREAMBLE:
-    if( DccBitVal )
+    // We don't have to do anything special - looking for a preamble condition is done always
-    {
+    SET_TP2;
-        SET_TP1;
-      DccRx.BitCount++;
-     if( DccRx.BitCount > 10 ) {
-        DccRx.State = WAIT_START_BIT ;
-        // While waiting for the start bit, detect halfbit lengths. We will detect the correct
-        // sync and detect whether we see a false (e.g. motorola) protocol
-		#if defined ( __STM32F1__ )
-		detachInterrupt( DccProcState.ExtIntNum );
-		#endif
-        attachInterrupt( DccProcState.ExtIntNum, ExternalInterruptHandler, CHANGE);
-        halfBit = 0;
-        bitMax = MAX_ONEBITHALF;
-        bitMin = MIN_ONEBITHALF;
-        CLR_TP1;
-      }
-    } else {
-        SET_TP1;
-        DccRx.BitCount = 0 ;
-        CLR_TP1;
-    }
     break;
 
+#ifndef SYNC_ALWAYS
+  case WAIT_START_BIT_FULL:
+    // wait for startbit without level checking
+    if ( !DccBitVal ) {
+        // we got the startbit
+        CLR_TP2;CLR_TP1;
+        DccRx.State = WAIT_DATA ;
+        CLR_TP1;
+        // initialize packet buffer
+        DccRx.PacketBuf.Size = 0;
+        /*for(uint8_t i = 0; i< MAX_DCC_MESSAGE_LEN; i++ )
+            DccRx.PacketBuf.Data[i] = 0;*/
+        DccRx.PacketBuf.PreambleBits = preambleBitCount;
+        DccRx.BitCount = 0 ;
+        DccRx.chkSum = 0 ;
+        DccRx.TempByte = 0 ;
+        //SET_TP1;
+    }
+    break;
+#endif    
   case WAIT_START_BIT:
     // we are looking for first half "0" bit after preamble
     switch ( halfBit ) {
-      case 0:  //SET_TP1;
+      case 0: 
         // check first part
         if ( DccBitVal ) {
             // is still 1-bit (Preamble)
@@ -363,108 +471,135 @@ void ExternalInterruptHandler(void)
             bit1=bitMicros;
         } else {
             // was "0" half bit, maybe the startbit
-			SET_TP1;
+			halfBit = 4;
-            halfBit = 4;
+		}
-			CLR_TP1;
-        }
         break;
-      case 1: //SET_TP1; // previous halfbit was '1'
+      case 1: // previous halfbit was '1'
         if ( DccBitVal ) {
             // its a '1' halfBit -> we are still in the preamble
             halfBit = 0;
             bit2=bitMicros;
-            DccRx.BitCount++;
+            preambleBitCount++;
             if( abs(bit2-bit1) > MAX_BITDIFF ) {
                 // the length of the 2 halfbits differ too much -> wrong protokoll
-                CLR_TP2;
-                CLR_TP3;
                 DccRx.State = WAIT_PREAMBLE;
                 bitMax = MAX_PRAEAMBEL;
                 bitMin = MIN_ONEBITFULL;
-                DccRx.BitCount = 0;
+                preambleBitCount = 0;
-				SET_TP4;
+                // SET_TP2; CLR_TP2;
-				#if defined ( __STM32F1__ )
+                #if defined ( __STM32F1__ )
 				detachInterrupt( DccProcState.ExtIntNum );
 				#endif
+                #ifdef ESP32
+				ISRWatch = ISREdge;
+                #else
                 attachInterrupt( DccProcState.ExtIntNum, ExternalInterruptHandler, ISREdge );
+                // enable level checking ( with direct port reading @ AVR )
+                ISRChkMask = DccProcState.ExtIntMask;       
+                ISRLevel = (ISREdge==RISING)? DccProcState.ExtIntMask : 0 ;
+                #endif
 				SET_TP3;
-				CLR_TP4;
+                CLR_TP4;
             }
         } else {
             // first '0' half detected in second halfBit
             // wrong sync or not a DCC protokoll
-			CLR_TP3;
+            CLR_TP3;
-            halfBit = 3;
+			halfBit = 3;
-			SET_TP3;
+            SET_TP3;
         }
         break;
-      case 3: //SET_TP1;  // previous halfbit was '0'  in second halfbit  
+      case 3: // previous halfbit was '0'  in second halfbit  
         if ( DccBitVal ) {
             // its a '1' halfbit -> we got only a half '0' bit -> cannot be DCC
             DccRx.State = WAIT_PREAMBLE;
             bitMax = MAX_PRAEAMBEL;
             bitMin = MIN_ONEBITFULL;
-            DccRx.BitCount = 0;
+            preambleBitCount = 0;
+            // SET_TP2; CLR_TP2;
         } else {
             // we got two '0' halfbits -> it's the startbit
             // but sync is NOT ok, change IRQ edge.
+            CLR_TP2;CLR_TP1;
             if ( ISREdge == RISING ) ISREdge = FALLING; else ISREdge = RISING;
             DccRx.State = WAIT_DATA ;
+            CLR_TP1;
             bitMax = MAX_ONEBITFULL;
             bitMin = MIN_ONEBITFULL;
             DccRx.PacketBuf.Size = 0;
-            DccRx.PacketBuf.PreambleBits = 0;
+            /*for(uint8_t i = 0; i< MAX_DCC_MESSAGE_LEN; i++ )
-            for(uint8_t i = 0; i< MAX_DCC_MESSAGE_LEN; i++ )
+            DccRx.PacketBuf.Data[i] = 0;*/
-            DccRx.PacketBuf.Data[i] = 0;
+            DccRx.PacketBuf.PreambleBits = preambleBitCount;
-
-            DccRx.PacketBuf.PreambleBits = DccRx.BitCount;
             DccRx.BitCount = 0 ;
+            DccRx.chkSum = 0 ;
             DccRx.TempByte = 0 ;
+            //SET_TP1;
         }
-		SET_TP4;
+		//SET_TP4;
-			#if defined ( __STM32F1__ )
+
-			detachInterrupt( DccProcState.ExtIntNum );
+        #if defined ( __STM32F1__ )
-			#endif
+        detachInterrupt( DccProcState.ExtIntNum );
-			attachInterrupt( DccProcState.ExtIntNum, ExternalInterruptHandler, ISREdge );
+        #endif
-        CLR_TP1;
+        #ifdef ESP32
-		CLR_TP4;
+        ISRWatch = ISREdge;
+        #else
+        attachInterrupt( DccProcState.ExtIntNum, ExternalInterruptHandler, ISREdge );
+        #endif
+        // enable level-checking
+        ISRChkMask = DccProcState.ExtIntMask;
+        ISRLevel = (ISREdge==RISING)? DccProcState.ExtIntMask : 0 ;
+        //CLR_TP4;
         break;
-      case 4: SET_TP1; // previous (first) halfbit was 0
+      case 4: // previous (first) halfbit was 0
         // if this halfbit is 0 too, we got the startbit
         if ( DccBitVal ) {
             // second halfbit is 1 -> unknown protokoll
             DccRx.State = WAIT_PREAMBLE;
             bitMax = MAX_PRAEAMBEL;
             bitMin = MIN_ONEBITFULL;
+            preambleBitCount = 0;
+            CLR_TP2;CLR_TP1;
             DccRx.BitCount = 0;
         } else {
             // we got the startbit
+            CLR_TP2;CLR_TP1;
             DccRx.State = WAIT_DATA ;
+            CLR_TP1;
             bitMax = MAX_ONEBITFULL;
             bitMin = MIN_ONEBITFULL;
+            // initialize packet buffer
             DccRx.PacketBuf.Size = 0;
-            DccRx.PacketBuf.PreambleBits = 0;
+            /*for(uint8_t i = 0; i< MAX_DCC_MESSAGE_LEN; i++ )
-            for(uint8_t i = 0; i< MAX_DCC_MESSAGE_LEN; i++ )
+            DccRx.PacketBuf.Data[i] = 0;*/
-            DccRx.PacketBuf.Data[i] = 0;
+            DccRx.PacketBuf.PreambleBits = preambleBitCount;
-
-            DccRx.PacketBuf.PreambleBits = DccRx.BitCount;
             DccRx.BitCount = 0 ;
+            DccRx.chkSum = 0 ;
             DccRx.TempByte = 0 ;
+            //SET_TP1;
         }
 		
