Hello Rico,
I think it is my turn 
1.) you can find the definition of the configuration of the GPIO’s under:
/sys/kernel/debug/omap_mux/
for example if you want to learn the current configuration of the gpmc_ad6 pin
you should look for:
cat /sys/kernel/debug/omap_mux/gpmc_ad6
to make it availible for output you should write
echo 7 > /sys/kernel/debug/omap_mux/gpmc_ad6
and then if you want to use it you should export that pin.
echo 38 > /sys/class/gpio/export
after you exported it you can make it output
echo “out” > /sys/class/gpio/gpio38/direction
or input
echo “out” > /sys/class/gpio/gpio38/direction
you can change the output value as low:
echo “0” > /sys/class/gpio/gpio38/value
or as high
echo “0” > /sys/class/gpio/gpio38/value
you can find the manings of the numbers like 7 or 37 from the user guide of AM335X.
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As I know, normally first configuration is made by bootloader. (like mux.h) After bootloader, kernel changes the configuration as in the
/sys/kernel/debug/omap_mux/ directory. Whatever you write here will be executed with kernel.
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I think you should edit u-boot’s pin mux configurations and recompile it.
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As I know there is no major pin config changes on revisions of Beaglebone.
Regards
2012/12/3 Rico <rico.cadetg@gmail.com>
Hello
I have some questions concerning the GPIOs of the beaglebone:
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Is there somewhere a definition of the configuration of the GPIOs immediately at startup? (input / output / pullup / pulldown)
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When using Angstrom, does the kernel changes this configuration during boot?
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Is it possible to change the startup configuration of the GPIOs (before the kernel is loaded)?
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If its not possible to change the startup configuration, does the current configuration remain the same for further revisions of the beaglebone?
Thanks a lot for any help!
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