PWM pin implementation

DCCTimer.cpp

@@ -25,6 +25,21 @@
  *  DCCEX works on a single timer interrupt at a regular 58uS interval.
  *  The DCCWaveform class generates the signals to the motor shield  
  *  based on this timer. 
+ *  
+ *  If the motor drivers are BOTH configured to use the correct 2 pins for the architecture,
+ *  (see isPWMPin() function. )
+ *  then this allows us to use a hardware driven pin switching arrangement which is
+ *  achieved by setting the duty cycle of the NEXT clock interrupt to 0% or 100% depending on 
+ *  the required pin state. (see setPWM())  
+ *  This is more accurate than the software interrupt but at the expense of 
+ *  limiting the choice of available pins. 
+ *  Fortunately, a standard motor shield on a Mega uses pins that qualify for PWM... 
+ *  Other shields may be jumpered to PWM pins or run directly using the software interrupt.
+ *  
+ *  Because the PWM-based waveform is effectively set half a cycle after the software version,
+ *  it is not acceptable to drive the two tracks on different methiods or it would cause
+ *  problems for <1 JOIN> etc.
+ *  
  */
 
 #include "DCCTimer.h"
@@ -35,13 +50,14 @@ INTERRUPT_CALLBACK interruptHandler=0;
 
 #ifdef ARDUINO_ARCH_MEGAAVR
   // Arduino unoWifi Rev2 and nanoEvery architectire 
+  
   void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
     interruptHandler=callback;
     noInterrupts(); 
     ADC0.CTRLC = (ADC0.CTRLC & 0b00110000) | 0b01000011;  // speed up analogRead sample time   
     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.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;
@@ -55,12 +71,29 @@ INTERRUPT_CALLBACK interruptHandler=0;
     interruptHandler();
   }
 
+  bool DCCTimer::isPWMPin(byte pin) {
+       return false;  // TODO what are the relevant pins? 
+  }
+
+ void DCCTimer::setPWM(byte pin, bool high) {
+    // TODO what are the relevant pins?
+ }
+
   void   DCCTimer::getSimulatedMacAddress(byte mac[6]) {
-    memcpy(mac,&SIGROW.SERNUM0,6);  // serial number
+    memcpy(mac,(void *) &SIGROW.SERNUM0,6);  // serial number
   }
 
 #else 
   // Arduino nano, uno, mega etc
+#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
+    #define TIMER1_A_PIN   11
+    #define TIMER1_B_PIN   12
+    #define TIMER1_C_PIN   13
+#else
+   #define TIMER1_A_PIN   9
+   #define TIMER1_B_PIN   10
+#endif
+
   void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
     interruptHandler=callback;
     noInterrupts();          
@@ -76,6 +109,34 @@ INTERRUPT_CALLBACK interruptHandler=0;
 // ISR called by timer interrupt every 58uS
   ISR(TIMER1_OVF_vect){ interruptHandler(); }
 
+// Alternative pin manipulation via PWM control.
+  bool DCCTimer::isPWMPin(byte pin) {
+       return pin==TIMER1_A_PIN 
+           || pin==TIMER1_B_PIN
+       #ifdef TIMER1_C_PIN 
+           || pin==TIMER1_C_PIN
+       #endif       
+       ;
+  }
+
+ void DCCTimer::setPWM(byte pin, bool high) {
+    if (pin==TIMER1_A_PIN) {
+      TCCR1A |= _BV(COM1A1);
+      OCR1A= high?1024:0;
+    }
+    else if (pin==TIMER1_B_PIN) { 
+      TCCR1A |= _BV(COM1B1);
+      OCR1B= high?1024:0;
+    }
+ #ifdef TIMER1_C_PIN 
+    else if (pin==TIMER1_C_PIN) { 
+      TCCR1A |= _BV(COM1C1);
+      OCR1C= high?1024:0;
+    }
+ #endif       
+ }
+
+
   #include <avr/boot.h> 
   void DCCTimer::getSimulatedMacAddress(byte mac[6]) {
     for (byte i=0; i<6; i++) mac[i]=boot_signature_byte_get(0x0E + i);

