Re: [Gumstix-users] GPIO question

[Frenzel, T. <Tor...@en...>]

The MUX syntax is actually quite simple, and it is explained at the top of
the header file (at least it is in the U-Boot I use...).

(IDIS | PTD | DIS | M4) for example means:

IDIS: Input disabled
PTD: Pull-type down
DIS: Pull disabled
M4: Multiplexing mode 4

To understand the multiplexing modes, you should look at TI's documentation
for the OMAP3530. Try http://www.ti.com/lit/gpn/omap3530 it should be the
link to the datasheet where everything is explained.

Regards,

Torben Frenzel

-----Ursprüngliche Nachricht-----
Von: Markus Svilans [mailto:msv...@ae...] 
Gesendet: Mittwoch, 8. September 2010 06:19
An: General mailing list for gumstix users.
Betreff: [Gumstix-users] GPIO question

Dear gumstix-users,

For an application, I would like to re-purpose some GPIOs on the Gumstix
Overo Air. The Overo Air will be mounted on a custom expansion board,
similar to a Tobi.

I've researched the GPIO documentation here:
http://www.gumstix.net/wiki/index.php?title=GPIO

I have located the files overo.h and mux.h in the U-Boot code.

Based on the code, such as overo.h line 124, I gather that manually
controlled GPIO lines have M4, whatever that is, and lines used by system
peripherals all seem to have M0 or M1.

124:    MUX_VAL(CP(GPMC_NCS3),        (IEN  | PTU | EN  | M4)) /*GPIO_54*/\

(What are M0, M1 and M4? I can see they are defined in mux.h, but there is
no explanation on what they mean.)

Altogether, I'm a bit lost, and don't know where to begin. Essentially I
would like to have manual control over the following GPIO lines, using the
command line method outlined on the Gumstix Wiki:

GPIO18_MMC3_D0        output
GPIO19_MMC3_D1        output
GPIO20_MMC3_D2        input
GPIO17_MMC3_D3        input
GPIO150_MMC3_WP        input
GPIO14_MMC3_DAT4        output
GPIO23_MMC3_DAT5        output
GPIO12_MMC3_CLK        output
GPIO22_MMC3_DAT6        output
GPIO114_SPI1_NIRQ        output
GPIO175_SPI1_CS1        input

Can someone help me get started in the right direction? Sample code or some
kind of recipe would be great.
Perhaps there are other GPIO lines, more suited to manual control?

Many thanks,
Markus.


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