GPIOlib: Difference between revisions
From ArmadeusWiki
(creation) |
(→Usage) |
||
| Line 19: | Line 19: | ||
==Usage== | ==Usage== | ||
* Find | ===Blink APFxxDev i.MX LED=== | ||
* Find the GPIO number connected to the LED, eg: | |||
** for APF27Dev: '''PF14 ->''' PortF (n°6) pin 14 -> (6-1)*32 + 14 -> GPIO n°'''174''' | |||
** for APF51Dev: GPIO1_2 -> Port 1 pin 2 -> GPIO n° 2 | |||
* Define envt variable (for portability): | |||
<pre class="apf"> | |||
# export LED=174 (APF27Dev) | |||
or | |||
# export LED=2 (APF51Dev) | |||
</pre> | |||
* Ask kernel to export the GPIO: | * Ask kernel to export the GPIO: | ||
<pre class="apf"> | <pre class="apf"> | ||
# echo | # echo $LED > /sys/class/gpio/export | ||
</pre> | </pre> | ||
* Access functions are created: | * Access functions are created: | ||
<pre class="apf"> | <pre class="apf"> | ||
# ls /sys/class/gpio/ | # ls /sys/class/gpio/gpio$LED/ | ||
active_low edge subsystem value | active_low edge subsystem value | ||
direction power uevent | direction power uevent | ||
| Line 32: | Line 41: | ||
* Check GPIO direction and put in output: | * Check GPIO direction and put in output: | ||
<pre class="apf"> | <pre class="apf"> | ||
# cat /sys/class/gpio/ | # cat /sys/class/gpio/gpio$LED/direction | ||
in | in | ||
# echo out > /sys/class/gpio/ | # echo out > /sys/class/gpio/gpio$LED/direction | ||
# cat /sys/class/gpio/ | # cat /sys/class/gpio/gpio$LED/direction | ||
out | out | ||
</pre> | </pre> | ||
* Play with GPIO value: | * Play with GPIO value to blink LED: | ||
<pre class="apf"> | |||
# echo 1 > /sys/class/gpio/gpio$LED/value | |||
# echo 0 > /sys/class/gpio/gpio$LED/value | |||
</pre> | |||
===Get APFxxDev i.MX switch status=== | |||
* Find the GPIO number connected to the switch, eg: | |||
** for APF27Dev: '''PF15 ->''' PortF (n°6) pin 15 -> (6-1)*32 + 15 -> '''GPIO n°175''' | |||
** for APF51Dev: '''GPIO1_3''' -> Port 1 pin 3 -> '''GPIO n°3''' ((1-1)*32 + 3) | |||
* Define envt variable (for portability): | |||
<pre class="apf"> | |||
# export LED=175 (APF27Dev) | |||
or | |||
# export LED=3 (APF51Dev) | |||
</pre> | |||
* Ask kernel to export the GPIO: | |||
<pre class="apf"> | |||
# echo $LED > /sys/class/gpio/export | |||
</pre> | |||
* Access functions are created: | |||
<pre class="apf"> | |||
# ls /sys/class/gpio/gpio$LED/ | |||
active_low edge subsystem value | |||
direction power uevent | |||
</pre> | |||
* Check GPIO direction and put in output: | |||
<pre class="apf"> | |||
# cat /sys/class/gpio/gpio$LED/direction | |||
in | |||
</pre> | |||
* Get switch status: | |||
<pre class="apf"> | <pre class="apf"> | ||
# | # cat /sys/class/gpio/gpio$LED/value | ||
# | 1 (released) | ||
... | |||
# cat /sys/class/gpio/gpio$LED/value | |||
0 (pressed) | |||
</pre> | </pre> | ||
==Links== | ==Links== | ||
* http://www.kernel.org/doc/Documentation/gpio.txt | * http://www.kernel.org/doc/Documentation/gpio.txt | ||
Revision as of 12:12, 2 May 2011
Page under construction...
Informations on this page are not guaranteed !!
With recent Linux kernel (> 2.6.3x), there is an abstraction layer meant to ease GPIO usage: gpiolib. We will explain here how to use it.
Installation
- If not already done:
$ make linux26-menuconfig
Device Drivers --->
-*- GPIO Support --->
[*] /sys/class/gpio/... (sysfs interface)
$ make
- reflash your kernel (if needed)
Usage
Blink APFxxDev i.MX LED
- Find the GPIO number connected to the LED, eg:
- for APF27Dev: PF14 -> PortF (n°6) pin 14 -> (6-1)*32 + 14 -> GPIO n°174
- for APF51Dev: GPIO1_2 -> Port 1 pin 2 -> GPIO n° 2
- Define envt variable (for portability):
# export LED=174 (APF27Dev) or # export LED=2 (APF51Dev)
- Ask kernel to export the GPIO:
# echo $LED > /sys/class/gpio/export
- Access functions are created:
# ls /sys/class/gpio/gpio$LED/ active_low edge subsystem value direction power uevent
- Check GPIO direction and put in output:
# cat /sys/class/gpio/gpio$LED/direction in # echo out > /sys/class/gpio/gpio$LED/direction # cat /sys/class/gpio/gpio$LED/direction out
- Play with GPIO value to blink LED:
# echo 1 > /sys/class/gpio/gpio$LED/value # echo 0 > /sys/class/gpio/gpio$LED/value
Get APFxxDev i.MX switch status
- Find the GPIO number connected to the switch, eg:
- for APF27Dev: PF15 -> PortF (n°6) pin 15 -> (6-1)*32 + 15 -> GPIO n°175
- for APF51Dev: GPIO1_3 -> Port 1 pin 3 -> GPIO n°3 ((1-1)*32 + 3)
- Define envt variable (for portability):
# export LED=175 (APF27Dev) or # export LED=3 (APF51Dev)
- Ask kernel to export the GPIO:
# echo $LED > /sys/class/gpio/export
- Access functions are created:
# ls /sys/class/gpio/gpio$LED/ active_low edge subsystem value direction power uevent
- Check GPIO direction and put in output:
# cat /sys/class/gpio/gpio$LED/direction in
- Get switch status:
# cat /sys/class/gpio/gpio$LED/value 1 (released) ... # cat /sys/class/gpio/gpio$LED/value 0 (pressed)
