From 26dffa3be318d5ba01c424067cc2c2e4d7d97c60 Mon Sep 17 00:00:00 2001
From: Asbelos <asbelos@btinternet.com>
Date: Wed, 3 Jun 2020 09:42:17 +0100
Subject: [PATCH] Added DCC api readCVBit and getLocoId

Sanity check needed
---
 DCC.cpp | 27 +++++++++++++++++++++++++++
 DCC.h   |  2 ++
 2 files changed, 29 insertions(+)

diff --git a/DCC.cpp b/DCC.cpp
index 79e42a3..722a14f 100644
--- a/DCC.cpp
+++ b/DCC.cpp
@@ -130,6 +130,13 @@ bool DCC::verifyCVBit(int cv, byte bNum, bool bValue)  {
   return DCCWaveform::progTrack.schedulePacketWithAck(message, sizeof(message), 5);           // NMRA recommends 6 write or reset packets for decoder recovery time
 }
 
+int DCC::readCVBit(int cv, byte bNum)  {
+  if (bNum>=8) return -1;
+   if (verifyCVBit(cv, bNum,true)) return 1; 
+   // failed verify might be a zero, or an error so must check again  
+   if (verifyCVBit(cv, bNum,false)) return 0; 
+   return -1;
+}
 
 
 int DCC::readCV(int cv)  {
@@ -164,6 +171,26 @@ void DCC::loop()  {
   }
 }
 
+int DCC::getLocoId() {
+  switch (readCVBit(29,5)) {
+    case 1:  
+           // long address : get CV#17 and CV#18
+           {
+            int cv17=readCV(17);
+           
+           if  (cv17<0) break;
+           int cv18=readCV(18);
+           if  (cv18<0) break;
+           return cv18 + ((cv17 - 192) <<8);
+           }
+    case 0: // short address in CV1  
+           return readCV(1);
+    default: // No response or loco
+           break;
+  }
+  return -1;
+}
+
 ///// Private helper functions below here /////////////////////
 
 byte DCC::cv1(byte opcode, int cv)  {
diff --git a/DCC.h b/DCC.h
index 041e576..7f9e98a 100644
--- a/DCC.h
+++ b/DCC.h
@@ -13,6 +13,7 @@ class DCC {
   // Public DCC API functions
   static void setThrottle( uint16_t cab, uint8_t tSpeed, bool tDirection);
   static int  readCV(int cv);
+  static int  readCVBit(int cv, byte bNum);  // -1 for error
   static bool writeCVByte(int cv, byte bValue) ;
   static bool verifyCVByte(int cv,byte bValue);
   static bool writeCVBit(int cv, byte bNum, bool bValue);
@@ -23,6 +24,7 @@ class DCC {
   static void setFunction( int cab, byte fByte);
   static void setAccessory(int aAdd, byte aNum, bool activate) ;
   static bool writeTextPacket( byte *b, int nBytes);
+  static int getLocoId();
 
 private: 
   struct LOCO {