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#include "avr/pgmspace.h"

#include "avr/io.h"



// Look Up table of a single sine period divied up into 256 values. Refer to PWM to sine.xls on how the values was calculated

const byte sine256[] PROGMEM  = {

  127, 130, 133, 136, 139, 143, 146, 149, 152, 155, 158, 161, 164, 167, 170, 173, 176, 178, 181, 184, 187, 190, 192, 195, 198, 200, 203, 205, 208, 210, 212, 215, 217, 219, 221, 223, 225, 227, 229, 231, 233, 234, 236, 238, 239, 240,

  242, 243, 244, 245, 247, 248, 249, 249, 250, 251, 252, 252, 253, 253, 253, 254, 254, 254, 254, 254, 254, 254, 253, 253, 253, 252, 252, 251, 250, 249, 249, 248, 247, 245, 244, 243, 242, 240, 239, 238, 236, 234, 233, 231, 229, 227, 225, 223,

  221, 219, 217, 215, 212, 210, 208, 205, 203, 200, 198, 195, 192, 190, 187, 184, 181, 178, 176, 173, 170, 167, 164, 161, 158, 155, 152, 149, 146, 143, 139, 136, 133, 130, 127, 124, 121, 118, 115, 111, 108, 105, 102, 99, 96, 93, 90, 87, 84, 81, 78,

  76, 73, 70, 67, 64, 62, 59, 56, 54, 51, 49, 46, 44, 42, 39, 37, 35, 33, 31, 29, 27, 25, 23, 21, 20, 18, 16, 15, 14, 12, 11, 10, 9, 7, 6, 5, 5, 4, 3, 2, 2, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 2, 2, 3, 4, 5, 5, 6, 7, 9, 10, 11, 12, 14, 15, 16, 18, 20, 21, 23, 25, 27, 29, 31,

  33, 35, 37, 39, 42, 44, 46, 49, 51, 54, 56, 59, 62, 64, 67, 70, 73, 76, 78, 81, 84, 87, 90, 93, 96, 99, 102, 105, 108, 111, 115, 118, 121, 124

};





#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))

#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))

int PWM_OUT_1 = 11; // PWM output on pin 11

int PWM_OUT_2 = 10; // PWM output on pin 10

int PWM_OUT_3 = 12; // PWM output on pin 9

int LED_PIN = 13; // LED status on pin 13

int TEST_PIN = 7; // Scope trigger on pin 7

int POTEN_IN = A0; // Potentiometer on pin 0

int OFFSET_1 = 85; // Offset for second-phase

int OFFSET_2 = 170; // Offset for third-phase

double dfreq;

const double refclk = 31376.6; // measured

const uint64_t twoTo32 = pow(2, 32); // compute value at startup and use as constant

// variables used inside interrupt service declared as voilatile

volatile uint8_t icnt; // var inside interrupt

volatile uint8_t icnt1; // var inside interrupt

volatile uint8_t c4ms; // counter incremented every 4ms

volatile uint32_t phase_accum; // pahse accumulator

volatile uint32_t tword_m; // dds tuning word m

//******************************************************************

void setup()

{

  pinMode(LED_PIN, OUTPUT); // sets the digital pin as output

  Serial.begin(115200); // connect to the serial port

  Serial.println("DDS Test");



  pinMode(TEST_PIN, OUTPUT); // sets the digital pin as output

  pinMode(PWM_OUT_1, OUTPUT); // PWM output / frequency output

  pinMode(PWM_OUT_2, OUTPUT); // PWM output / frequency output

  pinMode(PWM_OUT_3, OUTPUT); // PWM output / frequency output

  // Setup the timers

  setup_timer1();

  setup_timer2();

  // disable interrupts to avoid timing distortion

  cbi (TIMSK0, TOIE0); // disable Timer0 !!! delay() is now not available

  sbi (TIMSK2, TOIE2); // enable Timer2 Interrupt

  dfreq = 1000.0; // initial output frequency = 1000.0 Hz

  tword_m = twoTo32 * dfreq / refclk; // calulate DDS new tuning word

}

//******************************************************************

void loop()

{

  if (c4ms > 250) // timer / wait for a full second

  {

    c4ms = 0;

    dfreq = analogRead(POTEN_IN); // read Poti on analog pin 0 to adjust output frequency from 0..1023 Hz

    cbi (TIMSK2, TOIE2); // disble Timer2 Interrupt

    tword_m = twoTo32 * dfreq / refclk; // calulate DDS new tuning word

    sbi (TIMSK2, TOIE2); // enable Timer2 Interrupt

    Serial.print(dfreq);

    Serial.print(" ");

    Serial.println(tword_m);

  }

}

//******************************************************************

// timer1 setup

// set prscaler to 1, PWM mode to phase correct PWM, 16000000/512 = 31.25kHz clock

void setup_timer1(void)

{

  // Timer1 Clock Prescaler to : 1

  sbi (TCCR1B, CS10);

  cbi (TCCR1B, CS11);

  cbi (TCCR1B, CS12);

  // Timer0 PWM Mode set to Phase Correct PWM

  cbi (TCCR1A, COM1A0); // clear Compare Match

  sbi (TCCR1A, COM1A1);

  cbi (TCCR1A, COM1B0); // clear Compare Match

  sbi (TCCR1A, COM1B1);

  sbi (TCCR1A, WGM10); // Mode 1 / Phase Correct PWM

  cbi (TCCR1A, WGM11);

  cbi (TCCR1B, WGM12);

  cbi (TCCR1B, WGM13);

}



//******************************************************************

// timer2 setup

// set prscaler to 1, PWM mode to phase correct PWM, 16000000/512 = 31.25kHz clock

void setup_timer2()

{

  // Timer2 Clock Prescaler to : 1

  sbi (TCCR2B, CS20);

  cbi (TCCR2B, CS21);

  cbi (TCCR2B, CS22);

  // Timer2 PWM Mode set to Phase Correct PWM

  cbi (TCCR2A, COM2A0); // clear Compare Match

  sbi (TCCR2A, COM2A1);

  sbi (TCCR2A, WGM20); // Mode 1 / Phase Correct PWM

  cbi (TCCR2A, WGM21);

  cbi (TCCR2B, WGM22);

}

//******************************************************************

// Timer2 Interrupt Service at 31.25kHz = 32us

// this is the timebase REFCLOCK for the DDS generator

// FOUT = (M (REFCLK)) / (2 exp 32)

// runtime : 8 microseconds ( inclusive push and pop)

ISR(TIMER2_OVF_vect)

{

  sbi(PORTD, TEST_PIN); // Test / set PORTD,TEST_PIN high to observe timing with a oscope

  phase_accum += tword_m; // soft DDS, phase accu with 32 bits

  icnt = phase_accum >> 24; // use upper 8 bits for phase accu as frequency information

  OCR2A = pgm_read_byte_near(sine256 + icnt); // read value fron ROM sine table and send to PWM DAC

  OCR1A = pgm_read_byte_near(sine256 + (uint8_t)(icnt + OFFSET_1));

  OCR1B = pgm_read_byte_near(sine256 + (uint8_t)(icnt + OFFSET_2));

  if (icnt1++ == 125) // increment variable c4ms every 4 milliseconds

  {

    c4ms++;

    icnt1 = 0;

  }

  cbi(PORTD, TEST_PIN); // reset PORTD,TEST_PIN

}