-        CLR_TP1;
+        //SET_TP4;
-		SET_TP4;
+
 		#if defined ( __STM32F1__ )
 		detachInterrupt( DccProcState.ExtIntNum );
 		#endif
+        #ifdef ESP32
+        ISRWatch = ISREdge;
+        #else
 		attachInterrupt( DccProcState.ExtIntNum, ExternalInterruptHandler, ISREdge );
-		CLR_TP4;
+        #endif
+        // enable level-checking
+        ISRChkMask = DccProcState.ExtIntMask;
+        ISRLevel = (ISREdge==RISING)? DccProcState.ExtIntMask : 0 ;
+
+		//CLR_TP4;
         break;
             
     }        
     break;
 
   case WAIT_DATA:
+    CLR_TP2;
     DccRx.BitCount++;
     DccRx.TempByte = ( DccRx.TempByte << 1 ) ;
     if( DccBitVal )
@@ -483,23 +618,44 @@ void ExternalInterruptHandler(void)
       {
         DccRx.State = WAIT_END_BIT ;
         DccRx.PacketBuf.Data[ DccRx.PacketBuf.Size++ ] = DccRx.TempByte ;
+        DccRx.chkSum ^= DccRx.TempByte;
       }
     }
     break;
 
   case WAIT_END_BIT:
+    SET_TP2;CLR_TP2;
     DccRx.BitCount++;
-    if( DccBitVal ) // End of packet?
+    if( DccBitVal ) { // End of packet?
-    {
+      CLR_TP3; SET_TP4;
-      CLR_TP3;
       DccRx.State = WAIT_PREAMBLE ;
+      DccRx.BitCount = 0 ;
       bitMax = MAX_PRAEAMBEL;
       bitMin = MIN_ONEBITFULL;
-      DccRx.PacketCopy = DccRx.PacketBuf ;
+      SET_TP1;
-      DccRx.DataReady = 1 ;
+      if ( DccRx.chkSum == 0 ) { 
-      SET_TP3;
+        // Packet is valid
-    }
+        #ifdef ESP32
-    else  // Get next Byte
+        portENTER_CRITICAL_ISR(&mux);
+        #endif
+        DccRx.PacketCopy = DccRx.PacketBuf ;
+        DccRx.DataReady = 1 ;
+        #ifdef ESP32
+        portEXIT_CRITICAL_ISR(&mux);
+        #endif
+        // SET_TP2; CLR_TP2;
+        preambleBitCount = 0 ;
+      } else {
+        // Wrong checksum
+        CLR_TP1;
+        #ifdef DCC_DBGVAR
+        DB_PRINT("Cerr");
+        countOf.Err++;
+        #endif
+      }
+
+      SET_TP3; CLR_TP4;
+    } else  { // Get next Byte
       // KGW - Abort immediately if packet is too long.
       if( DccRx.PacketBuf.Size == MAX_DCC_MESSAGE_LEN ) // Packet is too long - abort
       {
@@ -515,38 +671,109 @@ void ExternalInterruptHandler(void)
         DccRx.BitCount = 0 ;
         DccRx.TempByte = 0 ;
       }
+    }
   }
-  CLR_TP1;
+
-  CLR_TP3;
+  // unless we're already looking for the start bit 
+  // we always search for a preamble ( ( 10 or more consecutive 1 bits )
+  // if we found it within a packet, the packet decoding is aborted because
+  // that much one bits cannot be valid in a packet.
+  if ( DccRx.State != WAIT_START_BIT ) {
+    if( DccBitVal )
+    {
+      preambleBitCount++;
+      //SET_TP2;
+      if( preambleBitCount > 10 ) {
+        CLR_TP2;
+#ifndef SYNC_ALWAYS
+        if ( DccRx.chkSum == 0 ) { 
+            // sync must be correct if chksum was ok, no need to check sync
+            DccRx.State = WAIT_START_BIT_FULL;
+        } else {
+#endif
+        DccRx.State = WAIT_START_BIT ;
+            SET_TP2;
+            // While waiting for the start bit, detect halfbit lengths. We will detect the correct
+            // sync and detect whether we see a false (e.g. motorola) protocol
+
+            #if defined ( __STM32F1__ )
+            detachInterrupt( DccProcState.ExtIntNum );
+            #endif
+            #ifdef ESP32
+            ISRWatch = CHANGE;
+            #else
+            attachInterrupt( DccProcState.ExtIntNum, ExternalInterruptHandler, CHANGE);
+            #endif
+            ISRChkMask = 0;         // AVR level check is always true with this settings
+            ISRLevel = 0;           // ( there cannot be false edge IRQ's with CHANGE )
+            halfBit = 0;
+            bitMax = MAX_ONEBITHALF;
+            bitMin = MIN_ONEBITHALF;
+            //CLR_TP1;
+#ifndef SYNC_ALWAYS
+        }
+#endif
+      }
+    } else {
+        CLR_TP1;
+        preambleBitCount = 0 ;
+        // SET_TP2; CLR_TP2;
+    }
+  }
+
+  #ifdef ALLOW_NESTED_IRQ
   DCC_IrqRunning = false;
+  #endif
+  //CLR_TP1;
+  CLR_TP3;
 }
 
 void ackCV(void)
 {
   if( notifyCVAck )
+  {
+    DB_PRINT("ackCV: Send Basic ACK");
     notifyCVAck() ;
+  }
 }
 
-uint8_t readEEPROM( unsigned int CV ) {
+void ackAdvancedCV(void)
+{
+  if( notifyAdvancedCVAck && (DccProcState.cv29Value & CV29_RAILCOM_ENABLE) )
+  {
+    DB_PRINT("ackAdvancedCV: Send RailCom ACK");
+    notifyAdvancedCVAck() ;
+  }
+}
+
+
+uint8_t readEEPROM( unsigned int CV )
+{
     return EEPROM.read(CV) ;
 }
 
-void writeEEPROM( unsigned int CV, uint8_t Value ) {
+void writeEEPROM( unsigned int CV, uint8_t Value )
+{
     EEPROM.write(CV, Value) ;
   #if defined(ESP8266)
     EEPROM.commit();
   #endif
+  #if defined(ESP32)
+    EEPROM.commit();
+  #endif
 }
 
