Very rough draft of DDS supporting the Arduio Zero and it's built-in DAC.

DDS.cpp

@@ -1,9 +1,63 @@
 #include <Arduino.h>
 #include "DDS.h"
 
+#ifdef __SAMD21G18A__
+
+// The SimpleAudioPlayerZero sample project found at:
+// https://www.arduino.cc/en/Tutorial/SimpleAudioPlayerZero
+// is an execellent reference for setting up the Timer/Counter
+#define TC_ISBUSY()   (TC5->COUNT16.STATUS.reg & TC_STATUS_SYNCBUSY)
+#define TC_WAIT()     while (TC_ISBUSY());
+#define TC_ENABLE()   TC5->COUNT16.CTRLA.reg |= TC_CTRLA_ENABLE; TC_WAIT();                    
+#define TC_RESET()    TC5->COUNT16.CTRLA.reg = TC_CTRLA_SWRST; TC_WAIT(); \
+                      while (TC5->COUNT16.CTRLA.bit.SWRST);
+#define TC_DISABLE()  TC5->COUNT16.CTRLA.reg &= ~TC_CTRLA_ENABLE; TC_WAIT();
+
+#endif
+
 // To start the DDS, we use Timer1, set to the reference clock
 // We use Timer2 for the PWM output, running as fast as feasible
 void DDS::start() {
+
+#ifdef DDS_DEBUG_SERIAL
+  // Print these debug statements (commont to both the AVR and the SAMD21)
+  Serial.print(F("DDS SysClk: "));
+  Serial.println(F_CPU/8);
+  Serial.print(F("DDS RefClk: "));
+  Serial.println(refclk, DEC);
+#endif
+
+#ifdef __SAMD21G18A__
+  // Enable the Generic Clock Generator 0 and configure for TC4 and TC5.
+  // We only need TC5, but they are configured together
+  GCLK->CLKCTRL.reg = (uint16_t) (GCLK_CLKCTRL_CLKEN | GCLK_CLKCTRL_GEN_GCLK0 | GCLK_CLKCTRL_ID(GCM_TC4_TC5)) ;
+  while (GCLK->STATUS.bit.SYNCBUSY);
+
+  TC_RESET();
+
+  // Set TC5 16 bit
+  TC5->COUNT16.CTRLA.reg |= TC_CTRLA_MODE_COUNT16;
+
+  // Set TC5 mode as match frequency
+  TC5->COUNT16.CTRLA.reg |= TC_CTRLA_WAVEGEN_MFRQ;
+  TC5->COUNT16.CTRLA.reg |= TC_CTRLA_PRESCALER_DIV1 | TC_CTRLA_ENABLE;
+  TC5->COUNT16.CC[0].reg = (uint16_t) (SystemCoreClock / DDS_REFCLK_DEFAULT - 1);
+  TC_WAIT()
+
+  // Configure interrupt
+  NVIC_DisableIRQ(TC5_IRQn);
+  NVIC_ClearPendingIRQ(TC5_IRQn);
+  NVIC_SetPriority(TC5_IRQn, 0);
+  NVIC_EnableIRQ(TC5_IRQn);
+
+  // Enable TC5 Interrupt
+  TC5->COUNT16.INTENSET.bit.MC0 = 1;
+  TC_WAIT();
+
+  //Configure the DAC
+  analogWriteResolution(8);
+  analogWrite(A0, 0);
+#else
   // Use the clkIO clock rate
   ASSR &= ~(_BV(EXCLK) | _BV(AS2));
   
@@ -45,10 +99,6 @@ void DDS::start() {
   TCCR1A = 0;
   ICR1 = ((F_CPU / 1) / refclk) - 1; 
   #ifdef DDS_DEBUG_SERIAL
-  Serial.print(F("DDS SysClk: "));
-  Serial.println(F_CPU/8);
-  Serial.print(F("DDS RefClk: "));
-  Serial.println(refclk, DEC);
     Serial.print(F("DDS ICR1: "));
     Serial.println(ICR1, DEC);
   #endif
@@ -60,14 +110,22 @@ void DDS::start() {
   DIDR0 |= _BV(0);
   ADCSRB = _BV(ADTS2) | _BV(ADTS1) | _BV(ADTS0);
   ADCSRA = _BV(ADEN) | _BV(ADSC) | _BV(ADATE) | _BV(ADIE) | _BV(ADPS2); // | _BV(ADPS0);    
+
+#endif
 }
 
 void DDS::stop() {
+#ifdef __SAMD21G18A__
+  TC_DISABLE();
+  TC_RESET();
+  analogWrite(A0, 0);
+#else
   // TODO: Stop the timers.
   #ifndef DDS_USE_ONLY_TIMER2
     TCCR1B = 0;
   #endif
     TCCR2B = 0;
+#endif
 }
 