DCCTimer.h

@@ -8,6 +8,8 @@ class DCCTimer {
   public:
   static void begin(INTERRUPT_CALLBACK interrupt);
   static void getSimulatedMacAddress(byte mac[6]);
+  static bool isPWMPin(byte pin);
+  static void setPWM(byte pin, bool high);
   private:
 };
 

DCCWaveform.cpp

@@ -39,6 +39,9 @@ void DCCWaveform::begin(MotorDriver * mainDriver, MotorDriver * progDriver) {
   progTripValue = progDriver->mA2raw(TRIP_CURRENT_PROG); // need only calculate once hence static
   mainTrack.setPowerMode(POWERMODE::OFF);      
   progTrack.setPowerMode(POWERMODE::OFF);
+  MotorDriver::usePWM= mainDriver->isPWMCapable() && progDriver->isPWMCapable();
+  if (MotorDriver::usePWM) DIAG(F("\nWaveform using PWM pins for accuracy."));
+  else  DIAG(F("\nWaveform accuracy limited by signal pin configuration."));
   DCCTimer::begin(DCCWaveform::interruptHandler);     
 }
 

MotorDriver.cpp

@@ -18,6 +18,7 @@
  */
 #include <Arduino.h>
 #include "MotorDriver.h"
+#include "DCCTimer.h"
 #include "DIAG.h"
 
 #define setHIGH(fastpin)  *fastpin.inout |= fastpin.maskHIGH
@@ -25,6 +26,7 @@
 #define isHIGH(fastpin)   (*fastpin.inout & fastpin.maskHIGH)
 #define isLOW(fastpin)    (!isHIGH(fastpin))
 
+bool MotorDriver::usePWM=false;
        
 MotorDriver::MotorDriver(byte power_pin, byte signal_pin, byte signal_pin2, int8_t brake_pin,
                          byte current_pin, float sense_factor, unsigned int trip_milliamps, byte fault_pin) {
@@ -68,6 +70,11 @@ MotorDriver::MotorDriver(byte power_pin, byte signal_pin, byte signal_pin2, int8
   rawCurrentTripValue=(int)(trip_milliamps / sense_factor);
 }
 
+bool MotorDriver::isPWMCapable() {
+    return (!dualSignal) && DCCTimer::isPWMPin(signalPin); 
+}
+
+
 void MotorDriver::setPower(bool on) {
   if (on) {
     // toggle brake before turning power on - resets overcurrent error
@@ -94,17 +101,21 @@ void MotorDriver::setBrake(bool on) {
 }
 
 void MotorDriver::setSignal( bool high) {
-   if (high) {
-      setHIGH(fastSignalPin);
-      if (dualSignal) setLOW(fastSignalPin2);
+   if (usePWM) {
+    DCCTimer::setPWM(signalPin,high);
    }
    else {
-      setLOW(fastSignalPin);
-      if (dualSignal) setHIGH(fastSignalPin2);
+     if (high) {
+        setHIGH(fastSignalPin);
+        if (dualSignal) setLOW(fastSignalPin2);
+     }
+     else {
+        setLOW(fastSignalPin);
+        if (dualSignal) setHIGH(fastSignalPin2);
+     }
    }
 }
 
-
 int MotorDriver::getCurrentRaw() {
   int current = analogRead(currentPin);
   if (faultPin != UNUSED_PIN && isLOW(fastFaultPin) && isHIGH(fastPowerPin))

MotorDriver.h

@@ -44,7 +44,9 @@ class MotorDriver {
     inline int getRawCurrentTripValue() {
 	    return rawCurrentTripValue;
     }
-
+    bool isPWMCapable();
+    static bool usePWM;
+    
   private:
     void  getFastPin(const FSH* type,int pin, bool input, FASTPIN & result);
     void  getFastPin(const FSH* type,int pin, FASTPIN & result) {