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

This commit is contained in:
Jake-B 2015-08-16 20:17:36 -04:00
parent c679bec886
commit fdaa602401
2 changed files with 154 additions and 53 deletions
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172
DDS.cpp
View File

@ -1,41 +1,95 @@
#include <Arduino.h> #include <Arduino.h>
#include "DDS.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 // To start the DDS, we use Timer1, set to the reference clock
// We use Timer2 for the PWM output, running as fast as feasible // We use Timer2 for the PWM output, running as fast as feasible
void DDS::start() { 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 // Use the clkIO clock rate
ASSR &= ~(_BV(EXCLK) | _BV(AS2)); ASSR &= ~(_BV(EXCLK) | _BV(AS2));
// First, the timer for the PWM output // First, the timer for the PWM output
// Setup the timer to use OC2B (pin 3) in fast PWM mode with a configurable top // Setup the timer to use OC2B (pin 3) in fast PWM mode with a configurable top
// Run it without the prescaler // Run it without the prescaler
#ifdef DDS_PWM_PIN_3 #ifdef DDS_PWM_PIN_3
TCCR2A = (TCCR2A | _BV(COM2B1)) & ~(_BV(COM2B0) | _BV(COM2A1) | _BV(COM2A0)) | TCCR2A = (TCCR2A | _BV(COM2B1)) & ~(_BV(COM2B0) | _BV(COM2A1) | _BV(COM2A0)) |
_BV(WGM21) | _BV(WGM20); _BV(WGM21) | _BV(WGM20);
TCCR2B = (TCCR2B & ~(_BV(CS22) | _BV(CS21))) | _BV(CS20) | _BV(WGM22); TCCR2B = (TCCR2B & ~(_BV(CS22) | _BV(CS21))) | _BV(CS20) | _BV(WGM22);
#else #else
// Alternatively, use pin 11 // Alternatively, use pin 11
// Enable output compare on OC2A, toggle mode // Enable output compare on OC2A, toggle mode
TCCR2A = _BV(COM2A1) | _BV(WGM21) | _BV(WGM20); TCCR2A = _BV(COM2A1) | _BV(WGM21) | _BV(WGM20);
//TCCR2A = (TCCR2A | _BV(COM2A1)) & ~(_BV(COM2A0) | _BV(COM2B1) | _BV(COM2B0)) | //TCCR2A = (TCCR2A | _BV(COM2A1)) & ~(_BV(COM2A0) | _BV(COM2B1) | _BV(COM2B0)) |
// _BV(WGM21) | _BV(WGM20); // _BV(WGM21) | _BV(WGM20);
TCCR2B = _BV(CS20); TCCR2B = _BV(CS20);
#endif #endif
// Set the top limit, which will be our duty cycle accuracy. // Set the top limit, which will be our duty cycle accuracy.
// Setting Comparator Bits smaller will allow for higher frequency PWM, // Setting Comparator Bits smaller will allow for higher frequency PWM,
// with the loss of resolution. // with the loss of resolution.
#ifdef DDS_PWM_PIN_3 #ifdef DDS_PWM_PIN_3
OCR2A = pow(2,COMPARATOR_BITS)-1; OCR2A = pow(2,COMPARATOR_BITS)-1;
OCR2B = 0; OCR2B = 0;
#else #else
OCR2A = 0; OCR2A = 0;
#endif #endif
#ifdef DDS_USE_ONLY_TIMER2 #ifdef DDS_USE_ONLY_TIMER2
TIMSK2 |= _BV(TOIE2); TIMSK2 |= _BV(TOIE2);
#endif #endif
// Second, setup Timer1 to trigger the ADC interrupt // Second, setup Timer1 to trigger the ADC interrupt
// This lets us use decoding functions that run at the same reference // This lets us use decoding functions that run at the same reference
@ -44,14 +98,10 @@ void DDS::start() {
TCCR1B = _BV(CS10) | _BV(WGM13) | _BV(WGM12); TCCR1B = _BV(CS10) | _BV(WGM13) | _BV(WGM12);
TCCR1A = 0; TCCR1A = 0;
ICR1 = ((F_CPU / 1) / refclk) - 1; ICR1 = ((F_CPU / 1) / refclk) - 1;
#ifdef DDS_DEBUG_SERIAL #ifdef DDS_DEBUG_SERIAL
Serial.print(F("DDS SysClk: ")); Serial.print(F("DDS ICR1: "));
Serial.println(F_CPU/8); Serial.println(ICR1, DEC);
Serial.print(F("DDS RefClk: ")); #endif
Serial.println(refclk, DEC);
Serial.print(F("DDS ICR1: "));
Serial.println(ICR1, DEC);
#endif
