how to setup the SysTick handler

[oldoldman]

Hi guys,
I'm trying to setup SysTick handler on a picow board. What I konw roughly is

1. Setup the SysTick by programming the syst_csr/syst_rvr registers
2. Setup the IRQ handler by calling irq_set_enabled

When it comes to the irq_set_enabled, I have not idea of which irq number shoud I use. Any suggestion? Many thanks!

[lurch]

See here for a full list of interrupt numbers. (Or page 188 in https://datasheets.raspberrypi.com/pico/raspberry-pi-pico-c-sdk.pdf )

[oldoldman]

I've found from here that if I "override" the isr_systick in crt0.s, the SysTick will work. So I guess the irq number of SysTick is SIO_IRQ_PROC0. Is there any doc about this?

[kilograham]

So I guess the irq number of SysTick is SIO_IRQ_PROC0. Is there any doc about this?

No, this is not true. SysTick is not an interrupt, it is an exception

see here https://github.com/raspberrypi/pico-sdk/blob/master/src/rp2_common/hardware_exception/include/hardware/exception.h

[oldoldman]

But this is from the ARMv6-M arch doc

So SysTick is an interrupt. But it is not that important. And I must admit that what I guess is wrong. The exception number of SysTick is 15.

[kilograham]

Ha; from the same document ;-)

but as you say, it doesn't matter, however from an API perspective, the SDK treats it like an exception rather than an external interrupt

[oldoldman]

In my understanding of the ARM doc, SysTick is a kind of interrupt and interrupt is a kind of exception. So they are used interchangably.

[kilograham]

yeah, it is confusing, because it lives with the synchronous exceptions but acts like an interrupt, but doesn't have the regular NVIC controls like the rest of the interrupts. Anyways, my point was that the hardware_irq deals with the external interrupts (and has 0 based indexes for those)