-bool readyEEPROM() {
+bool readyEEPROM()
-    #ifdef __AVR_MEGA__
+{
-        return eeprom_is_ready();
+#if defined ARDUINO_ARCH_MEGAAVR
-    #else
+	return bit_is_clear(NVMCTRL.STATUS,NVMCTRL_EEBUSY_bp);
-        return true;
+#elif defined __AVR_MEGA__
-    #endif
+	return eeprom_is_ready();
+#else
+	return true;
+#endif
 }
 
-
 uint8_t validCV( uint16_t CV, uint8_t Writable )
 {
   if( notifyCVResetFactoryDefault && (CV == CV_MANUFACTURER_ID )  && Writable )
@@ -583,6 +810,9 @@ uint8_t writeCV( unsigned int CV, uint8_t Value)
   {
     case CV_29_CONFIG:
       // copy addressmode Bit to Flags
+      Value = Value &  ~CV29_RAILCOM_ENABLE;   // Bidi (RailCom) Bit must not be enabled, 
+                                            // because you cannot build a Bidi decoder with this lib.
+      DccProcState.cv29Value = Value;
       DccProcState.Flags = ( DccProcState.Flags & ~FLAGS_CV29_BITS) | (Value & FLAGS_CV29_BITS);
       // no break, because myDccAdress must also be reset
     case CV_ACCESSORY_DECODER_ADDRESS_LSB:	// Also same CV for CV_MULTIFUNCTION_PRIMARY_ADDRESS
@@ -611,23 +841,19 @@ uint8_t writeCV( unsigned int CV, uint8_t Value)
 
 uint16_t getMyAddr(void)
 {
-  uint8_t   CV29Value ;
-  
   if( DccProcState.myDccAddress != -1 )	// See if we can return the cached value 
   	return( DccProcState.myDccAddress );
 
-  CV29Value = readCV( CV_29_CONFIG ) ;
+  if( DccProcState.cv29Value & CV29_ACCESSORY_DECODER )  // Accessory Decoder?
-
-  if( CV29Value & CV29_ACCESSORY_DECODER )  // Accessory Decoder?
   {
-    if( CV29Value & CV29_OUTPUT_ADDRESS_MODE ) 
+    if( DccProcState.cv29Value & CV29_OUTPUT_ADDRESS_MODE ) 
       DccProcState.myDccAddress = ( readCV( CV_ACCESSORY_DECODER_ADDRESS_MSB ) << 8 ) | readCV( CV_ACCESSORY_DECODER_ADDRESS_LSB );
     else
       DccProcState.myDccAddress = ( ( readCV( CV_ACCESSORY_DECODER_ADDRESS_MSB ) & 0b00000111) << 6 ) | ( readCV( CV_ACCESSORY_DECODER_ADDRESS_LSB ) & 0b00111111) ;
   }
   else   // Multi-Function Decoder?
   {
-    if( CV29Value & CV29_EXT_ADDRESSING )  // Two Byte Address?
+    if( DccProcState.cv29Value & CV29_EXT_ADDRESSING )  // Two Byte Address?
       DccProcState.myDccAddress = ( ( readCV( CV_MULTIFUNCTION_EXTENDED_ADDRESS_MSB ) - 192 ) << 8 ) | readCV( CV_MULTIFUNCTION_EXTENDED_ADDRESS_LSB ) ;
 
     else
@@ -637,7 +863,7 @@ uint16_t getMyAddr(void)
   return DccProcState.myDccAddress ;
 }
 
-void processDirectOpsOperation( uint8_t Cmd, uint16_t CVAddr, uint8_t Value )
+void processDirectCVOperation( uint8_t Cmd, uint16_t CVAddr, uint8_t Value, void (*ackFunction)() )
 {
   // is it a Byte Operation
   if( Cmd & 0x04 )
@@ -647,8 +873,9 @@ void processDirectOpsOperation( uint8_t Cmd, uint16_t CVAddr, uint8_t Value )
     {
       if( validCV( CVAddr, 1 ) )
       {
+        DB_PRINT("CV: %d Byte Write: %02X", CVAddr, Value)
         if( writeCV( CVAddr, Value ) == Value )
-          ackCV();
+          ackFunction();
       }
     }
 
@@ -656,8 +883,9 @@ void processDirectOpsOperation( uint8_t Cmd, uint16_t CVAddr, uint8_t Value )
     {  
       if( validCV( CVAddr, 0 ) )
       {
+        DB_PRINT("CV: %d Byte Read: %02X", CVAddr, Value)
         if( readCV( CVAddr ) == Value )
-          ackCV();
+          ackFunction();
       }
     }
   }
@@ -670,6 +898,8 @@ void processDirectOpsOperation( uint8_t Cmd, uint16_t CVAddr, uint8_t Value )
 
     uint8_t tempValue = readCV( CVAddr ) ;  // Read the Current CV Value
 
+    DB_PRINT("CV: %d Current Value: %02X  Bit-Wise Mode: %s  Mask: %02X  Value: %02X", CVAddr, tempValue, BitWrite ? "Write":"Read", BitMask, BitValue);
+
     // Perform the Bit Write Operation
     if( BitWrite )
     {
@@ -682,7 +912,7 @@ void processDirectOpsOperation( uint8_t Cmd, uint16_t CVAddr, uint8_t Value )
           tempValue &= ~BitMask ;  // Turn the Bit Off
 
         if( writeCV( CVAddr, tempValue ) == tempValue )
-          ackCV() ;
+          ackFunction() ;
       }
     }
 
@@ -694,12 +924,12 @@ void processDirectOpsOperation( uint8_t Cmd, uint16_t CVAddr, uint8_t Value )
         if( BitValue ) 
         {
           if( tempValue & BitMask )
-            ackCV() ;
+            ackFunction() ;
         }
         else
         {
           if( !( tempValue & BitMask)  )
-            ackCV() ;
+            ackFunction() ;
         }
       }
     }
@@ -742,9 +972,8 @@ void processMultiFunctionMessage( uint16_t Addr, DCC_ADDR_TYPE AddrType, uint8_t
     switch( Cmd & 0b00001110 )
     {
     case 0b00000000:  
-      if( notifyDccReset && ( Cmd & 0b00000001 ) ) // Hard Reset
+      if( notifyDccReset)
-        if( notifyDccReset)
+        notifyDccReset( Cmd & 0b00000001 ) ;
-          notifyDccReset( 1 ) ;
       break ;
 
     case 0b00000010:  // Factory Test
@@ -793,7 +1022,7 @@ void processMultiFunctionMessage( uint16_t Addr, DCC_ADDR_TYPE AddrType, uint8_t
   case 0b01100000:
     //TODO should we cache this info in DCC_PROCESSOR_STATE.Flags ?
 #ifdef NMRA_DCC_ENABLE_14_SPEED_STEP_MODE
-    speedSteps = (readCV( CV_29_CONFIG ) & CV29_F0_LOCATION) ? SPEED_STEP_28 : SPEED_STEP_14 ;
+    speedSteps = (DccProcState.cv29Value & CV29_F0_LOCATION) ? SPEED_STEP_28 : SPEED_STEP_14 ;
 #else
     speedSteps = SPEED_STEP_28 ;
 #endif    
@@ -877,7 +1106,7 @@ void processMultiFunctionMessage( uint16_t Addr, DCC_ADDR_TYPE AddrType, uint8_t
   case 0b11100000:  // CV Access
     CVAddr = ( ( ( Cmd & 0x03 ) << 8 ) | Data1 ) + 1 ;
 
