Letux Kernel


You are looking at an old revision of the page Devices-Overview. This revision was created by Nikolaus Schaller.

Table of Content

How to control Devices from user space (command line)

FIXME: update GPIO numbers!


This page lists the most important devices and drivers that are specific to this board. And how they can be accessed from user space.


Touch Screen

is mapped to


pen down status can be read through

cat /sys/devices/virtual/gpio/gpio157/value


can be selected by adding "omapdss.def_disp=lcd" to the boot args. This is done by "setenv defaultdisplay lcd" in our boot.scr.

?? how to choose from user space by ???

To disable/enable (power down/up) the LCD (state=0: off, state=1: on)

echo "$state" >/sys/devices/omapdss/display2/enabled


can be selected by adding "omapdss.def_disp=dvi" to the boot args

power (state=0: off, state=1: on)

echo $state >/sys/devices/virtual/gpio/gpio170/value


can be selected by adding "omapdss.def_disp=venc" to the boot args


power (state=0: off, state=1: on)

echo $state >/sys/devices/virtual/gpio/gpio145/value


power (state=0: off, state=1: on) - you may have to switch on/off/on to reset the GPS chip

echo $state >/sys/devices/virtual/gpio/gpio156/value

device file (use 9600 baud)

cat /dev/ttyS1

if the external antenna is active can be determined through

cat /sys/devices/virtual/gpio/gpio138/value  # 1=ext. ant.

AUX and Power button

FIXME: no longer available through direct GPIOs but input devices resp. tca6507 driver

button status can be read through

cat /sys/devices/virtual/gpio/gpio136/value  # 0=AUX pressed
cat /sys/devices/virtual/gpio/gpio137/value  # 0=POWER pressed

LEDs are switched through

    echo $state >/sys/devices/virtual/gpio/gpio70/value  # AUX - red
    echo $state >/sys/devices/virtual/gpio/gpio71/value  # AUX - green
    echo $state >/sys/devices/virtual/gpio/gpio78/value  # POWER - red
    echo $state >/sys/devices/virtual/gpio/gpio79/value  # POWER - green


Depending on the exact version of the board there may be I2C devices (besides the touch screen controller).

You should install http://packages.debian.org/de/lenny/i2c-tools resp. http://www.lm-sensors.org/wiki/I2CTools


There should be the following commands

  • i2cdetect
  • i2cdump
  • i2cget
  • i2cset

ADCs of the TPS65950

are available through /dev/twl4030-madc and the madc driver. See e.g. http://www.jumpnowtek.com/index.php?option=com_content&view=article&id=79&Itemid=91