Question

Write a code to generate a 5 kHz signal using timer. Vary it's duty cycle. Don't use delay function.

using any language

Answer 1

#include <P32xxxx.h>

#include <math.h> // required to use the sine function

#define NUMPTS 64

int sine[NUMPTS], triangle[NUMPTS];

void initio(int freq) { // freq can be 5-6050 Hz

 TRISD = 0xFF00; // make the bottom 8 bits of PORT D outputs

 SPI2CONbits.ON = 0; // disable SPI to reset any previous state

 SPI2BRG = 9; // 1 MHz SPI clock

 SPI2CONbits.MSTEN = 1; // enable master mode

 SPI2CONbits.CKE = 1; // set clock-to-data timing

 SPI2CONbits.MODE16 = 1; // activate 16-bit mode

 SPI2CONbits.ON = 1; // turn SPI on

 TRISF = 0xFFFE; // make RF0 an output to control load and ce

 PORTFbits.RF0 = 1; // set RF0 = 1

 PR1 = (20e6/NUMPTS)/freq - 1; // set period register for desired wave

 // frequency

 T1CONbits.ON = 1; // turn Timer1 on

}

void initwavetables(void) {

 int i;

 for (i=0; i<NUMPTS; i++) {

 sine[i] = 2047*(sin(2*3.14159*i/NUMPTS) + 1); // 12-bit scale

 if (i<NUMPTS/2) triangle[i] = i*511/NUMPTS; // 8-bit scale

 else triangle[i] = 510-i*511/NUMPTS;

 }

}

void genwaves(void) {

 int i;

 while (1) {

 for (i=0; i<NUMPTS; i++) {

 IFS0bits.T1IF = 0; // clear timer overflow flag

 PORTFbits.RF0 = 1; // disable load while inputs are changing

 SPI2BUF = sine[i]; // send current points to the DACs

 PORTD = triangle[i];

 while (SPI2STATbits.SPIBUSY); // wait until transfer completes

 PORTFbits.RF0 = 0; // load new points into DACs

 while (!IFS0bits.T1IF); // wait until time to send next point

 }

 }

}

int main(void) {

 initio(5000);

 initwavetables();

 genwaves();

}

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