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From: Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP>
Newsgroups: comp.lang.ada
Subject: Re: Raspberry Pi, Real-Time and Ada
Date: Fri, 7 Feb 2014 00:26:07 +0000 (UTC)
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Date: 2014-02-07T00:26:07+00:00
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On 2014-02-06, Rego, P. <pvrego@gmail.com> wrote:
> Hello Simon,
> On Thursday, February 6, 2014 10:16:40 AM UTC-3, Simon Clubley wrote:
>> I've seen a number of reports about how much overhead there is within
>> Linux when trying to drive the GPIO lines on the Raspberry Pi, so I can
>> easily believe that it _is_ a OS level issue.
> Maybe these reports are available on the internet? It would be very good to take a look on them if possible. 
>
> Thanks.

I went back and had a closer look at this. (I've never actually used
Linux to drive GPIO lines as I either use a dedicated RTOS or just
write the code for bare metal mode).

It appears there are two ways of accessing the GPIO lines on the
Raspberry Pi under Linux: either via the /sys/class/gpio interface
or directly via memory mapped I/O.

It looks like all the types of performance comments I remember come
from the first access method and that you can get far better access
times using the second method.

Which method are you using ?

Simon.

-- 
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world