diff --git a/DCCWaveform.cpp b/DCCWaveform.cpp
index 211aac3..5c4d6d2 100644
--- a/DCCWaveform.cpp
+++ b/DCCWaveform.cpp
@@ -127,10 +127,11 @@ volatile bool DCCWaveform::railcomActive=false;     // switched on by user
 volatile bool DCCWaveform::railcomDebug=false;     // switched on by user
 volatile bool DCCWaveform::railcomSampleWindow=false; // true during packet transmit
 volatile byte DCCWaveform::railcomCutoutCounter=0;    // cyclic cutout
+volatile byte DCCWaveform::railcomLastAddressHigh=0;
+volatile byte DCCWaveform::railcomLastAddressLow=0;
 
 bool DCCWaveform::setRailcom(bool on, bool debug) {
   if (on && railcomPossible) {
-    // TODO check possible
     railcomActive=true;
     railcomDebug=debug;
   }
@@ -233,6 +234,12 @@ void DCCWaveform::promotePendingPacket() {
         return;
       }
 
+    // Remember address bytes of last sent packet so that Railcom can
+    // work out where the channel2 data came from.
+    railcomLastAddressHigh=transmitPacket[0];
+    railcomLastAddressLow =transmitPacket[1];
+  
+    
     if (packetPending) {
         // Copy pending packet to transmit packet
         // a fixed length memcpy is faster than a variable length loop for these small lengths
diff --git a/DCCWaveform.h b/DCCWaveform.h
index 97cf94b..8979c28 100644
--- a/DCCWaveform.h
+++ b/DCCWaveform.h
@@ -100,6 +100,14 @@ class DCCWaveform {
       railcomPossible=yes;
       if (!yes) setRailcom(false,false);
     };
+    inline static uint16_t getRailcomLastLocoAddress() {
+      // first 2 bits 00=short loco, 11=long loco , 01/10 = accessory
+      byte addressType=railcomLastAddressHigh & 0xC0;
+      if (addressType==0xC0) return ((railcomLastAddressHigh & 0x3f)<<8) | railcomLastAddressLow;
+      if (addressType==0x00) return railcomLastAddressHigh & 0x3F;
+      return 0; 
+    }
+
   private:
 #ifndef ARDUINO_ARCH_ESP32
     volatile bool packetPending;
@@ -129,6 +137,7 @@ class DCCWaveform {
     static volatile bool railcomDebug;     // switched on by user
     static volatile bool railcomSampleWindow; // when safe to sample
     static volatile byte railcomCutoutCounter; // incremented for each cutout
+    static volatile byte railcomLastAddressHigh,railcomLastAddressLow;
     static bool cutoutNextTime;   // railcom
 #ifdef ARDUINO_ARCH_ESP32
   static RMTChannel *rmtMainChannel;
diff --git a/IO_I2CRailcom.h b/IO_I2CRailcom.h
index 0daa368..9dcccdf 100644
--- a/IO_I2CRailcom.h
+++ b/IO_I2CRailcom.h
@@ -58,7 +58,7 @@ class I2CRailcom : public IODevice {
 private: 
   // SC16IS752 defines
   uint8_t _UART_CH=0x00; // channel 0 or 1 flips each loop if npins>1
-  byte _inbuf[65];
+  byte _inbuf[12];
   byte _outbuf[2];
   byte cutoutCounter[2]; 
   Railcom * _channelMonitors[2]; 
@@ -118,7 +118,7 @@ public:
     // Read incoming raw Railcom data, and process accordingly
 
     auto inlength = UART_ReadRegister(REG_RXLV);
-    if (inlength==0) return; 
+    
     if (inlength> sizeof(_inbuf)) inlength=sizeof(_inbuf); 
     _inbuf[0]=0;
     if (inlength>0) {
diff --git a/Railcom.cpp b/Railcom.cpp
index ef7b7f1..dc880a9 100644
--- a/Railcom.cpp
+++ b/Railcom.cpp
@@ -54,7 +54,7 @@
 #include "EXRAIL3.h"
 #include "DIAG.h"
 
