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A small Guy
Guest
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| Trouble setting up PWM on 16F684 |
 Posted: Sun Mar 08, 2009 1:23 pm |
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Hy to all,
I'm puzzled, i can't make run the PWM on the 16F684.
The PIN is CCP1, port C5, PIN #5, clock is 8Mhz, PWM freq is 5Khz:
| Code: |
setup_timer_2(T2_DIV_BY_4, 99, 1);
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And the simple program, just fading in/out a LED, is:
| Code: |
#include "C:\Documents and Settings\camp0s\Desktop\PIC\test\main.h"
long value=0;
void main()
{
setup_adc_ports(NO_ANALOGS|VSS_VDD);
setup_adc(ADC_OFF);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DIV_BY_4,99,1);
setup_ccp1(CCP_PWM);
//set_pwm1_duty(200); //0..200
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
setup_oscillator(OSC_8MHZ);
while (true)
{
for (value=155;value<=200;value++)
{
set_pwm1_duty(value); //value must be long
delay_ms(25);
}
delay_ms(100);
for (value=199;value>=156;value--)
{
set_pwm1_duty(value); //value must be long
delay_ms(25);
}
}
}
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The LED is on pin #5 but it stays full on for all time, and i cannot see any frequency out of the pin.. where could be the mistake?
Tnx. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun Mar 08, 2009 1:55 pm |
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1. Post the main.h file.
2. Post your compiler version.
3. Have you ever made anything work with this PIC ? For example,
can you blink an LED ? |
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Guest
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| Posted: Sun Mar 08, 2009 2:43 pm |
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Hi!
It looks it was kind of false alarm. The compiler is 4.084 and the pic is working (not broken), the LED on/off works too.
Maybe i was hungry, after dinner, i double checked the setup and:
_ prescaler, timer2 and duty calculation where correct, but i missed the MAX value for the PWM which is 400 (5kHz, 8MHz clock), in the program i was doing up to 200
_ LED: i used a white led, bad, threshold voltage is rather high so i got full on, but full off for most of the time;
_ too bad, when i tried a fixed value it was high enough to light it.
_ too bad^2 when i tried the fading program the low threshold was too high again and i couldn't notice the dimming.
To get better debug i increased the delay_ms() between each step, removed the LED, downsized stepping to 10% increase/decrease at time and.. finally it worked!
One side note, while using the CCS setup wizard project, at the page labelled "other" where you setup the CCPX Settings functions there's a text saying "pulse width modulator output on pin C2", but for the 16f684, the correct pin is RC5.
Tnx. |
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Guest
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| Posted: Sun Mar 08, 2009 2:44 pm |
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Just forgot, anyway, main.h:
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#include <16F684.h>
#device adc=8
#FUSES NOWDT //No Watch Dog Timer
#FUSES INTRC_IO //Internal RC Osc, no CLKOUT
#FUSES NOPROTECT //Code not protected from reading
#FUSES NOBROWNOUT //No brownout reset
#FUSES NOMCLR //Master Clear pin used for I/O
#FUSES NOCPD //No EE protection
#FUSES PUT //Power Up Timer
#FUSES IESO //Internal External Switch Over mode enabled
#FUSES FCMEN //Fail-safe clock monitor enabled
#use delay(clock=8000000)
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Guest
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| Posted: Sun Mar 08, 2009 3:15 pm |
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Here again!
There's more!!
I found one more clue to why PWM was on it's own before, here's the code:
| Code: |
#include "C:\Documents and Settings\guest\Desktop\PIC\test\main.h"
#use fast_io (A)
//#use fast_io (C)
/*
#int_RA
void RA_isr(void)
{
delay_ms (50);
if (input(PIN_A0)==1) output_toggle(PIN_C3);
}*/
long value=0;
void main()
{
setup_adc_ports(NO_ANALOGS|VSS_VDD);
setup_adc(ADC_OFF);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DIV_BY_4,99,1);
setup_ccp1(CCP_PWM);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
set_tris_a (0x3F);
enable_interrupts(INT_RA);
enable_interrupts(GLOBAL);
setup_oscillator(OSC_8MHZ);
value=200;
set_pwm1_duty(value);
output_low(PIN_C3);
while (true)
{
delay_ms(1000);
}
}
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With this code (and the previous main.h) the PWM output is not working:
_ the output pin is fixed at 5V
_ there is no frequency signal on it
BUT, if you comment these two lines:
/*
enable_interrupts(INT_RA);
enable_interrupts(GLOBAL);
*/
PWM is working again:
_ current setup, value=200 gives Vout_Avg of 2.5V, 50% duty
_ i can find the 5KHz signal out of the PIC pin
So.. kind of bug or enabling interrupts arise problems?
Tnx. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun Mar 08, 2009 3:41 pm |
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| Quote: | /*
#int_RA
void RA_isr(void)
{
delay_ms (50);
if (input(PIN_A0)==1) output_toggle(PIN_C3);
}
*/
enable_interrupts(INT_RA);
enable_interrupts(GLOBAL);
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If you have the #int_ra interrupt service routine commented out (as
shown above), you must not enable interrupts. If you do, and you
get an INT_RA interrupt, the PIC will jump to the interrupt vector
address and there will be nothing there. The program will crash. |
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Guest
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| Posted: Sun Mar 08, 2009 4:47 pm |
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Uhm, this appears to work now, thanks for pointing me at the right direction! i was thinking that without stimulating port_a nothing could happen.
I'm just doing a small homework for school but I'm confused by all the implications of "touching this and not specifying that one" could generate..
I just attached 5 buttons (if pressed level goes up) to the port_a of the PIC and i wanted to modify the PWM like +10% at a time (and -10%) depending on the pressed buttons.
In theory a small and straightforward flowchart.. in reality a pain, cause nothing is going right, I'm messing with fast_io, i need debounce but cannot pause too much to fully read input and clear int vector, and it's already late in the night..
Last time i used a PIC i did it all in ASM, it was a nice propeller clock.. but definitely took too much time (but debug was way easier, just keep track of the bits); this time trying first C coding i found little frustrating to understand why it hang/problem that arise, kind of my errors accumulate with implicit restrictions made by few lines of code setup.
"I feel" C coding, especially in peripheral setup, should be restricted to two condition:
_ either ALL requirements are satisfied, so code is assembled
_ if one statement or logic block miss, halt or signal to the user of half-state of "the machine"
.. but, don't take it too much serious :|
Tnx again. |
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