Re: [ECOS] Use of IRQ on ARM

[Andrew Lunn <andrew at lunn dot ch>]

On Fri, Feb 24, 2006 at 03:18:43PM -0500, Francesco Regazzoni wrote:
> Hi,
> 
> I have one questions about attaching an handler for the IRQ generated by
> an ARM simulator.
> 
> I generate my eCos using:
> ecosconfig new integrator_arm9
> ecosconfig add posix
> 
> 
> 
> Then in my main.c I added this:
> 
> static cyg_interrupt int1;
> static cyg_handle_t int1_handle;
> int initInterruptHandler(void) {
>         cyg_vector_t int1_vector = CYGNUM_HAL_VECTOR_IRQ;
>         cyg_priority_t int1_priority = 0;
> 
>         cyg_interrupt_create (
>                 int1_vector,
>                 int1_priority,
>                 0,
>                 &MyHandler,
>                 NULL,
>                 &int1_handle,
>                 &int1);
> 
>         cyg_interrupt_attach (int1_handle);
>         cyg_interrupt_unmask (int1_vector);
>         cyg_interrupt_enable();
> }
> 
> 
> and I call it here:
> 
> int main(int argc, char **argv)
> {
> 	initInterruptHandler();
> 	while (1) {}
> }
> 
> 
> I was expecting to see my MyHandler being called when IRQ is raised, but
> when the pin of the CPU is up, I don't see my function being executed.
> 
> 
> Am I missing something?

The ARM processor only has two interrupts, IRQ and FIQ. So most chips
contain the "Advanced Interrupt Controller". This multiplexes many
interrupt sources onto the IRQ. See hal_platform_ints.h for a list of
these interrupts. cyg_interrupt_create() installs an interrupt handler
for one of these multiplex interrupts.

If you really want to install a handler for the IRQ, you need to use
the function cyg_interrupt_set_vsr(). Note that the function you
register must be a real interrupt handler, ie it must take care to not
destroy any registers. This means you will need to write it in
assembly language.

        Andrew

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