C515C + PWM

I tried Mr.Chris's program.. and the problem still there,
If I made the program as:

while(1) {
    delay(100);         /* delay ~100 msec */
    P1 ^= 0x04;         /* toggle P1.2    */
    }

It will make a delay and toggle P1.2

And if I made the program as:

    updateDC == 1
    dc = 75;
    while(1) {
    if (updateDC == 1) {
    updateDC = 0;
    SetDC(dc);
    }
  };

The result will be a PWM with a duty cycle of 75%

But when I put the program as:

 while(1) {
    delay(100);         /* delay ~100 msec */
    P1 ^= 0x04;         /* toggle P1.2    */

    if (updateDC == 1) {
      updateDC = 0;
      SetDC(dc);
    }
  };

!!!!

The pin will toggle and no PWM signal !!
What is the problem?!
please help

I tried Mr.Chris's program.. and the problem still there,
If I made the program as:

while(1) {
    delay(100);         /* delay ~100 msec */
    P1 ^= 0x04;         /* toggle P1.2    */
    }

It will make a delay and toggle P1.2

And if I made the program as:

    updateDC == 1
    dc = 75;
    while(1) {
    if (updateDC == 1) {
    updateDC = 0;
    SetDC(dc);
    }
  };

The result will be a PWM with a duty cycle of 75%

But when I put the program as:

 while(1) {
    delay(100);         /* delay ~100 msec */
    P1 ^= 0x04;         /* toggle P1.2    */

    if (updateDC == 1) {
      updateDC = 0;
      SetDC(dc);
    }
  };

!!!!

The pin will toggle and no PWM signal !!
What is the problem?!
please help

you present us with a ton of unknowns such as
SetDC(dc);
which nobody (but you) has any idea of what does.

If you want ANY precision in your PWM get out of main() use the T2 interrupt ISR.

You are fooling around with delays in main() written in C that a) may change any day (there is no restriction on how C is implemented and it often changes from release to release) and b) 'hangs' your processor and c) if e.g. an UART interrupt happes will change.

go cure your interruptifobia and then try again.

The pin will toggle and no PWM signal !!
if the pin toggles you have a PWM signal, maybe not the frequency or duty cycle you want, but you DO have a PWM signal.

Erik

This is dead simple if you do not try to be fancy here is some pseudocode

in main() where you find out what the PWM is to be you set two variables: Up and Down, Up being the number of T2 clocks you want the PWM output to be high and Down being the number of T2 clocks you want the PWM output to be low. For a contstant frequency Up plus Down must always be the same.

Then you have the variables High and Low High being (10000h minus Up) + fiddle and Low being (10000h minus Down) + fiddle. You also need a bit variable, let's call it On

then in the T2 ISR
stop the timer
if ON
-- clear On
-- set the timer value (TH and TL) to the value Low
-- clear the port pin
else
-- set On
-- set the timer value (TH and TL) to the value High
-- set the port pin
endif
start the timer
exit

fiddle above is the number of T2 clocks that would occur during ISR execution which you can calculate with "the bible" chapter 2. If you need ultimate precision code the T2 ISR in assembler so the time it takes will be constant.

Mr.Erik,

SetDC(dc); is the function that sets the amount of the duty cycle in % and Mr.Chris explained that before..
I am not looking for the accuracy of my PWM signal.. (Thanks to this forum) I already generated the PWM signal and its accuracy is accepted for me..

Now it is working "get out of main()", I made a function called pwm() out of the main and I call it when I need to change the duty cycle..
The program is the same as of Mr. Chris Wunderlich , but with making a call outside the main()

This happens with me,, and I wrote this to help others "if they are beginner as much as me"

Thank you all..thanks alot

your student,Ashraf

Now it is working "get out of main()", I made a function called pwm() out of the main and I call it when I need to change the duty cycle..

read the whole thing!!!!!

get out of main() use the T2 interrupt ISR

you will lose all precision etc the moment you start going beyond your simple "test code"

Erik

T0 and T2 are running from interrupts

fine, but that is not the issue

if the change of state of a PWM output is handled in the main erratic performance WILL (eventually) happen.

Erik

'eventually' because it may not happen in a small 'demo' that does nothing but PWM, but such a 'demo' will not be the final code.