RC_PWM
Guest
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| Multiple duty cycles within one PWM. |
 Posted: Wed Apr 26, 2006 12:02 pm |
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Hello all,
I would like to generate a Variable PWM from 1 to 20Hz. When a period (.5-20mS) is selected, i would like to have 3 variable duty cycles inside this period. searching this forum i came up with code below ( i realize that this code only work to 2mS when duty_100=1023). When i turn OFF and ON CCPR1L inside duty cycle i can only see last duty cycle scope. Can i turn off and on CCPR1L of duty cycle?
Thank you,
RC_PWM
| Code: |
#include <16F877.h>
#device ADC=10
#device *=16
#use delay(clock=8000000)
#FUSES HS, NOWDT, NOPROTECT, BROWNOUT, NOCPD, PUT, NOLVP
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS, BRGH1OK)
char selection;
int16 duty_0=0, duty_12=128, duty_25=256, duty_50=512, duty_62=640,duty_75=786,duty_100=1023;
void main() {
setup_port_a(ALL_ANALOG);
enable_interrupts(GLOBAL);
output_low(PIN_C1); // Set CCP2 output low
output_low(PIN_C2); // Set CCP1 output low
setup_ccp1(CCP_PWM);
setup_ccp2(CCP_PWM);
setup_timer_2(T2_DIV_BY_16, 255, 1);
while(TRUE){
printf("\r\nFreq:\r\n");
printf(" 1) .5mS\r\n");
printf(" 2) 1mS\r\n");
printf(" 3) 2mS\r\n");
do {
selection=getc();
} while((selection<'1')||(selection>'3'));
switch(selection) {
case '1' :
set_pwm1_duty(duty_25); // 25% Duty Cycle
// Would like to turn off CCPR1L register
set_pwm1_duty(duty_50);
// Would like to turn off CCPR1L register again
set_pwm1_duty(duty_25);
break;
case '2' :
set_pwm2_duty(duty_62); // 62% Duty Cycle
set_pwm2_duty(duty_75); // 75% Duty Cycle
break;
case '3' :
set_pwm1_duty(duty_50); // 50% Duty Cycle
set_pwm2_duty(duty_50); // 20% Duty Cycle
break;
}
printf("%c\r\n",selection);
}
}
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| Code: |
case '1' :
set_pwm1_duty(duty_25); // 25% Duty Cycle
// When turn off CCPR1L register
set_pwm1_duty(duty_50);
// When turn off CCPR1L register again
set_pwm1_duty(duty_25);
break;
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