-    processDirectOpsOperation( Cmd, CVAddr, Data2 ) ;
+    processDirectCVOperation( Cmd, CVAddr, Data2, ackAdvancedCV) ;
     break;
   }
 }
@@ -892,7 +1121,7 @@ void processServiceModeOperation( DCC_MSG * pDccMsg )
   if( pDccMsg->Size == 3) // 3 Byte Packets are for Address Only, Register and Paged Mode
   {
     uint8_t RegisterAddr ;
-    DB_PRINT("3-BytePkt");
+    DB_PRINT("CV Address, Register & Paged Mode Operation");
     RegisterAddr = pDccMsg->Data[0] & 0x07 ;
     Value = pDccMsg->Data[1] ;
 
@@ -935,11 +1164,11 @@ void processServiceModeOperation( DCC_MSG * pDccMsg )
 
   else if( pDccMsg->Size == 4) // 4 Byte Packets are for Direct Byte & Bit Mode
   {
-    DB_PRINT("BB-Mode");
+    DB_PRINT("CV Direct Byte and Bit Mode Mode Operation");
     CVAddr = ( ( ( pDccMsg->Data[0] & 0x03 ) << 8 ) | pDccMsg->Data[1] ) + 1 ;
     Value = pDccMsg->Data[2] ;
-
+    
-    processDirectOpsOperation( pDccMsg->Data[0] & 0b00001100, CVAddr, Value ) ;
+    processDirectCVOperation( pDccMsg->Data[0] & 0b00001100, CVAddr, Value, ackCV) ;
   }
 }
 #endif
@@ -1016,12 +1245,13 @@ void execDccProcessor( DCC_MSG * pDccMsg )
     {
       resetServiceModeTimer( 1 ) ;
 
-      if( memcmp( pDccMsg, &DccProcState.LastMsg, sizeof( DCC_MSG ) ) )
+	//Only check the DCC Packet "Size" and "Data" fields and ignore the "PreambleBits" as they can be different to the previous packet
+      if(pDccMsg->Size != DccProcState.LastMsg.Size || memcmp( pDccMsg->Data, &DccProcState.LastMsg.Data, pDccMsg->Size ) != 0 )	      
       {
         DccProcState.DuplicateCount = 0 ;
         memcpy( &DccProcState.LastMsg, pDccMsg, sizeof( DCC_MSG ) ) ;
       }
-      // Wait until you see 2 identicle packets before acting on a Service Mode Packet 
+      // Wait until you see 2 identical packets before acting on a Service Mode Packet 
       else
       {
         DccProcState.DuplicateCount++ ;
@@ -1277,14 +1507,30 @@ void NmraDcc::pin( uint8_t ExtIntNum, uint8_t ExtIntPinNum, uint8_t EnablePullup
 #if defined ( __STM32F1__ )
   // with STM32F1 the interuptnumber is equal the pin number
   DccProcState.ExtIntNum = ExtIntPinNum;
+  // because STM32F1 has a NVIC we must set interuptpriorities
+  const nvic_irq_num irqNum2nvic[] = { NVIC_EXTI0, NVIC_EXTI1, NVIC_EXTI2, NVIC_EXTI3, NVIC_EXTI4, 
+            NVIC_EXTI_9_5, NVIC_EXTI_9_5, NVIC_EXTI_9_5, NVIC_EXTI_9_5, NVIC_EXTI_9_5, 
+            NVIC_EXTI_15_10, NVIC_EXTI_15_10, NVIC_EXTI_15_10, NVIC_EXTI_15_10, NVIC_EXTI_15_10, NVIC_EXTI_15_10 };
+  exti_num irqNum =  (exti_num)(PIN_MAP[ExtIntPinNum].gpio_bit); 
+
+// DCC-Input IRQ must be able to interrupt other long low priority ( level15 ) IRQ's  
+  nvic_irq_set_priority ( irqNum2nvic[irqNum], PRIO_DCC_IRQ); 
+  
+// Systic must be able to interrupt DCC-IRQ to always get correct micros() values  
+  nvic_irq_set_priority(NVIC_SYSTICK, PRIO_SYSTIC); 
 #else
   DccProcState.ExtIntNum = ExtIntNum;
 #endif
   DccProcState.ExtIntPinNum = ExtIntPinNum;
-	
+#ifdef __AVR_MEGA__
-  pinMode( ExtIntPinNum, INPUT );
+    // because digitalRead at AVR is slow, we will read the dcc input in the ISR
-  if( EnablePullup )
+    // by direct port access.
-    digitalWrite(ExtIntPinNum, HIGH);
+    DccProcState.ExtIntPort = portInputRegister( digitalPinToPort(ExtIntPinNum) );
+    DccProcState.ExtIntMask = digitalPinToBitMask( ExtIntPinNum );
+#else
+    DccProcState.ExtIntMask = 1;
+#endif	
+  pinMode( ExtIntPinNum, EnablePullup ? INPUT_PULLUP : INPUT );
 }
 
 ////////////////////////////////////////////////////////////////////////
@@ -1299,6 +1545,9 @@ void NmraDcc::init( uint8_t ManufacturerId, uint8_t VersionId, uint8_t Flags, ui
   #if defined(ESP8266)
     EEPROM.begin(MAXCV);
   #endif
+  #if defined(ESP32)
+    EEPROM.begin(MAXCV);
+  #endif
   // Clear all the static member variables
   memset( &DccRx, 0, sizeof( DccRx) );
 
@@ -1306,20 +1555,30 @@ void NmraDcc::init( uint8_t ManufacturerId, uint8_t VersionId, uint8_t Flags, ui
   MODE_TP2;
   MODE_TP3;
   MODE_TP4;
-  ISREdge = RISING;
   bitMax = MAX_ONEBITFULL;
   bitMin = MIN_ONEBITFULL;
-  attachInterrupt( DccProcState.ExtIntNum, ExternalInterruptHandler, RISING);
 
   DccProcState.Flags = Flags ;
   DccProcState.OpsModeAddressBaseCV = OpsModeAddressBaseCV ;
   DccProcState.myDccAddress = -1;
   DccProcState.inAccDecDCCAddrNextReceivedMode = 0;
 
+  ISREdge = RISING;
+  // level checking to detect false IRQ's fired by glitches
+  ISRLevel = DccProcState.ExtIntMask;
+  ISRChkMask = DccProcState.ExtIntMask;
+
+  #ifdef ESP32
+  ISRWatch = ISREdge;
+  attachInterrupt( DccProcState.ExtIntNum, ExternalInterruptHandler, CHANGE);
+  #else
+  attachInterrupt( DccProcState.ExtIntNum, ExternalInterruptHandler, RISING);
+  #endif
+
   // Set the Bits that control Multifunction or Accessory behaviour
   // and if the Accessory decoder optionally handles Output Addressing 
   // we need to peal off the top two bits
-  writeCV( CV_29_CONFIG, ( readCV( CV_29_CONFIG ) & ~FLAGS_CV29_BITS ) | (Flags & FLAGS_CV29_BITS) ) ; 
+  DccProcState.cv29Value = writeCV( CV_29_CONFIG, ( readCV( CV_29_CONFIG ) & ~FLAGS_CV29_BITS ) | (Flags & FLAGS_CV29_BITS) ) ; 
 
   uint8_t doAutoFactoryDefault = 0;
   if((Flags & FLAGS_AUTO_FACTORY_DEFAULT) && (readCV(CV_VERSION_ID) == 255) && (readCV(CV_MANUFACTURER_ID) == 255))
@@ -1418,30 +1677,29 @@ uint8_t NmraDcc::process()
   if( DccRx.DataReady )
   {
     // We need to do this check with interrupts disabled
-    //SET_TP4;
+#ifdef ESP32
+    portENTER_CRITICAL(&mux);
+#else
     noInterrupts();
+#endif
     Msg = DccRx.PacketCopy ;
     DccRx.DataReady = 0 ;
+
+#ifdef ESP32
+    portEXIT_CRITICAL(&mux);
+#else
     interrupts();
-      #ifdef DCC_DBGVAR
+#endif
-      countOf.Tel++;
+    // Checking of the XOR-byte is now done in the ISR already
-      #endif
+    #ifdef DCC_DBGVAR
+    countOf.Tel++;
+    #endif
+    // Clear trailing bytes
+    for ( byte i=Msg.Size; i< MAX_DCC_MESSAGE_LEN; i++ ) Msg.Data[i] = 0;
     