 // Set our current sine wave frequency in Hz
@@ -89,6 +147,7 @@ ddsAccumulator_t DDS::calcFrequency(unsigned short freq) {
       newStep = (600.0 / (DDS_REFCLK_DEFAULT+DDS_REFCLK_OFFSET)) * pow(2,ACCUMULATOR_BITS);      
     }
   } else {
+    //TODO:  This doesn't work with the SAM21D... yet
     newStep = pow(2,ACCUMULATOR_BITS)*freq / (refclk+refclkOffset);
   }
   return newStep;
@@ -112,6 +171,13 @@ void DDS::clockTick() {
   if(running) {
     accumulator += stepRate;
     if(timeLimited && tickDuration == 0) {
+#ifdef __SAMD21G18A__
+  #ifdef DDS_IDLE_HIGH
+    analogWrite(A0, pow(2,COMPARATOR_BITS)/2);
+  #else
+    analogWrite(A0, 0);
+  #endif
+#else
   #ifndef DDS_PWM_PIN_3
       OCR2A = 0;
   #else
@@ -122,19 +188,31 @@ void DDS::clockTick() {
       // Set duty cycle to 0, effectively off
         OCR2B = 0;
   #endif
+  #endif
 #endif
       running = false;
       accumulator = 0;
     } else {
+#ifdef __SAMD21G18A__
+    analogWrite(A0, getDutyCycle());
+#else
   #ifdef DDS_PWM_PIN_3
       OCR2B = getDutyCycle();
   #else
       OCR2A = getDutyCycle();
+  #endif
 #endif
     }
     // Reduce our playback duration by one tick
     tickDuration--;
   } else {
+#ifdef __SAMD21G18A__
+  #ifdef DDS_IDLE_HIGH
+    analogWrite(A0, pow(2,COMPARATOR_BITS)/2);
+  #else
+    analogWrite(A0, 0);
+  #endif
+#else
     // Hold it low
   #ifndef DDS_PWM_PIN_3
     OCR2A = 0;
@@ -147,10 +225,11 @@ void DDS::clockTick() {
       OCR2B = 0;
     #endif
   #endif
+#endif
   }
 }
 
-uint8_t DDS::getDutyCycle() {
+ddsComparitor_t DDS::getDutyCycle() {
   #if ACCUMULATOR_BIT_SHIFT >= 24
     uint16_t phAng;
   #else
@@ -173,3 +252,4 @@ uint8_t DDS::getDutyCycle() {
   scaled += 128>>(8-COMPARATOR_BITS);
   return scaled;
 }
+

DDS.h

@@ -1,12 +1,19 @@
 #ifndef _DDS_H_
 #define _DDS_H_
-
+#include <Arduino.h>
 #include <avr/pgmspace.h>
 
+// Just a little reminder
+#ifndef __SAMD21G18A__
+#warning Experimental support for ArduinoZero.  Not yet complete
+#endif 
+
 // Use pin 3 for PWM? If not defined, use pin 11
 // Quality on pin 3 is higher than on 11, as it can be clocked faster
 // when the COMPARATOR_BITS value is less than 8
+#ifndef __SAMD21G18A__
 #define DDS_PWM_PIN_3
+#endif
 
 // Normally, we turn on timer2 and timer1, and have ADC sampling as our clock
 // Define this to only use Timer2, and not start the ADC clock
@@ -14,7 +21,9 @@
 
 // Use a short (16 bit) accumulator. Phase accuracy is reduced, but speed
 // is increased, along with a reduction in memory use.
+#ifndef __SAMD21G18A__
 #define SHORT_ACCUMULATOR
+#endif
 
 #ifdef SHORT_ACCUMULATOR
 #define ACCUMULATOR_BITS      16
@@ -35,10 +44,17 @@ typedef uint32_t ddsAccumulator_t;
 // 8 = 62.5kHz PWM
 // 7 = 125kHz PWM
 // 6 = 250kHz PWM
-#ifdef DDS_PWM_PIN_3
+#ifdef __SAMD21G18A__
+//TODO: 10 bit resolution for the Zero's DAC.  
+//Doesn't work just yet, so keep 8-bit for now.
+#define COMPARATOR_BITS       8
+typedef uint8_t ddsComparitor_t;
+#elif defined(DDS_PWM_PIN_3)
 #define COMPARATOR_BITS       6
+typedef uint8_t ddsComparitor_t;
 #else // When using pin 11, we always want 8 bits
 #define COMPARATOR_BITS       8
+typedef uint8_t ddsComparitor_t;
 #endif
 
 // This is how often we'll perform a phase advance, as well as ADC sampling
@@ -46,8 +62,13 @@ typedef uint32_t ddsAccumulator_t;
 // expense of CPU time. It maxes out around 62000 (TBD)
 // May be overridden in the sketch to improve performance
 #ifndef DDS_REFCLK_DEFAULT
+  #ifdef __SAMD21G18A__
+    #define DDS_REFCLK_DEFAULT     44100
+  #else
     #define DDS_REFCLK_DEFAULT     9600
   #endif
+#endif
+
 // As each Arduino crystal is a little different, this can be fine tuned to
 // provide more accurate frequencies. Adjustments in the range of hundreds
 // is a good start.
@@ -61,7 +82,7 @@ typedef uint32_t ddsAccumulator_t;
 #endif
 
 // Output some of the calculations and information about the DDS over serial
-//#define DDS_DEBUG_SERIAL
+#define DDS_DEBUG_SERIAL
 
 // When defined, use the 1024 element sine lookup table. This improves phase
 // accuracy, at the cost of more flash and CPU requirements.
@@ -202,7 +223,7 @@ public:
     return refclkOffset;
   }
   
-  uint8_t getDutyCycle();
+  ddsComparitor_t getDutyCycle();
 
   // Set a scaling factor. To keep things quick, this is a power of 2 value.
   // Set it with 0 for lowest (which will be off), 8 is highest.
@@ -222,7 +243,7 @@ private:
   volatile ddsAccumulator_t stepRate;
   ddsAccumulator_t refclk;
   int16_t refclkOffset;
-  static DDS *sDDS;
+  //static _DDS *sDDS;
 };
 
 #endif /* _DDS_H_ */