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desert
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| 16F877A dual PWM signals problem |
 Posted: Fri Nov 28, 2008 10:12 am |
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hi all,
I try to generate 2 PWM signals at CCP1 & CCP2 via this simple code:
| Code: |
#include <16F877.h>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock = 4000000)
void main()
{
output_low(PIN_C1); // Set CCP2 output low
output_low(PIN_C2); // Set CCP1 output low
setup_ccp1(CCP_PWM); // Configure CCP1 as a PWM
setup_ccp2(CCP_PWM); // Configure CCP2 as a PWM
setup_timer_2(T2_DIV_BY_4, 124, 1); // 500 Hz
set_pwm1_duty(62); // 25% duty cycle on pin C2
set_pwm2_duty(62); // 50% duty cycle on pin C1
while(1); // Prevent PIC from going to sleep (Important !)
}
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Checking with a scope I get the PWM I want at CCP2 but no luck on CCP1 no matter what I do.
Could this be due to a faulty PIC?
Is there a way to rule out this option?
Thanks for the help,
Moshe |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Nov 28, 2008 11:47 am |
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| Are there any external components connected to the CCP1 pin (Pin C2) ? |
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desert
Guest
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| Posted: Fri Nov 28, 2008 3:36 pm |
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No, I disconnected everything so I can examine the micro controller alone.
it was originally connected to an H BRIDGE, but once it failed I started investigating.
the whole thing is mounted on a breadboard, but I sample the signal at the chip leg directly.
I find the chances of a hardware malfunction slim, but who knows...
any guesses or suggestions will be welcome.
thanks,
Moshe. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Nov 28, 2008 3:49 pm |
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| Quote: | | it was originally connected to an H BRIDGE, but once it failed |
Try a new PIC. |
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desert
Guest
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| Posted: Fri Nov 28, 2008 4:10 pm |
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| thanks for the help, I will try... |
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mlkushan
Joined: 16 Nov 2008
Posts: 22
Location: Sri Lanka
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| Sample code to generate two 40KHz PWM signals |
| Posted: Tue Dec 02, 2008 12:20 am |
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Hi,
Check this code segment. This works fine. Hope this will be helpful to you also. This generates 40KHz PWM signals on both PIN_C1 and PIN_C2.
Thanks.
| Code: |
#include <16F877A.h>
#device adc=8
#FUSES NOWDT //No Watch Dog Timer
#FUSES XT //Crystal osc <= 4mhz
#FUSES NOPUT //No Power Up Timer
#FUSES NOPROTECT //Code not protected from reading
#FUSES NODEBUG //No Debug mode for ICD
#FUSES NOBROWNOUT //No brownout reset
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NOCPD //No EE protection
#FUSES WRT_50% //Lower half of Program Memory is Write Protected
#use delay(clock=4000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)
void main()
{
int16 pwm_duty = 50; //to get a higher resolution
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_psp(PSP_DISABLED);
setup_spi(SPI_SS_DISABLED);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DIV_BY_1,24,1);
setup_ccp1(CCP_PWM);
setup_ccp2(CCP_PWM);
set_pwm1_duty(pwm_duty);
set_pwm2_duty(pwm_duty);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
// TODO: USER CODE!!
while(1);
}
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_________________
Kushan Sharma
mlkushan@gmail.com |
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