# pwm problem in mikroC -pic- [closed]

i am trying to do an simple PWM example in mikroC program using ISIS simulator for pic16f877a and i used the code in the program help and it didnt work

for(;;)
{
Pwm_Init(5000);
pwm_start();
delay_ms(500);
}


## closed as not a real question by Olin Lathrop, Leon Heller, stevenvh, Oli Glaser, W5VO♦Oct 7 '12 at 22:59

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. If this question can be reworded to fit the rules in the help center, please edit the question.

• There is too little to go on here - is this the whole of your code? How didn't it work? What is the error message? – Oli Glaser Oct 7 '12 at 21:04
• "Didn't work" is a useless description. – Olin Lathrop Oct 7 '12 at 21:12
• i think this the code used to start the pwm in mikroC i want to use pwm in a project but first i need to see how it works first and make sure that it works – alone Oct 8 '12 at 16:24
• it "didnt work" there is no errors in compiling but the problem that it do not work in the simulation ....i am sorry for being not clear in my question ..:) – alone Oct 8 '12 at 16:46

PWM needs at least 2 parameters. You only supply the 5000, which will probably be the frequency, but what about the duty cycle? If you don't initialize that and it defaults to 0 or 100 %, then you won't see anything.

edit
It appears you have to call the function Pwm_Change_Duty() with a value between 0 (minimum) and 255 (maximum) to set the duty cycle.
end of edit

Most microcontrollers with PWM will have more than 1 PWM channel, so you'll have to tell the program which channel you want to use as well.

Also, I don't know what Pwm_Init() and Pwm_start() do exactly, but normally they should be outside your main loop. Now you're executing them again and again. IMO should be

Pwm_Init(5000);
pwm_start();
for(;;)
{
delay_ms(500);
},


and then the delay() serves no function, so that you can omit it:

Pwm_Init(5000);
pwm_start();
for(;;)
{
}.

• ok i am just asking.... this is the code i saw in the help i used the code pwm_change_duty(value) and it didnt work so i think there is another thing to do so the pwm work on the ISIS – alone Oct 8 '12 at 16:16
• @alone - but have tried the Pwm_Change_Duty() I mention in my answer? And you also haven't answered Oli's question: what does "doesn't work" mean? What do you observe? If you can add details to the question it may be reopened. – stevenvh Oct 8 '12 at 16:22
• of course .... the code compile very will and there is no error in compiling but in the simulation it do not work thats my problem – alone Oct 8 '12 at 16:27