SVC Number

RE: SVC Number

Vidar Berg — Tue, 26 May 2020 06:17:06 GMT

I agree this is probably something we should have documented more clearly. I actually did not expect r0-r2 to get altered when SVC interrupt was forwarded through the Softdevice. Thanks for the update and good luck with your porting.

RE: SVC Number

BricoFlo — Mon, 25 May 2020 14:31:23 GMT

Okay, there is all i need to implement service call into my RTOS, thanks a lot, that's clear now !

I don't know if i missed something but maybe it should be written in the service call Api documentation ;)

Anyway, thanks !

RE: SVC Number

Vidar Berg — Mon, 25 May 2020 14:22:04 GMT

I did a quick test trying to use SVC in the app with the Softdevice enabled which you can see the result of below.

LR is the same, but r0-r2 are different. r0 matches the SVC number, r1 the SP, and r2 holds the address to the SVC_Handler() in the application.

RE: SVC Number

BricoFlo — Mon, 25 May 2020 08:36:34 GMT

That's what in needed to understand, the EXC_RETURN is not altered by softdevice or rewritten to match what should be without soft device, i'm right ?

RE: SVC Number

Vidar Berg — Mon, 25 May 2020 08:23:41 GMT

LR will contain one of the EXC_RETURN (ARM documentation) values when you execute code inside the SVC handler. This is not something that's specific to Nordic chips.

RE: SVC Number

BricoFlo — Fri, 22 May 2020 10:51:13 GMT

So i can read the link return register, it will point to my code and so i can read SVC number i called just like other cortex ? the return path of interrupt skip soft device if i understand well ?

RE: SVC Number

Vidar Berg — Fri, 22 May 2020 10:44:43 GMT

The app gets notified of the SVC through an interrupt regardless if the Softdevice is present or not. The difference is the SVC interrupt gets routed through the Softdevice first.

RE: SVC Number

BricoFlo — Fri, 22 May 2020 10:40:33 GMT

by a function parameter ? meaning that i have one parameter used for this, so not usable as other M4 ?

RE: SVC Number

Vidar Berg — Fri, 22 May 2020 10:37:22 GMT

It will be forwarded to the SVC_Handler in your application If the number was not in the Softdevice's SVC range.

RE: SVC Number

BricoFlo — Fri, 22 May 2020 10:34:47 GMT

I already read the Supervisor Call interface chapter of the SDK but for numbers not intercepted by Softdevice and redirected to my SVC handler, how can i get the SVC Number if available ?

RE: SVC Number

Vidar Berg — Fri, 22 May 2020 10:28:59 GMT

Hello,

All SVC numbers that the application uses to interface with the Softdevice are handled inside the Softdevice. The Softdevice uses a separate SW interrupts to notify the application of various Softdevice events.

This is explained in more detail in the "Supervisor call interface" chapter of the SDK documentation and the "Application programming interface" section in the SDS.

I would suggest taking a look at the Heart Rate Application with FreeRTOS example from the nRF5 SDK to maybe get an overview of what's required to use the Softdevice with an RTOS.