-    uint8_t xorValue = 0 ;
+	if( notifyDccMsg ) 	notifyDccMsg( &Msg );
-    
-    for(uint8_t i = 0; i < DccRx.PacketCopy.Size; i++)
-      xorValue ^= DccRx.PacketCopy.Data[i];
-    if(xorValue) {
-      #ifdef DCC_DBGVAR
-      DB_PRINT("Cerr");
-      countOf.Err++;
-      #endif
-      return 0 ;
-    } else {
-		if( notifyDccMsg ) 	notifyDccMsg( &Msg );
 		
-        execDccProcessor( &Msg );
+     execDccProcessor( &Msg );
-    }
     return 1 ;
   }
 

NmraDcc.h

@@ -2,11 +2,21 @@
 //
 // Model Railroading with Arduino - NmraDcc.h 
 //
-// Copyright (c) 2008 - 2018 Alex Shepherd
+// Copyright (c) 2008 - 2020 Alex Shepherd
 //
-// This source file is subject of the GNU general public license 2,
+// 	This library is free software; you can redistribute it and/or
-// that is available at the world-wide-web at
+// 	modify it under the terms of the GNU Lesser General Public
-// http://www.gnu.org/licenses/gpl.txt
+// 	License as published by the Free Software Foundation; either
+// 	version 2.1 of the License, or (at your option) any later version.
+// 
+// 	This library is distributed in the hope that it will be useful,
+// 	but WITHOUT ANY WARRANTY; without even the implied warranty of
+// 	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// 	Lesser General Public License for more details.
+// 
+// 	You should have received a copy of the GNU Lesser General Public
+// 	License along with this library; if not, write to the Free Software
+// 	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 // 
 //------------------------------------------------------------------------
 //
@@ -32,7 +42,7 @@
 // Uncomment the following Line to Enable Service Mode CV Programming
 #define NMRA_DCC_PROCESS_SERVICEMODE
 
-// Uncomment the following line to Enable MutliFunction Decoder Operations
+// Uncomment the following line to Enable MultiFunction Decoder Operations
 #define NMRA_DCC_PROCESS_MULTIFUNCTION
 
 // Uncomment the following line to Enable 14 Speed Step Support
@@ -44,15 +54,15 @@
 #include "WProgram.h"
 #endif
 
-#include "EEPROM.h"
-
 #ifndef NMRADCC_IS_IN
 #define NMRADCC_IS_IN
 
-#define NMRADCC_VERSION     200     // Version 2.0.0
+#define NMRADCC_VERSION     206     // Version 2.0.6
 
 #define MAX_DCC_MESSAGE_LEN 6    // including XOR-Byte
 
+//#define ALLOW_NESTED_IRQ      // uncomment to enable nested IRQ's ( only for AVR! )
+
 typedef struct
 {
 	uint8_t	Size ;
@@ -96,21 +106,27 @@ typedef struct
 #define CV_MANUFACTURER_ID                     8
 #define CV_29_CONFIG                          29
 
-#if defined(ESP8266)
+#if defined(ESP32)
-#include <spi_flash.h>
+	#include <esp_spi_flash.h>
-#define MAXCV     SPI_FLASH_SEC_SIZE
+	#define MAXCV     SPI_FLASH_SEC_SIZE
+#elif defined(ESP8266)
+	#include <spi_flash.h>
+	#define MAXCV     SPI_FLASH_SEC_SIZE
 #elif defined( __STM32F1__)
-#define MAXCV	(EEPROM_PAGE_SIZE/4 - 1)	// number of storage places (CV address could be larger
+	#define MAXCV	(EEPROM_PAGE_SIZE/4 - 1)	// number of storage places (CV address could be larger
 											// because STM32 uses virtual adresses)
+    #undef ALLOW_NESTED_IRQ                 // This is done with NVIC on STM32
+    #define PRIO_DCC_IRQ    9
+    #define PRIO_SYSTIC     8               // MUST be higher priority than DCC Irq
 #else
-#define MAXCV    E2END     					// the upper limit of the CV value currently defined to max memory.
+	#define MAXCV    E2END     					// the upper limit of the CV value currently defined to max memory.
 #endif
 
 typedef enum {
     CV29_LOCO_DIR            = 0b00000001,	/** bit 0: Locomotive Direction: "0" = normal, "1" = reversed */
     CV29_F0_LOCATION         = 0b00000010,	/** bit 1: F0 location: "0" = bit 4 in Speed and Direction instructions, "1" = bit 4 in function group one instruction */
     CV29_APS                 = 0b00000100,	/** bit 2: Alternate Power Source (APS) "0" = NMRA Digital only, "1" = Alternate power source set by CV12 */
-    CV29_ADV_ACK             = 0b00001000, 	/** bit 3: ACK, Advanced Acknowledge mode enabled if 1, disabled if 0 */
+	CV29_RAILCOM_ENABLE      = 0b00001000, 	/** bit 3: BiDi ( RailCom ) is active */
     CV29_SPEED_TABLE_ENABLE  = 0b00010000, 	/** bit 4: STE, Speed Table Enable, "0" = values in CVs 2, 4 and 6, "1" = Custom table selected by CV 25 */
     CV29_EXT_ADDRESSING      = 0b00100000,	/** bit 5: "0" = one byte addressing, "1" = two byte addressing */
     CV29_OUTPUT_ADDRESS_MODE = 0b01000000,	/** bit 6: "0" = Decoder Address Mode "1" = Output Address Mode */
@@ -651,7 +667,7 @@ extern uint8_t notifyIsSetCVReady(void) __attribute__ ((weak));
  *  notifyCVChange()  Called when a CV value is changed.
  *                    This is called whenever a CV's value is changed.
  *  notifyDccCVChange()  Called only when a CV value is changed by a Dcc packet or a internal lib function.
- *                    it is NOT called if the CV is chaged by means of the setCV() method.
+ *                    it is NOT called if the CV is changed by means of the setCV() method.
  *                    Note: It is not called if notifyCVWrite() is defined
  *                    or if the value in the EEPROM is the same as the value
  *                    in the write command. 
@@ -695,6 +711,17 @@ extern void    notifyCVResetFactoryDefault(void) __attribute__ ((weak));
  *    None
  */
 extern void    notifyCVAck(void) __attribute__ ((weak));
+/*+
+ *  notifyAdvancedCVAck() Called when a CV write must be acknowledged via Advanced Acknowledgement.
+ *                This callback must send the Advanced Acknowledgement via RailComm.
+ *
+ *  Inputs:
+ *    None
+ *                                                                                                        *
+ *  Returns:
+ *    None
+ */
+extern void    notifyAdvancedCVAck(void) __attribute__ ((weak));
 /*+
  *  notifyServiceMode(bool) Called when state of 'inServiceMode' changes
  *

