diff --git a/DCC.cpp b/DCC.cpp
index b0973bc..3876e23 100644
--- a/DCC.cpp
+++ b/DCC.cpp
@@ -46,8 +46,8 @@ const byte FN_GROUP_5=0x10;
 
 FSH* DCC::shieldName=NULL;
 
-void DCC::begin( FSH * motorShieldName, MotorDriver * mainDriver, MotorDriver* progDriver) {
-  shieldName=motorShieldName;
+void DCC::begin(const FSH * motorShieldName, MotorDriver * mainDriver, MotorDriver* progDriver) {
+  shieldName=(FSH *)motorShieldName;
   DIAG(F("<iDCC-EX V-%S / %S / %S G-%S>\n"), F(VERSION), F(ARDUINO_TYPE), shieldName, F(GITHUB_SHA));
 
   // Load stuff from EEprom
diff --git a/DCC.h b/DCC.h
index 7099056..524c05c 100644
--- a/DCC.h
+++ b/DCC.h
@@ -64,7 +64,7 @@ const byte MAX_LOCOS = 50;
 class DCC
 {
 public:
-  static void begin(FSH * motorShieldName, MotorDriver *mainDriver, MotorDriver *progDriver);
+  static void begin(const FSH * motorShieldName, MotorDriver *mainDriver, MotorDriver *progDriver);
   static void loop();
 
   // Public DCC API functions
diff --git a/DCCEXParser.cpp b/DCCEXParser.cpp
index 04546a3..7fb6fa9 100644
--- a/DCCEXParser.cpp
+++ b/DCCEXParser.cpp
@@ -732,10 +732,6 @@ bool DCCEXParser::parseD(Print *stream, int params, int p[])
         Diag::WITHROTTLE = onOff;
         return true;
 
-    case HASH_KEYWORD_DCC:
-        DCCWaveform::setDiagnosticSlowWave(params >= 1 && p[1] == HASH_KEYWORD_SLOW);
-        return true;
-
     case HASH_KEYWORD_PROGBOOST:
         DCC::setProgTrackBoost(true);
 	return true;
diff --git a/DCCTimer.cpp b/DCCTimer.cpp
index 15409ae..bbec1c1 100644
--- a/DCCTimer.cpp
+++ b/DCCTimer.cpp
@@ -28,50 +28,45 @@
  */
 
 #include "DCCTimer.h"
-#include "DIAG.h" 
 const int DCC_SIGNAL_TIME=58;  // this is the 58uS DCC 1-bit waveform half-cycle 
-const int DCC_SLOW_TIME=58*512;  // for <D DCC SLOW> command diagnostics 
+const long CLOCK_CYCLES=(F_CPU / 1000000 * DCC_SIGNAL_TIME) >>1;
 
 INTERRUPT_CALLBACK interruptHandler=0;
 
-
-void DCCTimer::begin(INTERRUPT_CALLBACK callback, bool slow) {
-  interruptHandler=callback;
-  // Initialise timer1 to trigger every 58us (DCC_SIGNAL_TIME)
-  noInterrupts();
-  
 #ifdef ARDUINO_ARCH_MEGAAVR
-      // Arduino unoWifi Rev2 and nanoEvery architectire 
-      long clockCycles=slow? (14*512) : 14;  // guesswork!!!!
-      DIAG(F("\nTimer unoWifi/nanoEvery F_CPU=%l c=%d"),F_CPU,clockCycles); 
-      TCB0.CCMP = clockCycles;
-      TCB0.INTFLAGS = TCB_CAPT_bm; // clear interrupt request flag
-      TCB0.INTCTRL = TCB_CAPT_bm;  // Enable the interrupt
-      TCB0.CNT = 0;
-      TCB0.CTRLA |= TCB_ENABLE_bm;  // start
-      #define ISR_NAME TCB0_INT_vect
+  // Arduino unoWifi Rev2 and nanoEvery architectire 
+  void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
+    interruptHandler=callback;
+    noInterrupts(); 
+    TCB0.CTRLB = TCB_CNTMODE_INT_gc & ~TCB_CCMPEN_bm; // timer compare mode with output disabled
+    TCB0.CTRLA = TCB_CLKSEL_CLKDIV2_gc; //   8 MHz ~ 0.125 us      
+    TCB0.CCMP =  CLOCK_CYCLES -1;  // 1 tick less for timer reset 
+    TCB0.INTFLAGS = TCB_CAPT_bm; // clear interrupt request flag
+    TCB0.INTCTRL = TCB_CAPT_bm;  // Enable the interrupt
+    TCB0.CNT = 0;
+    TCB0.CTRLA |= TCB_ENABLE_bm;  // start
+    interrupts();
+  }
 
