Problem to control a PWM signal !

[bimo]

Greetings !
It's my first message in this forum and hope it won't be the last.
Well I have a little problem and I guess I can't find a best place than in here to expose it .
Can someone give a look at this sample code and tells me if i missed something ?

[asmboy]

right away i see:

1- unless you are declaring #use fastio() - then the set_tris statements are at best redundant .

2- you OUGHT to declare a safe default set_pwm1(xx) value
AS soon as you setup the pwm generator

3- place a solid upper bound of less than 1024 on ++duty

4- got pullups or pulldowns on port B pins you are testing??

5-have you considered
(a) how FAST the duty cycle can change when button pressed as coded??

(b) Button debounce and delay ??

address all these things and you are going to be a lot better off

[bimo]

thanks Asmboy for your answer

i was sure somebody would say that
well, know that i already cheked all theses theorys...otherwise even this code shoud make the signal to change :

while(1)
{
duty++;
set_pwm1_duty(duty);
delay_ms(100);
}

well ....nothing !
the signal don't change it's first random status..
as you can see no more readings on B port PINs and the problem continues, i even enabled the int_Timer2 and Global interrupts
..same thing !

i thought that my PIC could be damaged i changed it and the result was just the same

i forced a 0% duty cycle exactly after setting up the timer2

it's like if the "set_pwm1_duty(duty);" has no effect on the PIC but the "setup_timer_2" function does work, i changed the prescaler value and i got a new frequency and it was exact, but always with an uncontrolable random pulse with !

you know what i think....there is something wrong with this function "set_pwm1_duty(duty);" i can setup the timer but i can't control the pluse with could be something wrong with my compiler ?
i use an older version than the one on the CCS download section
version 3.2...is this one contains a bug or something....cause i found haundreds of examples for PWM and all of them use the same technique, there owners clames that it works fine for them, but why not for me ?

any ideas ?

thanks in advance

[asmboy]

do NOT enable the timer2 int - it is not involved here-
then try this snippet and forget about the buttons fro a moment:

[bimo]

I wrote exactly your snippet and nothing else.
Well...in the first start up i got a square signal of 19.53 KHz 50 % duty cycle.
But when i restarted my PIC again a got the same signal frequency but with a different duty cycle, i did it again and again and each time i got something different !
Certainly you're gonna say that I'm playing you...trust me !
I desoldered the 20 MHz crystal and it's capacitors and replaced it with a 16 MHz !
Guess what !....same thing !

Again with an 8 Mhz.....no change.

I can change the frequency but can't control the duty cycle !.... I even tested it with a PIC16F877A rather than the other PIC16F876A and i got absolutely the same result !

I really don't know what to do...tell me what is your compiler ?

This is driving me crazy !

[PCM programmer]

Have you ever made the PIC do anything, such as blink an LED ?
Is PWM the first thing you have ever tried ? If so, blink an LED first.
Try this program:

[bimo]

Well suspected that too but know that my PIC works fine
and this is my first test with the PWM modules but not the PICs ever.
I did many mini projects with 16f84 / 16f876 / 16f877.
This time my project is a DC motor speed controller.
The best way is to generate a PWM signal at a certain frequency and play with duty cycle to change the motor speed.
First I wrote a function that generates a PWM but the minimum delay was 1 ms and it generated a signal, and by changing it's duty cycle i could change the motor speed.
BUT !!!!

The frequency of this signal was very small and i could here the noisy tones coming form my motor.

The frequency was approximately 2 to 3 KHz.
By optimizing more and more my code i managed to make it up to 7 KHz, but the tones was always audible and even worse !!!
So I posted my problem in a Forum and the told me to use directly the PWM modules with which i can generate frequencies up to 200KHz...
So I did, to not risk my MOSFET to burn up I'm connecting the C2 PIN directly to my Oscilloscope (cause you know a startup with a 100% duty cycle may damage my MOSFET and it did indeed!).
Anyways, I don't use LEDs but I'm using a beeper or a buzzer that informs me if my PIC is working fine or not

At start up it makes 3 beeps and starts to loop (while(1)) and waiting for buttons on B0 and B1 to be pushed, once done it makes a 100 ms beep and increment/decrement the duty cycle and so on.

Here is my complete code:

[bimo]

Here.... I took the snippet above and compile it and it produced this LST file:

[Ttelmah]

Now, the code you post, won't compile (missing ';' on the end of the timer setup line), so is not what you are actually using. Not a good start...
I took:

[asmboy]

[bimo]

Before going to sleep i wanted to share this with you.
Finally i could make work, and you were right the problem came from my compiler i this it's buggy. Even after a reinstall the problem was the same so i change it to "PIC C Compiler CCS PCWHD 4 093" and with it and like magic all my problems disappeared and i managed to control my motor speed with PWM signal at 20 KHz frequency without any problem and all the noisy tones are gone !!
thanks every body and have a nice one

[asmboy]

so -OK -here is a fun google search...