Re: [Gumstix-users] gpio on audiostix2

[Lee W. W. <lw...@ds...>]

Thanks. I also found this file ac97_patch.c, where the string to =
/proc/gpio is parsed.  Can I modify this to take in commands i created?

How do I compile this code?  After compiling what is the executable to =
copy to the gumstix?  Sorry for the dumb questions. I have never written =
a driver on Linux before.

Thanks & Regards,
Lee Wei Wei



-----Original Message-----
From: gum...@li... on behalf of Craig =
Hughes
Sent: Sat 10/20/2007 4:40 AM
To: General mailing list for gumstix users.
Subject: Re: [Gumstix-users] gpio on audiostix2
=20
On Oct 19, 2007, at 7:42 AM, Wei Wei wrote:

> Can somebody give me some directions as to how I can control the =20
> gpio on
> audiostix2 from a c program?
>
> I read from previous threads that you can control these lines from =20
> command
> using:
> echo "GPIO set in" > /proc/gpio/UCB1400-0-0.
>
> If this can be done, I believe there is also some way I can do the =20
> same
> thing in my c program, right?

You can open the /proc/gpio file in your C program and write to it, =20
then close it.  This won't be terribly fast, but will work great if =20
you're only occasionally switching the GPIOs (probably will max out =20
around a few hundred Hz though I've not tested it).  You'll actually =20
be limited speed-wise by the AC97 bus anyway, but might be able to =20
get somewhat faster by extending the UCB1400 driver to implement some =20
IOCTLs to let you switch the lines without having  to open/close a =20
file descriptor and go through the text parsing (simple though it is) =20
each time.

C

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