PWM on 12f675

[Mick Kent]

I am trying to use timer0 and timer1 interrupts to generate a PWM signal on pin_A2. I used 3.169 and the wizard. My non working code follows:

#include <12F675.h>
#device adc=10
#use delay(clock=4000000)
#fuses INTRC, MCLR, BROWNOUT, NOWDT

#rom 0x3FF = {0x3470}
#define PWMout PIN_A2
#byte ANSEL=0x9f

int16 Pwidth;

#define Pwidth 35536

#int_TIMER1
void TIMER1_isr(void) {
Output_low(PWMout);
disable_interrupts(INT_TIMER1);
}

#int_TIMER0
void TIMER0_isr(void) {
Output_high(PWMout);
SET_TIMER1(Pwidth);
enable_interrupts(INT_TIMER1);
}

main()
{
ANSEL=11;
setup_adc_ports(AN1_ANALOG);
setup_adc(ADC_CLOCK_INTERNAL);
setup_counters(RTCC_INTERNAL,RTCC_DIV_64);
setup_timer_1(T1_INTERNAL|T1_DIV_BY_1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
enable_interrupts(INT_TIMER0);
enable_interrupts(global);
SET_TIMER0(0);
while(true);
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516840

[Neutone]

:=I am trying to use timer0 and timer1 interrupts to generate a PWM signal on pin_A2. I used 3.169 and the wizard. My non working code follows:
:=
:=#include <12F675.h>
:=#device adc=10
:=#use delay(clock=4000000)
:=#fuses INTRC, MCLR, BROWNOUT, NOWDT
:=
:=#rom 0x3FF = {0x3470}
:=#define PWMout PIN_A2
:=#byte ANSEL=0x9f
:=
:=int16 Pwidth;
:=
:=#define Pwidth 35536
:=
:=#int_TIMER1
:=void TIMER1_isr(void) {
:= Output_low(PWMout);
:= disable_interrupts(INT_TIMER1);
:= }
:=
:=#int_TIMER0
:=void TIMER0_isr(void) {
:= Output_high(PWMout);
:= SET_TIMER1(Pwidth);
:= enable_interrupts(INT_TIMER1);
:= }
:=
:=main()
:={
:= ANSEL=11;
:= setup_adc_ports(AN1_ANALOG);
:= setup_adc(ADC_CLOCK_INTERNAL);
:= setup_counters(RTCC_INTERNAL,RTCC_DIV_64);
:= setup_timer_1(T1_INTERNAL|T1_DIV_BY_1);
:= setup_comparator(NC_NC_NC_NC);
:= setup_vref(FALSE);
:= enable_interrupts(INT_TIMER0);
:= enable_interrupts(global);
:= SET_TIMER0(0);
:= while(true);



I perform PWM for motor control using this routine and only use the timer to regulate the loop period. I can assign values for on and off time. This is based on a loop that runs at a fixed speed. The bit test can be performed on a lesser bit to make it run faster. You could also run a variation of this code inside an interupt.

if(bit_test (PWM_Counter_lo++, 7))
{ PWM_Counter_lo = 0;
PWM_Counter++;
}
if(PWM_Cycle)
{ if(PWM_Counter > on_time)
{ PWM_Counter = 0;
PWM_Cycle = 0;
}
}
else
{ if(PWM_Counter > off_time)
{ PWM_Counter = 0;
PWM_Cycle = 1;
}
}
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516843