-#else 
-
-      // Arduino nano, uno, mega
-      long clockCycles=((F_CPU / 1000000) * (slow? DCC_SLOW_TIME : DCC_SIGNAL_TIME)) >>1;
-      DIAG(F("\nTimer nano/uno/mega F_CPU=%l c=%d"),F_CPU,clockCycles); 
-      TCCR1A = 0;
-      ICR1 = clockCycles;
-      TCNT1 = 0;   
-      TCCR1B = _BV(WGM13) | _BV(CS10);     // Mode 8, clock select 1
-      TIMSK1 = _BV(TOIE1); // Enable Software interrupt
-      #define ISR_NAME TIMER1_OVF_vect
-#endif
+  // ISR called by timer interrupt every 58uS
+  ISR(TCB0_INT_vect){
+    TCB0.INTFLAGS = TCB_CAPT_bm;
+    interruptHandler();
+  }
   
-  interrupts();
-}
+#else 
+  // Arduino nano, uno, mega etc 
+  void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
+    interruptHandler=callback;
+    noInterrupts(); 
+    TCCR1A = 0;
+    ICR1 = CLOCK_CYCLES;
+    TCNT1 = 0;   
+    TCCR1B = _BV(WGM13) | _BV(CS10);     // Mode 8, clock select 1
+    TIMSK1 = _BV(TOIE1); // Enable Software interrupt
+    interrupts();
+  }
 
 // ISR called by timer interrupt every 58uS
-ISR(ISR_NAME)
-{
-#ifdef ARDUINO_ARCH_MEGAAVR
-    TCB0.INTFLAGS = TCB_CAPT_bm;
+  ISR(TIMER1_OVF_vect){ interruptHandler(); }
 #endif
-    if (interruptHandler) interruptHandler();
-}
diff --git a/DCCTimer.h b/DCCTimer.h
index 7f99acc..a388349 100644
--- a/DCCTimer.h
+++ b/DCCTimer.h
@@ -6,7 +6,7 @@ typedef void (*INTERRUPT_CALLBACK)();
 
 class DCCTimer {
   public:
-  static void begin(INTERRUPT_CALLBACK interrupt, bool slow=false);
+  static void begin(INTERRUPT_CALLBACK interrupt);
   private:
 };
 
diff --git a/DCCWaveform.cpp b/DCCWaveform.cpp
index 90db3ee..7d76e59 100644
--- a/DCCWaveform.cpp
+++ b/DCCWaveform.cpp
@@ -40,11 +40,6 @@ void DCCWaveform::begin(MotorDriver * mainDriver, MotorDriver * progDriver) {
   DCCTimer::begin(DCCWaveform::interruptHandler);     
 }
 
-void DCCWaveform::setDiagnosticSlowWave(bool slow) {  
-  DCCTimer::begin(DCCWaveform::interruptHandler, slow);     
-  DIAG(F("\nDCC SLOW WAVE %S\n"),slow?F("SET. DO NOT ADD LOCOS TO TRACK"):F("RESET")); 
-}
-
 void DCCWaveform::loop() {
   mainTrack.checkPowerOverload();
   progTrack.checkPowerOverload();
diff --git a/DCCWaveform.h b/DCCWaveform.h
index e3c05fd..c193545 100644
--- a/DCCWaveform.h
+++ b/DCCWaveform.h
@@ -46,7 +46,6 @@ class DCCWaveform {
   public:
     DCCWaveform( byte preambleBits, bool isMain);
     static void begin(MotorDriver * mainDriver, MotorDriver * progDriver);
-    static void setDiagnosticSlowWave(bool slow);
     static void loop();
     static DCCWaveform  mainTrack;
     static DCCWaveform  progTrack;