From 98071602c32694d98b02c22aa8018879212d3ae4 Mon Sep 17 00:00:00 2001
From: Harald Barth <haba@kth.se>
Date: Fri, 12 Mar 2021 22:12:13 +0100
Subject: [PATCH] Bugfix: Transmit packages of size MAX_PACKET_SIZE (5) as well

---
 DCC.cpp         | 8 ++++++++
 DCCWaveform.cpp | 3 ++-
 DCCWaveform.h   | 6 +++---
 version.h       | 4 +++-
 4 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/DCC.cpp b/DCC.cpp
index 854f9b2..e6b3c64 100644
--- a/DCC.cpp
+++ b/DCC.cpp
@@ -198,6 +198,10 @@ void DCC::setAccessory(int address, byte number, bool activate) {
   DCCWaveform::mainTrack.schedulePacket(b, 2, 4);      // Repeat the packet four times
 }
 
+//
+// writeCVByteMain: Write a byte with PoM on main. This writes
+// the 5 byte sized packet to implement this DCC function
+//
 void DCC::writeCVByteMain(int cab, int cv, byte bValue)  {
   byte b[5];
   byte nB = 0;
@@ -212,6 +216,10 @@ void DCC::writeCVByteMain(int cab, int cv, byte bValue)  {
   DCCWaveform::mainTrack.schedulePacket(b, nB, 4);
 }
 
+//
+// writeCVBitMain: Write a bit of a byte with PoM on main. This writes
+// the 5 byte sized packet to implement this DCC function
+//
 void DCC::writeCVBitMain(int cab, int cv, byte bNum, bool bValue)  {
   byte b[5];
   byte nB = 0;
diff --git a/DCCWaveform.cpp b/DCCWaveform.cpp
index c7baa9f..8da4e0c 100644
--- a/DCCWaveform.cpp
+++ b/DCCWaveform.cpp
@@ -256,7 +256,7 @@ void DCCWaveform::interrupt2() {
 
 // Wait until there is no packet pending, then make this pending
 void DCCWaveform::schedulePacket(const byte buffer[], byte byteCount, byte repeats) {
-  if (byteCount >= MAX_PACKET_SIZE) return; // allow for chksum
+  if (byteCount > MAX_PACKET_SIZE) return; // allow for chksum
   while (packetPending);
 
   byte checksum = 0;
@@ -264,6 +264,7 @@ void DCCWaveform::schedulePacket(const byte buffer[], byte byteCount, byte repea
     checksum ^= buffer[b];
     pendingPacket[b] = buffer[b];
   }
+  // buffer is MAX_PACKET_SIZE but pendingPacket is one bigger
   pendingPacket[byteCount] = checksum;
   pendingLength = byteCount + 1;
   pendingRepeats = repeats;
diff --git a/DCCWaveform.h b/DCCWaveform.h
index aad63ae..db6c7f7 100644
--- a/DCCWaveform.h
+++ b/DCCWaveform.h
@@ -29,7 +29,7 @@ const int  POWER_SAMPLE_OVERLOAD_WAIT = 20;
 // Number of preamble bits.
 const int   PREAMBLE_BITS_MAIN = 16;
 const int   PREAMBLE_BITS_PROG = 22;
-const byte   MAX_PACKET_SIZE = 5;  // NMRA standard exrtended packets 
+const byte   MAX_PACKET_SIZE = 5;  // NMRA standard extended packets, payload size WITHOUT checksum.
 
 // The WAVE_STATE enum is deliberately numbered because a change of order would be catastrophic
 // to the transform array.
@@ -119,7 +119,7 @@ class DCCWaveform {
     bool isMainTrack;
     MotorDriver*  motorDriver;
     // Transmission controller
-    byte transmitPacket[MAX_PACKET_SIZE];  // packet being transmitted
+    byte transmitPacket[MAX_PACKET_SIZE+1]; // +1 for checksum
     byte transmitLength;
     byte transmitRepeats;      // remaining repeats of transmission
     byte remainingPreambles;
@@ -127,7 +127,7 @@ class DCCWaveform {
     byte bits_sent;           // 0-8 (yes 9 bits) sent for current byte
     byte bytes_sent;          // number of bytes sent from transmitPacket
     WAVE_STATE state;         // wave generator state machine
-    byte pendingPacket[MAX_PACKET_SIZE];
+    byte pendingPacket[MAX_PACKET_SIZE+1]; // +1 for checksum
     byte pendingLength;
     byte pendingRepeats;
     int  lastCurrent;
diff --git a/version.h b/version.h
index 97b082c..64ef071 100644
--- a/version.h
+++ b/version.h
@@ -3,7 +3,9 @@
 
 #include "StringFormatter.h"
 
-#define VERSION "3.0.5"
+#define VERSION "3.0.6"
+// 3.0.6 Includes:
+// Fix Bug that did not let us transmit 5 byte sized packets like PoM
 // 3.0.5 Includes:
 // Fix Fn Key startup with loco ID and fix state change for F16-28
 // 3.0.4 Includes: