which adc value to get corresponding output 50hz frequency of sine wave??

i wana to make an inverter by using aurdino uno has spwm pulse generator.

this is the program got from website. pls explain the program.

// A select button

include "avr/pgmspace.h"

// table of 256 sine values / one sine period / stored in flash memory 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))

int ledPin = 13; // LED pin 7 int testPin = 7; int t2Pin = 6; byte bb;

double dfreq; // const double refclk=31372.549; // =16MHz / 510 const double refclk=31376.6; // measured

// variables used inside interrupt service declared as voilatile volatile byte icnt; // var inside interrupt volatile byte icnt1; // var inside interrupt volatile byte c4ms; // counter incremented all 4ms volatile unsigned long phaccu; // pahse accumulator volatile unsigned long tword_m; // dds tuning word m

void setup() { pinMode(ledPin, OUTPUT); // sets the digital pin as output Serial.begin(115200); // connect to the serial port Serial.println("DDS Test");

pinMode(6, OUTPUT); // sets the digital pin as output pinMode(7, OUTPUT); // sets the digital pin as output pinMode(11, OUTPUT); // pin11= PWM output / frequency output

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.o Hz tword_m=pow(2,32)*dfreq/refclk; // calulate DDS new tuning word

} void loop() { while(1) { if (c4ms > 250) { // timer / wait fou a full second c4ms=0; dfreq=analogRead(0); // read Poti on analog pin 0 to adjust output frequency from 0..1023 Hz

cbi (TIMSK2,TOIE2); // disble Timer2 Interrupt tword_m=pow(2,32)*dfreq/refclk; // calulate DDS new tuning word sbi (TIMSK2,TOIE2); // enable Timer2 Interrupt

Serial.print(dfreq); Serial.print(" "); Serial.println(tword_m); }

sbi(PORTD,6); // Test / set PORTD,7 high to observe timing with a scope cbi(PORTD,6); // Test /reset PORTD,7 high to observe timing with a scope } } //****************************************************************** // timer2 setup // set prscaler to 1, PWM mode to phase correct PWM, 16000000/510 = 31372.55 Hz 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 31372,550 KHz = 32uSec // 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,7); // Test / set PORTD,7 high to observe timing with a oscope

phaccu=phaccu+tword_m; // soft DDS, phase accu with 32 bits icnt=phaccu >> 24; // use upper 8 bits for phase accu as frequency information // read value fron ROM sine table and send to PWM DAC OCR2A=pgm_read_byte_near(sine256 + icnt);

if(icnt1++ == 125) { // increment variable c4ms all 4 milliseconds c4ms++; icnt1=0; }

cbi(PORTD,7); // reset PORTD,7 }

Please go back and edit your posting to use code tags so that there is

// A select button

Then we can easily grab it and play...

sorry select button ??? what u mean ??

Hi

Please use code tags.. See section 7 http://forum.arduino.cc/index.php/topic,148850.0.html

Tom.... :)

That looks like reasonably well-commented code. What words or concepts are you having trouble with?