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pwm pic problem

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neelam29

New Member
Dear all...
i want to design a ckt using pwm with 1HZ frequency and duty cycle 10% on pic 16 f690. i m posting this code please tell me wht changes to make for my requirement...
#include <pic.h>/* PIC Configuration Bit:
** INTIO - Using Internal RC No Clock
** WDTDIS - Wacthdog Timer Disable
** PWRTEN - Power Up Timer Enable
** MCLREN - Master Clear Enable
** UNPROTECT - Code Un-Protect
** UNPROTECT - Data EEPROM Read Un-Protect
** BORDIS - Borwn Out Detect Disable
** IESODIS - Internal External Switch Over Mode Disable
** FCMDIS - Monitor Clock Fail Safe Disable
*/
__CONFIG(INTIO & WDTDIS & PWRTEN & MCLREN & UNPROTECT \
& UNPROTECT & BORDIS & IESODIS & FCMDIS);// Using Internal Clock of 8 Mhz
#define FOSC 8000000L// Delay Function
#define _delay_us(x) { unsigned char us; \
us = (x)/(12000000/FOSC)|1; \
while(--us != 0) continue; }void _delay_ms(unsigned int ms)
{
unsigned char i;
do {
i = 4;
do {
_delay_us(164);
} while(--i);
} while(--ms);
}void main(void)
{
unsigned int ipwm;
unsigned char state; OSCCON=0x70; // Select 8 Mhz internal clock TRISC = 0x00; // Set All on PORTC as Output
ANSEL = 0x00; // Set PORT AN0 to AN7 digital I/O
ANSELH = 0x00; // Set PORT AN8 to AN11 as Digital I/O
PORTC = 0x00; // Turn Off all PORTC /* Init PWM for Single Output */
CCP1CON=0b00001100; // Single PWM mode; P1A, P1C active-low; P1B, P1D active-low
CCPR1L=0; // Start with zero Duty Cycle T2CON=0b00000101; // Postscaler: 1:1, Timer2=On, Prescaller = 1:4
PR2=0x65; // Frequency: 4.90 KHz
TMR2=0; // Start with zero Counter

PSTRCON=0b00000100; // Enable Pulse Steering on P1C (RC3)
state=0; // Start with state 1 for(;;) {
ipwm=0;
while (ipwm < 255) {
CCPR1L=++ipwm;
_delay_ms(5); // Delay 5 millisecond
}

ipwm=0xff;
while (ipwm > 0) {
CCPR1L=--ipwm;
_delay_ms(5); // Delay 5 millisecond
}

_delay_ms(100); // Delay 100 millisecond if (state == 0) {
state=1;
PSTRCON=0b00001000; // Enable Pulse Steering on P1D (RC2)
} else if (state == 1) {
state=2;
PSTRCON=0b00001100; // Enable Pulse Steering on P1C and P1D (RC3 and RC2)
} else {
state=0;
PSTRCON=0b00000100; // Enable Pulse Steering on P1C (RC3)
}
}
}

thanku ...my doubt is how can pr2 value be changed cause its only 8 bit reg..i want more....
 
Last edited:
Looking at the data sheet will tell you that slapping a 20Mhz Osc on will get the bit resolution you want. An alternate plan, is to use a device that that has a Power Control PWM module. So a device like a 18f1330, 18fXX31, and others, have up to 14 bits resolution at low clock rates and frequencies.
 
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