examples/DCCInterface_TurntableControl/DCCInterface_TurntableControl.ino

@@ -1,8 +1,8 @@
 // DCC Stepper Motor Controller ( A4988 ) Example for Model Railroad Turntable Control
 //
-// See: https://www.dccinterface.com/how-to/assemblyguide/
+// See: https://www.dccinterface.com/product/arduino-model-railway-dcc-stepper-motor-controller-a4988-assembled/
 // 
-// Author: Alex Shepherd 2017-12-04
+// Author: Alex Shepherd 2020-06-01
 // 
 // This example requires two Arduino Libraries:
 //
@@ -22,12 +22,22 @@
 // The lines below define the pins used to connect to the A4988 driver module
 #define A4988_STEP_PIN      4
 #define A4988_DIRECTION_PIN 5
-// Uncomment the next line to enable Powering-Off the Stepper when its not running to reduce heating the motor and driver
 #define A4988_ENABLE_PIN    6
 
+#ifdef A4988_ENABLE_PIN
+// Uncomment the next line to enable Powering-Off the Stepper when its not running to reduce heating the motor and driver
+#define DISABLE_OUTPUTS_IDLE
+#endif
+
+// By default the stepper motor will move the shortest distance to the desired position.
+// If you need the turntable to only move in the Positive/Increasing or Negative/Decreasing step numbers to better handle backlash in the mechanism
+// Then uncomment the appropriate line below
+//#define ALWAYS_MOVE_POSITIVE
+//#define ALWAYS_MOVE_NEGATIVE
+
 // The lines below define the stepping speed and acceleration, which you may need to tune for your application
 #define STEPPER_MAX_SPEED     800   // Sets the maximum permitted speed
-#define STEPPER_ACCELARATION  1000   // Sets the acceleration/deceleration rate
+#define STEPPER_ACCELARATION  1000  // Sets the acceleration/deceleration rate
 #define STEPPER_SPEED         300   // Sets the desired constant speed for use with runSpeed()
 
 // The line below defines the number of "Full Steps" your stepper motor does for a full rotation
@@ -92,6 +102,9 @@ TurnoutPosition turnoutPositions[] = {
 // --------------------------------------------------------------------------------------------
 // You shouldn't need to edit anything below this line unless you're needing to make big changes... ;)
 // --------------------------------------------------------------------------------------------
+#if defined(ALWAYS_MOVE_POSITIVE) && defined(ALWAYS_MOVE_NEGATIVE)
+#error ONLY uncomment one of ALWAYS_MOVE_POSITIVE or ALWAYS_MOVE_NEGATIVE but NOT both
+#endif
 
 #define MAX_TURNOUT_POSITIONS (sizeof(turnoutPositions) / sizeof(TurnoutPosition))
 
@@ -104,11 +117,12 @@ NmraDcc  Dcc ;
 // Variables to store the last DCC Turnout message Address and Direction  
 uint16_t lastAddr = 0xFFFF ;
 uint8_t lastDirection = 0xFF;
+int     lastStep = 0;
 
 // This function is called whenever a normal DCC Turnout Packet is received
 void notifyDccAccTurnoutOutput( uint16_t Addr, uint8_t Direction, uint8_t OutputPower )
 {
-  Serial.print("notifyDccAccTurnoutOutput: ") ;
+  Serial.print(F("notifyDccAccTurnoutOutput: "));
   Serial.print(Addr,DEC) ;
   Serial.print(',');
   Serial.print(Direction,DEC) ;
@@ -131,23 +145,50 @@ void notifyDccAccTurnoutOutput( uint16_t Addr, uint8_t Direction, uint8_t Output
 #ifdef A4988_ENABLE_PIN
       stepper1.enableOutputs();
 #endif
-      if (Direction)
+
-      {
+      int newStep;
-        Serial.println(turnoutPositions[i].positionFront, DEC);
+      if(Direction)
-        stepper1.moveTo(turnoutPositions[i].positionFront);
+        newStep = turnoutPositions[i].positionFront;
-        break;
-      }
       else
-      {
+        newStep = turnoutPositions[i].positionBack;
-        Serial.println(turnoutPositions[i].positionBack, DEC);
+
-        stepper1.moveTo(turnoutPositions[i].positionBack);
+      Serial.print(newStep, DEC);
-        break;
+      
-      }
+      Serial.print(F("  Last Step: "));
+      Serial.print(lastStep, DEC);
+      
+      int diffStep = newStep - lastStep;
+      Serial.print(F("  Diff Step: "));
+      Serial.print(diffStep, DEC);
+
+#if defined ALWAYS_MOVE_POSITIVE
+      Serial.print(F("  Positive"));       
+      if(diffStep < 0)
+        diffStep += FULL_TURN_STEPS;
+        
+#elif defined ALWAYS_MOVE_NEGATIVE
+      Serial.print(F("  Negative"));       
+      if(diffStep > 0)
+        diffStep -= FULL_TURN_STEPS;
+#else
+      if(diffStep > HALF_TURN_STEPS)
+        diffStep = diffStep - FULL_TURN_STEPS;
+        
+      else if(diffStep < -HALF_TURN_STEPS)
+        diffStep = diffStep + FULL_TURN_STEPS;
+#endif
+
+      Serial.print(F("  Move: "));
+      Serial.println(diffStep, DEC);
+      stepper1.move(diffStep);
+
+      lastStep = newStep;
+      break;
     }
   }
 };
 
-#ifdef A4988_ENABLE_PIN
+#ifdef DISABLE_OUTPUTS_IDLE
 bool lastIsRunningState ;
 #endif 
 
@@ -161,8 +202,12 @@ void setupStepperDriver()
   stepper1.setMaxSpeed(STEPPER_MAX_SPEED);        // Sets the maximum permitted speed
   stepper1.setAcceleration(STEPPER_ACCELARATION); // Sets the acceleration/deceleration rate
   stepper1.setSpeed(STEPPER_SPEED);               // Sets the desired constant speed for use with runSpeed()
- 
+
 #ifdef A4988_ENABLE_PIN
+  stepper1.enableOutputs();
+#endif
+
+#ifdef DISABLE_OUTPUTS_IDLE
   lastIsRunningState = stepper1.isRunning();
 #endif
 }
@@ -173,14 +218,19 @@ bool moveToHomePosition()
 
   pinMode(HOME_SENSOR_PIN, INPUT_PULLUP);
 
+#ifdef ALWAYS_MOVE_NEGATIVE
+  stepper1.move(0 - (FULL_TURN_STEPS * 2));
+#else
   stepper1.move(FULL_TURN_STEPS * 2);
+#endif  
   while(digitalRead(HOME_SENSOR_PIN) != HOME_SENSOR_ACTIVE_STATE)
     stepper1.run();
 
   if(digitalRead(HOME_SENSOR_PIN) == HOME_SENSOR_ACTIVE_STATE)
   {
-    Serial.println(F("Found Home Position - Setting Current Position to 0"));
+    stepper1.stop();
     stepper1.setCurrentPosition(0);
+    Serial.println(F("Found Home Position - Setting Current Position to 0"));
     return true;
   }
   else
@@ -210,28 +260,32 @@ void setup()
   Serial.print(F("Full Rotation Steps: "));
   Serial.println(FULL_TURN_STEPS);
 
