SAM7S256 PIT Interrupt

SirBlack · **Joined:** Wed Aug 18, 2010 11:12 pm **Posts:** 21

Hello,
I am having a hard time getting the PIT to work on my SAM7S256. I want it to tick every 100µs.
PIT_PERIOD is defined to 100.
It compiles fine.
The toggleIO Function works.

But there is nothing toggeling on BIT31.

Hope you can help me out.

Thanks

Code:

void ISR_PIT(void){
    toggleIO(AT91C_BASE_PIOA, BIT31);
    AT91F_PIO_ClearOutput(AT91C_BASE_PIOA, (1<<17)); //LED is low active
    int dummy =  AT91F_PITGetPIVR(AT91C_BASE_PITC);
    dummy = dummy;
    AT91F_AIC_AcknowledgeIt(AT91C_BASE_AIC);
}

int main(){
 /**** Periodic Interval Timer - Interrupt every 100µs ****/


        AT91F_PITInit(AT91C_BASE_PITC, PIT_PERIOD, 48); //100 uSek, 48Mhz

        // Configure interrupt on PIT
        AT91F_AIC_DisableIt(AT91C_BASE_AIC, AT91C_ID_SYS);
        AT91F_AIC_ConfigureIt(AT91C_BASE_AIC, AT91C_ID_SYS, PIT_INT_LEVEL, AT91C_AIC_SRCTYPE_INT_HIGH_LEVEL, ISR_PIT);
        AT91F_PITC_CfgPMC();
        AT91F_AIC_EnableIt(AT91C_BASE_AIC, AT91C_ID_SYS);

        AT91F_PITEnableInt(AT91C_BASE_PITC);

return 0;
}

dfridley · **Joined:** Thu Feb 25, 2010 5:02 pm **Posts:** 88

Hello -

In your main() it looks like your program ends after initializing the PIT. Did you forget to add a loop?

AT91F_PITEnableInt(AT91C_BASE_PITC);
while(1) {
;
}
return 0;

Regards,

SirBlack · **Joined:** Wed Aug 18, 2010 11:12 pm **Posts:** 21

No, its there. I just forgot to past it here. Sorry.

I have read, that my interrupt vector needs to be set to

Code:

ldr pc[pc,#-0xF20]

.

I am not sure where to put this information.
I use the OpenOCD Tool to flash the SAM7.
In my project I use some start upcode in Assembler, that was given in an example.
I wasn't to sure what this code was all about, so I just copied it.
Do I have to add this IRQ Vector somewhere in the Startup Code?

I tried the USART Receive Interrupt, too. It did not work as well.

Thanks for your reply.

Regards.

dfridley · **Joined:** Thu Feb 25, 2010 5:02 pm **Posts:** 88

Quote:

In my project I use some start upcode in Assembler, that was given in an example.

I'm not sure what startup code you are using. Did this come from the Atmel software package?

If not, you might want to start with the getting-started-project located in the AT91 software package or at least compare it to what you are using. (see http://www.atmel.com/dyn/resources/prod_documents/at91sam7s-ek.zip)

There are two files you should use or look at:
- board_cstartup*.s
- board_lowlevel.c

Regards,

SirBlack · **Joined:** Wed Aug 18, 2010 11:12 pm **Posts:** 21

I have compared the files.
I am not using the SAM7-EK. Therefore I use the startup-code given to my board.
It is written in assembler only. The IRQ Part is exactly the same. Also the low level init, that I am using is the same too. (Except for the "map to RAM" part).

Maybe I should try to use the "getting-started-project" to build my own project.
On the first glance it looks like a good starting point for a project.
The interrupt initialization in my first post is right?

SirBlack · **Joined:** Wed Aug 18, 2010 11:12 pm **Posts:** 21

So I have adapted the getting started project for my board and with the given interrupt definition.
But it is still not working.
Now I compile with the SAM7-EK makefile and the startup code given with the EK.

Any other ideas?
That's real frustrating.

SirBlack · **Joined:** Wed Aug 18, 2010 11:12 pm **Posts:** 21

Hello,
now it entered the ISR once.
The image was on the SRAM and it entered the ISR after a cpu reset initialized from OpenOCD.
But I am not able to replicate it?

Thats strange...

SAM7S256 PIT Interrupt

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