Problem with High Resolution Timer

Moderator: nferre

cledic
Posts: 2
Joined: Mon Jan 05, 2015 12:21 am

Problem with High Resolution Timer

Mon Jan 05, 2015 10:48 pm

Hello to all,
I have problems using high resolution timer on a SAMA5D3 Xplained compatible board [1].
I'm using kernel 3.10, hrt enabled, with dts configured for 7inch display. I'm cross compiling on a Ubuntu 13 PC.

I made a very simple kernel module [2] that toggle a pin each time is called.
Using a scope I can see that lowering the timer value below 60us, nothing change.
I need a timer every 14us but the scope always show a 60us square wave.

Where am I wrong with my code?
Can someone help me?

TIA
Regards

Clemente

[1] http://acmesystems.it/BERTA-A5-LCD
[2] https://github.com/cledic/Acqua_SAMA5D3 ... /mod_hrt.c
abelloni
Posts: 15
Joined: Sat May 03, 2014 7:34 pm

Re: Problem with High Resolution Timer

Sat Mar 07, 2015 2:41 am

14µs is really short. It is already quite good to be able to attain 60µs. You should probably configure a PWM or the TCB to do what you are trying to achieve.

If you really have to use a GPIO, then you'll probably have to use the FIQ:

http://free-electrons.com/blog/fiq-hand ... ux-kernel/

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