+  Serial.print(F("Movement Strategy: "));
+#if defined ALWAYS_MOVE_POSITIVE
+  Serial.println(F("Positive Direction Only"));
+#elif defined ALWAYS_MOVE_NEGATIVE
+  Serial.println(F("Negative Direction Only"));
+#else
+  Serial.println(F("Shortest Distance"));
+#endif
+
   for(uint8_t i = 0; i < MAX_TURNOUT_POSITIONS; i++)
   {
-    Serial.print("DCC Addr: ");
+    Serial.print(F("DCC Addr: "));
     Serial.print(turnoutPositions[i].dccAddress);
 
-    Serial.print(" Front: ");
+    Serial.print(F(" Front: "));
     Serial.print(turnoutPositions[i].positionFront);
 
-    Serial.print(" Back: ");
+    Serial.print(F(" Back: "));
     Serial.println(turnoutPositions[i].positionBack);
   }
   
   setupStepperDriver();
-
   if(moveToHomePosition());
   { 
     setupDCCDecoder();
 
-  #ifdef A4988_ENABLE_PIN
-    stepper1.enableOutputs();
-  #endif
-
     // Fake a DCC Packet to cause the Turntable to move to Position 1
     notifyDccAccTurnoutOutput(POSITION_01_DCC_ADDRESS, 1, 1);
   }
@@ -245,7 +299,7 @@ void loop()
   // Process the Stepper Library
   stepper1.run();
 
-#ifdef A4988_ENABLE_PIN
+#ifdef DISABLE_OUTPUTS_IDLE
   if(stepper1.isRunning() != lastIsRunningState)
   {
     lastIsRunningState = stepper1.isRunning();

