how to implement v/f in arduino uno

/******************************************************************
* DDS-sinewave - 3phase
*
******************************************************************/


#include "avr/pgmspace.h"
#include "avr/io.h"
PROGMEM prog_uchar sine256[] =
{
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))
#define PWM_OUT_1 11 // PWM output on pin 11
#define PWM_OUT_2 10 // PWM output on pin 10
#define PWM_OUT_3 9 // PWM output on pin 9
#define LED_PIN 13 // LED status on pin 13
#define TEST_PIN 7 // Scope trigger on pin 7
#define POTEN_IN 0 // Potentiometer on pin 0
#define OFFSET_1 85 // Offset for second-phase
#define 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(void)
{
// 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
}

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