// Configure the ADC here to automatically run and be triggered off Timer1 // Configure the ADC here to automatically run and be triggered off Timer1
ADMUX = _BV(REFS0) | _BV(ADLAR) | 0; // Channel 0, shift result left (ADCH used) ADMUX = _BV(REFS0) | _BV(ADLAR) | 0; // Channel 0, shift result left (ADCH used)
@ -60,14 +110,22 @@ void DDS::start() {
DIDR0 |= _BV(0); DIDR0 |= _BV(0);
ADCSRB = _BV(ADTS2) | _BV(ADTS1) | _BV(ADTS0); ADCSRB = _BV(ADTS2) | _BV(ADTS1) | _BV(ADTS0);
ADCSRA = _BV(ADEN) | _BV(ADSC) | _BV(ADATE) | _BV(ADIE) | _BV(ADPS2); // | _BV(ADPS0); ADCSRA = _BV(ADEN) | _BV(ADSC) | _BV(ADATE) | _BV(ADIE) | _BV(ADPS2); // | _BV(ADPS0);
#endif
} }
void DDS::stop() { void DDS::stop() {
#ifdef __SAMD21G18A__
TC_DISABLE();
TC_RESET();
analogWrite(A0, 0);
#else
// TODO: Stop the timers. // TODO: Stop the timers.
#ifndef DDS_USE_ONLY_TIMER2 #ifndef DDS_USE_ONLY_TIMER2
TCCR1B = 0; TCCR1B = 0;
#endif
TCCR2B = 0;
#endif #endif
TCCR2B = 0;
} }
// Set our current sine wave frequency in Hz // 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); newStep = (600.0 / (DDS_REFCLK_DEFAULT+DDS_REFCLK_OFFSET)) * pow(2,ACCUMULATOR_BITS);
} }
} else { } else {
//TODO: This doesn't work with the SAM21D... yet
newStep = pow(2,ACCUMULATOR_BITS)*freq / (refclk+refclkOffset); newStep = pow(2,ACCUMULATOR_BITS)*freq / (refclk+refclkOffset);
} }
return newStep; return newStep;
@ -112,45 +171,65 @@ void DDS::clockTick() {
if(running) { if(running) {
accumulator += stepRate; accumulator += stepRate;
if(timeLimited && tickDuration == 0) { if(timeLimited && tickDuration == 0) {
#ifndef DDS_PWM_PIN_3 #ifdef __SAMD21G18A__
OCR2A = 0; #ifdef DDS_IDLE_HIGH
analogWrite(A0, pow(2,COMPARATOR_BITS)/2);
#else
analogWrite(A0, 0);
#endif
#else #else
#ifdef DDS_IDLE_HIGH #ifndef DDS_PWM_PIN_3
OCR2A = 0;
#else
#ifdef DDS_IDLE_HIGH
// Set the duty cycle to 50% // Set the duty cycle to 50%
OCR2B = pow(2,COMPARATOR_BITS)/2; OCR2B = pow(2,COMPARATOR_BITS)/2;
#else #else
// Set duty cycle to 0, effectively off // Set duty cycle to 0, effectively off
OCR2B = 0; OCR2B = 0;
#endif #endif
#endif
#endif #endif
running = false; running = false;
accumulator = 0; accumulator = 0;
} else { } else {
#ifdef DDS_PWM_PIN_3 #ifdef __SAMD21G18A__
OCR2B = getDutyCycle(); analogWrite(A0, getDutyCycle());
#else #else
#ifdef DDS_PWM_PIN_3
OCR2B = getDutyCycle();
#else
OCR2A = getDutyCycle(); OCR2A = getDutyCycle();
#endif
#endif #endif
} }
// Reduce our playback duration by one tick // Reduce our playback duration by one tick
tickDuration--; tickDuration--;
} else { } else {
#ifdef __SAMD21G18A__
#ifdef DDS_IDLE_HIGH
analogWrite(A0, pow(2,COMPARATOR_BITS)/2);
#else
analogWrite(A0, 0);
#endif
#else
// Hold it low // Hold it low
#ifndef DDS_PWM_PIN_3 #ifndef DDS_PWM_PIN_3
OCR2A = 0; OCR2A = 0;
#else #else
#ifdef DDS_IDLE_HIGH #ifdef DDS_IDLE_HIGH
// Set the duty cycle to 50% // Set the duty cycle to 50%
OCR2B = pow(2,COMPARATOR_BITS)/2; OCR2B = pow(2,COMPARATOR_BITS)/2;
#else #else
// Set duty cycle to 0, effectively off // Set duty cycle to 0, effectively off
OCR2B = 0; OCR2B = 0;
#endif #endif
#endif
#endif #endif
} }
} }
uint8_t DDS::getDutyCycle() { ddsComparitor_t DDS::getDutyCycle() {
#if ACCUMULATOR_BIT_SHIFT >= 24 #if ACCUMULATOR_BIT_SHIFT >= 24
uint16_t phAng; uint16_t phAng;
#else #else
@ -173,3 +252,4 @@ uint8_t DDS::getDutyCycle() {
scaled += 128>>(8-COMPARATOR_BITS); scaled += 128>>(8-COMPARATOR_BITS);
return scaled; return scaled;