examples/NmraDccMultiFunctionMotorDecoder/NmraDccMultiFunctionMotorDecoder.ino

@@ -0,0 +1,314 @@
+// NMRA Dcc Multifunction Motor Decoder Demo
+//
+// Author: Alex Shepherd 2019-03-30
+// 
+// This example requires these Arduino Libraries:
+//
+// 1) The NmraDcc Library from: http://mrrwa.org/download/
+//
+// These libraries can be found and installed via the Arduino IDE Library Manager
+//
+// This is a simple demo of how to drive and motor speed and direction using PWM and a motor H-Bridge
+// It uses vStart and vHigh CV values to customise the PWM values to the motor response 
+// It also uses the Headling Function to drive 2 LEDs for Directional Headlights
+// Apart from that there's nothing fancy like Lighting Effects or a function matrix or Speed Tables - its just the basics...
+//
+
+#include <NmraDcc.h>
+// Uncomment any of the lines below to enable debug messages for different parts of the code
+//#define DEBUG_FUNCTIONS
+//#define DEBUG_SPEED
+//#define DEBUG_PWM
+//#define DEBUG_DCC_ACK
+//#define DEBUG_DCC_MSG
+
+#if defined(DEBUG_FUNCTIONS) or defined(DEBUG_SPEED) or defined(DEBUG_PWM) or defined(DEBUG_DCC_ACK) or defined(DEBUG_DCC_MSG)
+#define DEBUG_PRINT
+#endif
+
+// This is the default DCC Address
+#define DEFAULT_DECODER_ADDRESS 3
+
+// This section defines the Arduino UNO Pins to use 
+#ifdef __AVR_ATmega328P__ 
+
+#define DCC_PIN     2
+
+#define LED_PIN_FWD 5
+#define LED_PIN_REV 6
+#define MOTOR_DIR_PIN 12
+#define MOTOR_PWM_PIN 3
+
+// This section defines the Arduino ATTiny85 Pins to use 
+#elif ARDUINO_AVR_ATTINYX5 
+
+#define DCC_PIN     2
+
+#define LED_PIN_FWD 0
+#define LED_PIN_REV 1
+#define MOTOR_DIR_PIN 3
+#define MOTOR_PWM_PIN 4
+
+#else
+#error "Unsupported CPU, you need to add another configuration section for your CPU"
+#endif 
+
+// Some global state variables
+uint8_t newLedState = 0;
+uint8_t lastLedState = 0;
+
+uint8_t newDirection = 0;
+uint8_t lastDirection = 0;
+
+uint8_t newSpeed = 0;
+uint8_t lastSpeed = 0;
+uint8_t numSpeedSteps = SPEED_STEP_128;
+
+uint8_t vStart;
+uint8_t vHigh;
+
+// Structure for CV Values Table
+struct CVPair
+{
+  uint16_t  CV;
+  uint8_t   Value;
+};
+
+// CV Addresses we will be using
+#define CV_VSTART  2
+#define CV_VHIGH   5
+
+// Default CV Values Table
+CVPair FactoryDefaultCVs [] =
+{
+	// The CV Below defines the Short DCC Address
+  {CV_MULTIFUNCTION_PRIMARY_ADDRESS, DEFAULT_DECODER_ADDRESS},
+
+  // Three Step Speed Table
+  {CV_VSTART, 120},
+  {CV_VHIGH, 255},
+
+  // These two CVs define the Long DCC Address
+  {CV_MULTIFUNCTION_EXTENDED_ADDRESS_MSB, 0},
+  {CV_MULTIFUNCTION_EXTENDED_ADDRESS_LSB, DEFAULT_DECODER_ADDRESS},
+
+// ONLY uncomment 1 CV_29_CONFIG line below as approprate
+//  {CV_29_CONFIG,                                      0}, // Short Address 14 Speed Steps
+  {CV_29_CONFIG,                       CV29_F0_LOCATION}, // Short Address 28/128 Speed Steps
+//  {CV_29_CONFIG, CV29_EXT_ADDRESSING | CV29_F0_LOCATION}, // Long  Address 28/128 Speed Steps  
+};
+
+NmraDcc  Dcc ;
+
+uint8_t FactoryDefaultCVIndex = 0;
+
+// This call-back function is called when a CV Value changes so we can update CVs we're using
+void notifyCVChange( uint16_t CV, uint8_t Value)
+{
+  switch(CV)
+  {
+    case CV_VSTART:
+      vStart = Value;
+      break;
+      
+    case CV_VHIGH:
+      vHigh = Value;
+      break;
+  }
+}
+
+void notifyCVResetFactoryDefault()
+{
+  // Make FactoryDefaultCVIndex non-zero and equal to num CV's to be reset 
+  // to flag to the loop() function that a reset to Factory Defaults needs to be done
+  FactoryDefaultCVIndex = sizeof(FactoryDefaultCVs)/sizeof(CVPair);
+};
+
+// This call-back function is called whenever we receive a DCC Speed packet for our address 
+void notifyDccSpeed( uint16_t Addr, DCC_ADDR_TYPE AddrType, uint8_t Speed, DCC_DIRECTION Dir, DCC_SPEED_STEPS SpeedSteps )
+{
+  #ifdef DEBUG_SPEED
+  Serial.print("notifyDccSpeed: Addr: ");
+  Serial.print(Addr,DEC);
+  Serial.print( (AddrType == DCC_ADDR_SHORT) ? "-S" : "-L" );
+  Serial.print(" Speed: ");
+  Serial.print(Speed,DEC);
+  Serial.print(" Steps: ");
+  Serial.print(SpeedSteps,DEC);
+  Serial.print(" Dir: ");
+  Serial.println( (Dir == DCC_DIR_FWD) ? "Forward" : "Reverse" );
+  #endif
+
+  newDirection = Dir;
+  newSpeed = Speed;
+  numSpeedSteps = SpeedSteps;
+};
+
+// This call-back function is called whenever we receive a DCC Function packet for our address 
+void notifyDccFunc(uint16_t Addr, DCC_ADDR_TYPE AddrType, FN_GROUP FuncGrp, uint8_t FuncState)
+{
+  #ifdef DEBUG_FUNCTIONS
+  Serial.print("notifyDccFunc: Addr: ");
+  Serial.print(Addr,DEC);
+  Serial.print( (AddrType == DCC_ADDR_SHORT) ? 'S' : 'L' );
+  Serial.print("  Function Group: ");
+  Serial.print(FuncGrp,DEC);
+  #endif
+
+  if(FuncGrp == FN_0_4)
+  {
+    newLedState = (FuncState & FN_BIT_00) ? 1 : 0;
+    #ifdef DEBUG_FUNCTIONS
+    Serial.print(" FN 0: ");
+    Serial.print(newLedState);
+    #endif
+  }
+  #ifdef DEBUG_FUNCTIONS
+  Serial.println();
+  #endif
+}
+
+// This call-back function is called whenever we receive a DCC Packet
+#ifdef  DEBUG_DCC_MSG
+void notifyDccMsg( DCC_MSG * Msg)
+{
+  Serial.print("notifyDccMsg: ") ;
+  for(uint8_t i = 0; i < Msg->Size; i++)
+  {
+    Serial.print(Msg->Data[i], HEX);
+    Serial.write(' ');
+  }
+  Serial.println();
+}
+#endif
+
+// This call-back function is called by the NmraDcc library when a DCC ACK needs to be sent
+// Calling this function should cause an increased 60ma current drain on the power supply for 6ms to ACK a CV Read
+// So we will just turn the motor on for 8ms and then turn it off again.
+
+void notifyCVAck(void)
+{
+  #ifdef DEBUG_DCC_ACK
+  Serial.println("notifyCVAck") ;
+  #endif
+
+  digitalWrite(MOTOR_DIR_PIN, HIGH);
+  digitalWrite(MOTOR_PWM_PIN, HIGH);
+
+  delay( 8 );  
+
+  digitalWrite(MOTOR_DIR_PIN, LOW);
+  digitalWrite(MOTOR_PWM_PIN, LOW);
+}
+
+void setup()
+{
+  #ifdef DEBUG_PRINT
+  Serial.begin(115200);
+  Serial.println("NMRA Dcc Multifunction Motor Decoder Demo");
+  #endif
+
+  // Setup the Pins for the Fwd/Rev LED for Function 0 Headlight
+  pinMode(LED_PIN_FWD, OUTPUT);
+  pinMode(LED_PIN_REV, OUTPUT);
+
+  // Setup the Pins for the Motor H-Bridge Driver
+  pinMode(MOTOR_DIR_PIN, OUTPUT);
+  pinMode(MOTOR_PWM_PIN, OUTPUT);
+
+  
+  // Setup which External Interrupt, the Pin it's associated with that we're using and enable the Pull-Up 
+  Dcc.pin(DCC_PIN, 0);
+  
+  Dcc.init( MAN_ID_DIY, 10, FLAGS_MY_ADDRESS_ONLY | FLAGS_AUTO_FACTORY_DEFAULT, 0 );
+
+  // Uncomment to force CV Reset to Factory Defaults
+//  notifyCVResetFactoryDefault();
+
+  // Read the current CV values for vStart and vHigh
+  vStart = Dcc.getCV(CV_VSTART);
+  vHigh = Dcc.getCV(CV_VHIGH);
+}
+
+void loop()
+{
+  // You MUST call the NmraDcc.process() method frequently from the Arduino loop() function for correct library operation
+  Dcc.process();
+
+  // Handle Speed changes
+  if(lastSpeed != newSpeed)
+  {
+    lastSpeed = newSpeed;
+
+    // Stop if speed = 0 or 1
+    
+    if(newSpeed <= 1)
+      digitalWrite(MOTOR_PWM_PIN, LOW);
+
+    // Calculate PWM value in the range 1..255   
+    else
+    {
+      uint8_t vScaleFactor;
+      
+      if((vHigh > 1) && (vHigh > vStart))
+        vScaleFactor = vHigh - vStart;
+      else
+        vScaleFactor = 255 - vStart;
+
+      uint8_t modSpeed = newSpeed - 1;
+      uint8_t modSteps = numSpeedSteps - 1;
+      
+      uint8_t newPwm = (uint8_t) vStart + modSpeed * vScaleFactor / modSteps;
+
+      #ifdef DEBUG_PWM
+      Serial.print("New Speed: vStart: ");
+      Serial.print(vStart);
+      Serial.print(" vHigh: ");
+      Serial.print(vHigh);
+      Serial.print(" modSpeed: ");
+      Serial.print(modSpeed);
+      Serial.print(" vScaleFactor: ");
+      Serial.print(vScaleFactor);
+      Serial.print(" modSteps: ");
+      Serial.print(modSteps);
+      Serial.print(" newPwm: ");
+      Serial.println(newPwm);
+      #endif
+            
+      analogWrite(MOTOR_PWM_PIN, newPwm);
+    }
+  }
+  
+  // Handle Direction and Headlight changes
+  if((lastDirection != newDirection) || (lastLedState != newLedState))
+  {
+    lastDirection = newDirection;
+    lastLedState = newLedState;
+
+    digitalWrite(MOTOR_DIR_PIN, newDirection);
+
+    if(newLedState)
+    {
+      #ifdef DEBUG_FUNCTIONS
+      Serial.println("LED On");
+      #endif
+      digitalWrite(LED_PIN_FWD, newDirection ? LOW : HIGH);
+      digitalWrite(LED_PIN_REV, newDirection ? HIGH : LOW);
+    }
+    else
+    {
+      #ifdef DEBUG_FUNCTIONS
+      Serial.println("LED Off");
+      #endif
+      digitalWrite(LED_PIN_FWD, LOW);
+      digitalWrite(LED_PIN_REV, LOW);
+    }
+  }
+
+  // Handle resetting CVs back to Factory Defaults
+  if( FactoryDefaultCVIndex && Dcc.isSetCVReady())
+  {
+    FactoryDefaultCVIndex--; // Decrement first as initially it is the size of the array 
+    Dcc.setCV( FactoryDefaultCVs[FactoryDefaultCVIndex].CV, FactoryDefaultCVs[FactoryDefaultCVIndex].Value);
+  }
+}

library.properties

@@ -1,6 +1,6 @@
 name=NmraDcc
-version=2.0.0
+version=2.0.6
-author=Alex Shepherd, Wolfgang Kuffer, Geoff Bunza, Martin Pischky, Franz-Peter Müller, Sven (littleyoda)
+author=Alex Shepherd, Wolfgang Kuffer, Geoff Bunza, Martin Pischky, Franz-Peter Müller, Sven (littleyoda), Hans Tanner
 maintainer=Alex Shepherd <kiwi64ajs@gmail.com>
 sentence=Enables NMRA DCC Communication 
 paragraph=This library allows you to interface to a NMRA DCC track signal and receive DCC commands. The library has been tested on AVR ATTiny84/85 & ATMega88/168/328/32u4, ESP8266 and Teensy 3.x using the INT0/1 Hardware Interrupt and micros() ONLY and no longer uses Timer0 Compare Match B, which makes it much more portable to other platforms.