pwm_f

[andys]

Hello people,
I have a problem and I was wondering if you could help me.
I wrote this code for a pic 18f 4450 microcontroller. The problem is that with the order I give, the frequency to be 4Mhz/16 it should be 250Khz, instead it is 2,9 Khz.(I have 250Khz on the microchip’s board but only 2,9 Khz on breadboard) Do you have any idea what the problem might be?
What is more, do you know how I can use 5 pwm while the component has 4 channels?




#include <18F4550.h>
#device ADC=16
#USE delay(CLOCK=40000000)
#fuses HS,NOWDT,NOPROTECT,NOLVP

//#use delay(clock=40000000, crystal)
//long duty_cycle,period;







void main()
{
long adc_result;

setup_adc_ports(ALL_ANALOG);
setup_adc(ADC_CLOCK_div_16);
setup_ccp1(CCP_PWM);
setup_ccp2(CCP_PWM);
//setup_ccp3(CCP_PWM);
setup_timer_2(T2_DIV_BY_16, 255, 1);
WHILE (1)
{
set_adc_channel(0);
delay_ms(1);
adc_result=read_adc();
adc_result>>=6;


if (adc_result<255>255)&&(adc_result<511>511)&&(adc_result<767>767)output_high(PIN_B3); else output_low(PIN_B3);

set_pwm1_duty(adc_result);
set_pwm2_duty(adc_result);
//set_pwm3_duty(adc_result);
}
}

[sjbaxter]

Your clock is not set up correctly !!

[andys]

[Ttelmah]

The correct setting (assuming this is a crystal), is:

#USE delay(CLOCK=4000000)
#fuses XT,NOWDT,NOPROTECT,NOLVP

The frequency you will see, will be the master clock, divided by four, divided by 16, divided by 256.

The master clock is divided internally by 4, to give the frequency fed to the Timer2 prescaler. This prescaler you have then set to /16. You have then set timer2, to count 0 to 255, then reset.

Best Wishes

[Guest]