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Hi,

I'm trying to get a GPIO port working using both the echo commands from the shell and sysfs calls in my application but

both appear not to be toggling the actual GPIO pin on the 814x EVM. (GPIO 29 on TestPoint TP48).

root@dm814x-evm:~# echo 29 > /sys/class/gpio/export
root@dm814x-evm:~# ls /sys/class/gpio/gpio29
active_low edge subsystem value
direction power uevent
root@dm814x-evm:~# echo out > /sys/class/gpio/gpio29/direction
root@dm814x-evm:~# echo 1 > /sys/class/gpio/gpio29/value
root@dm814x-evm:~# echo 0 > /sys/class/gpio/gpio29/value
root@dm814x-evm:~# cat /sys/class/gpio/gpio29/value
0
root@dm814x-evm:~# echo 1 > /sys/class/gpio/gpio29/value
root@dm814x-evm:~# cat /sys/class/gpio/gpio29/value
1

I'm reading that the cause may be that the pin mux file is not set up for this pin to be GPIO.

If this is correct....Can someone provide me support on which file this is and where it is located..as well as some direction

on how to modify this file accordingly to change a pin to a GPIO. (ie GPIO 29)....

Also...after these changes are made, does the kenel need to be rebuilt and put on SD card ?

Does the board also require pull-ups or pull-downs to make the output change ?

If there are any pins on the 814 already configured for GPIO and would work out of the box , that would also save some effort

and could test those immediately....(please identify these if available)

I would appreciate any help in getting this to work...

Thanks

Hi Sid,

1. GPIO numbers start from 0, make sure that you are using the correct GPIO. From your logs I can say that GPIO values are toggling properly for GPIO29 means 30th GPIO pin.

2. Check the correct pinmux register, details can be found at "arch/arm/mach-omap2/mux814x.c".

Go through the corresponding PSP user guide for pinmux configuration. (http://processors.wiki.ti.com/index.php/TI81XX_PSP_User_Guide#DM814x.2FDM813x)

3. By using mux entries we can identify which pins are used for which purpose, by using debugfs

follow this post http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/168911.aspx

4. Debugfs entries will give the currently used GPIO values.

http://processors.wiki.ti.com/index.php/GPIO_Driver_Guide#Sysfs_control_-_User_Space

Also...after these changes are made, does the kenel need to be rebuilt and put on SD card ?

Anil: yes, kernel needs to be rebuild and put it in SD card.

Does the board also require pull-ups or pull-downs to make the output change ?

Anil: Not required

Regards

AnilKumar

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GPIO Not Working / Question on PinMux