-//#define DIAG_I2CRailcom_data
+#define DIAG_I2CRailcom_data
 
 
   /** Table for 8-to-6 decoding of railcom data. This table can be indexed by the
@@ -135,6 +135,10 @@ const uint8_t HIGHFLASH decode[256] =
         RMOB_LOGON_ENABLE_FEEDBACK = 15,
 };
 
+// each railcom block is represented by an instance of this class.
+// The blockvpin is the vpin associated with this block for the purposes of 
+// a HAL driver for the railcom detection and the EXRAIL ONBLOCKENTER/ONBLOCKEXIT
+
 Railcom::Railcom(uint16_t blockvpin) {
     haveHigh=false;
     haveLow=false;
@@ -143,23 +147,33 @@ Railcom::Railcom(uint16_t blockvpin) {
     vpin=blockvpin;
 }
 
-    /* returns -1: Call again next packet
-                0: No loco on track
-               >0: loco id
-    */
 void Railcom::process(uint8_t * inbound, uint8_t length) {
+    
+    
     #ifdef DIAG_I2CRailcom_data
-      DIAG(F("Railcom %d RX FIFO Data, %d"), vpin,length);
-      for (int i = 0; i < 2; i++){
-        if (inbound[i]) DIAG(F("[0x%x]: 0x%x"), i, inbound[i]);  
-      }
+    static const char hexchars[]="0123456789ABCDEF";
+    if (length>2) {  
+        Serial.print("R ");
+        for (byte i=0;i<length;i++) {
+          if (i==2) Serial.write(' ');
+          Serial.write(hexchars[inbound[i]>>4]);
+          Serial.write(hexchars[inbound[i]& 0x0F ]);
+        }
+        Serial.println();
+    }
+    
     #endif
+    if (length<2 || (inbound[0]==0 && inbound[1]==0)) {
+        noData();
+        return;
+    }
+
     auto v1=GETHIGHFLASH(decode,inbound[0]);
-    auto v2=(length>2) ? GETHIGHFLASH(decode,inbound[1]):0x0;
+    auto v2=(length>1) ? GETHIGHFLASH(decode,inbound[1]):INV;
     uint16_t packet=(v1<<6) | (v2 & 0x3f);
     // packet is 12 bits TTTTDDDDDDDD
-    auto type=packet>>8;   
-    auto data= packet & 0xFF;
+    byte type=(packet>>8) & 0x0F;   
+    byte data= packet & 0xFF;
     if (type==RMOB_ADRHIGH) {
         holdoverHigh=data;
         haveHigh=true;
@@ -174,16 +188,7 @@ void Railcom::process(uint8_t * inbound, uint8_t length) {
         return; /* ignore*/
         }
     else {
-        if (packetsWithNoData>MAX_WAIT_FOR_GLITCH) {
-            // treat as no loco
-            haveHigh=false;
-            haveLow=false;
-            // Previous loco (if any) is exiting block  
-            blockEvent(false);
-            locoOnTrack=0;
-            return ; 
-        }
-        packetsWithNoData++;
+        noData();
         return; // need more data          
     }    
     if (haveHigh && haveLow) {
@@ -202,3 +207,16 @@ void Railcom::blockEvent(bool entering) {
     if (locoOnTrack) RMFT3::blockEvent(vpin,locoOnTrack,entering);
     #endif
 }
+
+void Railcom::noData() {
+    if (packetsWithNoData>MAX_WAIT_FOR_GLITCH) return; 
+    if (packetsWithNoData==MAX_WAIT_FOR_GLITCH) {
+            // treat as no loco
+            haveHigh=false;
+            haveLow=false;
+            // Previous loco (if any) is exiting block  
+            blockEvent(false);
+            locoOnTrack=0;
+        }
+        packetsWithNoData++;
+}
diff --git a/Railcom.h b/Railcom.h
index b16945e..c84d55b 100644
--- a/Railcom.h
+++ b/Railcom.h
@@ -34,6 +34,7 @@ class Railcom {
   
   private:
   void blockEvent(bool entering);
+  void noData();
   uint16_t locoOnTrack;
   uint16_t vpin;
  uint8_t holdoverHigh,holdoverLow;