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PIT interrupt on SAM7

Posted by Nobody/Anonymous on December 22, 2006
I have been playing with the RTOS for a while using the AT91SAM7X256 and the atmel evaluation kit. However I got stuck and I hope you can give me a little help.

The problem is as follows:

The PIT is used for the vPortPreemptiveTick and the vPortNonPreemptiveTick functions. This Interruption is not only for the PIT but also for a couple of others peripherals (all using Interrupt source 1). What I want to do is to distinguish when is a PIT interrupt and when not. I think the modification should be in portasm.s79. In the entry point of the function vPortNonPreemptiveTick() we should ask what cause the interruption and then if wasn’t the PIT I call “do_something_is_noPIT()”. I try that with this following lines:





LDR R0, =auxiliar ; Atiende las interrupciones para el caso de que la interrupción sea diferente a la del PIT

mov lr, pc ; de ser diferente a la del PIT, subo una variable global y evito que se ejecuten las siguientes funciones


portSAVE_CONTEXT ; Save the context of the current task.

LDR R0, =vTaskIncrementTick ; Increment the tick count - this may wake a task.


auxiliar() is a function defined in port.c and will distinguish if it was PIT or other kind of interruption.

However it didn’t work! I try a couple of others things and neither they work.

I don’t know what else to try.

Thank you Very Much.

(Sorry for my English, I’m not a native English Speaker, I don’t even live in the US).

RE: PIT interrupt on SAM7

Posted by Richard on December 22, 2006
Not sure I follow the code exactly but it looks like you might be altering the registers BEFORE saving the context. The context must be saved before you look for the interrupt source, otherwise you will clobber the task state. It might be easier to do this from C code - so you have one interrupt entry point.

Take a look at the following threads on the same subject:



RE: PIT interrupt on SAM7

Posted by Nobody/Anonymous on January 9, 2007
I want and really would like to use C code. But I think IAR compiler does requires the tick to use an asm wrapper, so any changes should be made in the portasm.s79, Am I right?
Thank you,
Juan Baez

RE: PIT interrupt on SAM7

Posted by Nobody/Anonymous on January 9, 2007
I think the asm can remain the same. You need to look at prvSetupTimerInterrupt in port.c.

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