Difference between revisions of "GPIOlib"
From ArmadeusWiki
(→Get APFxxDev i.MX switch status) |
(swith is on PF13 on APF27Dev) |
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===Get APFxxDev i.MX switch status=== | ===Get APFxxDev i.MX switch status=== | ||
* Find the GPIO number connected to the switch, eg: | * Find the GPIO number connected to the switch, eg: | ||
| − | ** for APF27Dev: ''' | + | ** for APF27Dev: '''PF13 ->''' PortF (n°6) pin 13 -> (6-1)*32 + 13 -> '''GPIO n°173''' |
** for APF51Dev: '''GPIO1_3''' -> Port 1 pin 3 -> '''GPIO n°3''' ((1-1)*32 + 3) | ** for APF51Dev: '''GPIO1_3''' -> Port 1 pin 3 -> '''GPIO n°3''' ((1-1)*32 + 3) | ||
* Define envt variable (for portability): | * Define envt variable (for portability): | ||
<pre class="apf"> | <pre class="apf"> | ||
| − | # export SWITCH= | + | # export SWITCH=173 (APF27Dev) |
or | or | ||
# export SWITCH=3 (APF51Dev) | # export SWITCH=3 (APF51Dev) | ||
Revision as of 14:41, 28 September 2011
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.
Contents
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: PF13 -> PortF (n°6) pin 13 -> (6-1)*32 + 13 -> GPIO n°173
- for APF51Dev: GPIO1_3 -> Port 1 pin 3 -> GPIO n°3 ((1-1)*32 + 3)
- Define envt variable (for portability):
# export SWITCH=173 (APF27Dev) or # export SWITCH=3 (APF51Dev)
- Ask kernel to export the GPIO:
# echo $SWITCH > /sys/class/gpio/export
- Access functions are created:
# ls /sys/class/gpio/gpio$SWITCH/ active_low edge subsystem value direction power uevent
- Check GPIO direction and put in output:
# cat /sys/class/gpio/gpio$SWITCH/direction in
- Get switch status:
# cat /sys/class/gpio/gpio$SWITCH/value 1 (released) ... # cat /sys/class/gpio/gpio$SWITCH/value 0 (pressed)
- Block until an event occur:
# cat /sys/class/gpio/gpio$SWITCH/edge none # echo both > /sys/class/gpio/gpio$SWITCH/edge
