I found some information online about rebuilding u-boot.  Basically I just ran

$ bitbake u-boot
$ bitbake -c devshell u-boot

Which brought me into a development shell.  I modified ./board/omap3/overo/overo.h and added lines at the end of the file for the desired GPIO pins.  Save, exit, and bitbake continues through the rebuild.

Now I just need to find where the rebuilt u-boot went and how to actually put it on the board.  :)

On Tue, Dec 22, 2009 at 10:20 AM, <coderdrone@gmail.com> wrote:
Where do I get the sources for this?  When I search my entire overo-oe directory for overo.h, I find about 7 copies under overo-oe/tmp/(work or staging) but not the original file.  I do have an overo-oe/sources directory with a bunch of items, but nothing with uboot.


On Mon, Dec 21, 2009 at 7:53 PM, Steve Sakoman <sakoman@gmail.com> wrote:
On Mon, Dec 21, 2009 at 4:30 PM,  <coderdrone@gmail.com> wrote:
> Steve,
>
> Thank you for that information.  I'm not very familiar with u-boot, but I've
> seen environment variables in there before.  Can I assume that any of the
> multi-function pins (like 171 for example) on the 40-pin connector can be
> configured for one function or the other in u-boot?

Yes.  To be clear, though, this will require modifying the overo.h
file in the sources and rebuilding u-boot.

>  171 shouldn't be a
> problem since we won't be using a touchscreen controller in this system.
> I've never heard of Palo and Chestnut.  This board is Overo, or at least I
> believe Overo is the board name.  I'm still trying to get used to the naming
> conventions.

See the Gumstix website -- both Palo and Chestnut links can be found here:

http://gumstix.com/store/catalog/index.php?cPath=31

Steve

> On Mon, Dec 21, 2009 at 4:22 PM, Steve Sakoman <sakoman@gmail.com> wrote:
>>
>> On Mon, Dec 21, 2009 at 12:46 PM,  <coderdrone@gmail.com> wrote:
>> > Hello,
>> >
>> > I'm working on a C++ project to read button presses via GPIO pins from
>> > the
>> > Gumstix board and am running into some issues.  As I understand it,
>> > there
>> > are two different ways to read GPIO lines: 1.) reading through an API,
>> > or
>> > 2.) standard filesystem commands like cat and echo.  We are currently
>> > using
>> > filesystem commands.
>> >
>> > So far, I've just been trying to read the pins on the commandline via,
>> > for
>> > example, 'cat /sys/class/gpio/gpioN' where N is the GPIO number.  As I
>> > understand it, this gpio directory lists all the GPIO pins that have
>> > been
>> > 'exported' by the kernel to userspace.  However, if I export other
>> > GPIOs, I
>> > can't seem to successfully read them.  Is there a way to change the
>> > configuration of the kernel to make more GPIO pins available?  Could the
>> > kernel be reserving certain pins for other uses so I can't actually read
>> > button presses with them?  Am I just making this more complicated than
>> > it
>> > needs to be?
>> >
>> > The Gumstix board is mounted on a summit board, which has a 40-pin
>> > connector
>> > as referenced at
>> >
>> > http://www.gumstix.net/Hardware/view/I/O-connectors-cabling/Gumstix-Summit-board-40-pin-header-SV1/112.html.
>> >
>> > However, the GPIO pins listed on that chart don't match the GPIO pins
>> > that
>> > exist in /sys/class/gpio when I boot the system.  For example, GPIO114
>> > exists in the filesystem, but GPIO171 does not.  If I attach a button to
>> > the
>> > pins for GPIO114, the button appears to work (gpio114/value changes
>> > between
>> > 0 and 1).  I can 'echo 171 > export' to gain access to GPIO 171, but
>> > when I
>> > read the value of that pin via 'cat gpio171/value' it always stays at 0
>> > whether the attached button is pressed or not.
>> >
>> > Any thoughts?
>>
>> You will note that pin is labeled: GPIO171_SPI1_CLK
>>
>> This means it is a pin that can have 2 functions, either gpio_171 or
>> spi1_clk
>>
>> Since the Gumstix Palo and Chestnut boards use the spi bus for the
>> touchscreen controller, this pin is configured by u-boot for the spi
>> function and not the gpio function.  This is why you are not able to
>> use in successfully in that mode.
>>
>> If you want to use it in gpio mode you will need to modify the u-boot
>> pinmux setup.  Of course spi will no longer work then, so you should
>> make sure that whatever expansion board you are using doesn't require
>> spi.
>>
>> Steve
>>
>>
>> >
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