Elmi
Posts: 14
Joined: Fri Nov 27, 2015 6:21 am

Fast timer interrupt?

Sun May 20, 2018 9:08 am

Hi,

I know this is not a bare-metal question, but for me it seems this board fits best - feel free to move this thread when there is a better location.

I want to set-up a timer-interrupt which calls an IRQ with a frequency of at least 2 MHz to do some stuff regularly. The timers of the SoC seem to be capable of doing something like this. But: I do not have a bare metal application but I'm running Linux. I have two SoC-cores separated and can use one to exclusively do work qith this timer and to call my interrupt service routine.

I assume this IRQ-thingy can be done only for a kernel module. So my question: how can this be done exactly? Is it possible to use one of these fast timers to call an ISR with such a high frequency? If yes: any hints/ideas/resources that describe the procedure?

Thanks :-)

LdB
Posts: 755
Joined: Wed Dec 07, 2016 2:29 pm

Re: Fast timer interrupt?

Sun May 20, 2018 12:20 pm

Okay as a guide under Raspbian I believe the FIQ response time is 1 microsecond on a Pi1 down to around 500 nanoseconds on a Pi2 or Pi3.

There is a RealTime Kernel that has been done for Raspbian in which the response times are down as low as 91ns
https://medium.com/@metebalci/latency-o ... 9c20704495

You would be better discussing it in this thread with people who use that RT-kernel
viewtopic.php?f=29&t=206750

Elmi
Posts: 14
Joined: Fri Nov 27, 2015 6:21 am

Re: Fast timer interrupt?

Sun May 20, 2018 1:47 pm

Great - thanks!

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