GPIO pullup/pulldown function

GoogleGroups
1

Hi,

I want to use one of the gpio pin from the expansion board of my beagle board xm. From /sys/class/gpio I can set successfully the “high or 1” and “low or 0” of VALUE (from a voltmeter it gives 1.8V for 1 and 0V for 0 form the pin) to a particular gpio given the DIRECTION is “out”, but when I set the DIRECTION to “in” the VALUE change to always “high or 1”. For my application I need to configure the GPIO with “in”=DIRECTION that will give “low/0”=VALUE so that when I apply 1.8V to that pin it will give “1”= Value. Probably, the reason why the GPIO pin gives always “1” during input state because it is currently set as pull-up function, Im wondering if there is a way to set it up to pulldown function.

Thanks,
Jeffrey

2

some gpio in expansion board may not be configured (by default) as
gpio. Look at the documentation to see the other functionality of the
said pin.

3

I have instructions on how to set the gpio pull up/down on a bone here [1]. It uses /sys/kernel/debug/omap_mux. I don’t know if that’s available on your xM. You may have to run

**mount -t debugfs debugfs /sys/kernel/debug/**

to get debug info to appear. omap_mux doesn’t appear on my xM.

–Mark

[1] http://elinux.org/EBC_Exercise_10_Flashing_an_LED#Reading_a_switch_-_bone