Device: AT91SAM7X256-EK
Problematic peripheral: PIT (Periodic Interval Timer)

I'm trying to set an interrupt that will execute an handler when CPIV (in PIT_PIIR register) reach PIV (in PIT_MR register).

The interrupt executes as expected, but that happens only once. The interrupt isn't executed more than once.

I enabled & configured the interrupt in AIC for SYSC (System Controller). Afterwards I initialized PIT and enabled interrupt for it.

I have no idea what to do...
I read the datasheet and couldn't figure out what's wrong.

Someone have any idea...?

Thanks in advance.

Best regards,
Dor.

hello,
does your software acknowledge the interrupt like this:


regards
gerhard

Hi gerhardf,

Yes, but now after I tried several ways I almost made it:

The interrupt works infinitely (which is what I tried to do, at least for now) but it seems that there is no interval between each interrupt, even though I set PIV to be 0xFFFFF (top value).

I'm using an about 18 MHZ oscillator.

Thus the interval must take about 0.91 sec to be executed again (when PIV=0xfffff).

I'm using the user interface (Leds) to indicate the proper work of PIT.

So in my case, the interrupts take ALL CPU time, while the rest of the program isn't being executed.


I think that maybe I didn't quite understand how to configure the interrupt to work well.
A working example would be much appreciated! If it's not possible, a list of action that I need to do would help as well.

Additional 2 questions:

1. Should I define a handler as such:
   
   Code:
   __irq void interrupt_handler_name_here() { /*...*/ }
   
   ?
   I think that my develop environment (and compiler...) is RealView. I'm using EDGE as IDE.
2. What action should I execute in the interrupt's handler function?
   As you said, I must read PITC_PIVR. That's all?

Sorry for all these questions, I'm new at this.

Thanks

Regards,
Dor.

hello,
attached you can find one of the older atmel-examples for the pit.
It's using iar workbench, but should be portable to keil/arm.

regards
gerhard

I saw the code and will be able to try it tomorrow.

Is the debug (called "DBGU") essential for the PIT to work?

no!

It works :)

I also cleared the interrupt before it was called, and read the PIVR register.

In addition, I prefixed the handler function with "__irq" as such:



And changed the Master clock to be the oscillator clock (instead of the PLL clock which was the initial configuration)

Thanks :)