} }

33
DDS.h
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@ -1,12 +1,19 @@
#ifndef _DDS_H_ #ifndef _DDS_H_
#define _DDS_H_ #define _DDS_H_
#include <Arduino.h>
#include <avr/pgmspace.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 // 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 // Quality on pin 3 is higher than on 11, as it can be clocked faster
// when the COMPARATOR_BITS value is less than 8 // when the COMPARATOR_BITS value is less than 8
#ifndef __SAMD21G18A__
#define DDS_PWM_PIN_3 #define DDS_PWM_PIN_3
#endif
// Normally, we turn on timer2 and timer1, and have ADC sampling as our clock // 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 // 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 // Use a short (16 bit) accumulator. Phase accuracy is reduced, but speed
// is increased, along with a reduction in memory use. // is increased, along with a reduction in memory use.
#ifndef __SAMD21G18A__
#define SHORT_ACCUMULATOR #define SHORT_ACCUMULATOR
#endif
#ifdef SHORT_ACCUMULATOR #ifdef SHORT_ACCUMULATOR
#define ACCUMULATOR_BITS 16 #define ACCUMULATOR_BITS 16
@ -35,10 +44,17 @@ typedef uint32_t ddsAccumulator_t;
// 8 = 62.5kHz PWM // 8 = 62.5kHz PWM
// 7 = 125kHz PWM // 7 = 125kHz PWM
// 6 = 250kHz 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 #define COMPARATOR_BITS 6
typedef uint8_t ddsComparitor_t;
#else // When using pin 11, we always want 8 bits #else // When using pin 11, we always want 8 bits
#define COMPARATOR_BITS 8 #define COMPARATOR_BITS 8
typedef uint8_t ddsComparitor_t;
#endif #endif
// This is how often we'll perform a phase advance, as well as ADC sampling // 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) // expense of CPU time. It maxes out around 62000 (TBD)
// May be overridden in the sketch to improve performance // May be overridden in the sketch to improve performance
#ifndef DDS_REFCLK_DEFAULT #ifndef DDS_REFCLK_DEFAULT
#define DDS_REFCLK_DEFAULT 9600 #ifdef __SAMD21G18A__
#define DDS_REFCLK_DEFAULT 44100
#else
#define DDS_REFCLK_DEFAULT 9600
#endif
#endif #endif
// As each Arduino crystal is a little different, this can be fine tuned to // As each Arduino crystal is a little different, this can be fine tuned to
// provide more accurate frequencies. Adjustments in the range of hundreds // provide more accurate frequencies. Adjustments in the range of hundreds
// is a good start. // is a good start.
@ -61,7 +82,7 @@ typedef uint32_t ddsAccumulator_t;
#endif #endif
// Output some of the calculations and information about the DDS over serial // 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 // When defined, use the 1024 element sine lookup table. This improves phase
// accuracy, at the cost of more flash and CPU requirements. // accuracy, at the cost of more flash and CPU requirements.
@ -202,7 +223,7 @@ public:
return refclkOffset; return refclkOffset;
} }
uint8_t getDutyCycle(); ddsComparitor_t getDutyCycle();
// Set a scaling factor. To keep things quick, this is a power of 2 value. // 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. // Set it with 0 for lowest (which will be off), 8 is highest.
@ -222,7 +243,7 @@ private:
volatile ddsAccumulator_t stepRate; volatile ddsAccumulator_t stepRate;
ddsAccumulator_t refclk; ddsAccumulator_t refclk;
int16_t refclkOffset; int16_t refclkOffset;
static DDS *sDDS; //static _DDS *sDDS;
}; };
#endif /* _DDS_H_ */ #endif /* _DDS_H_ */