Difference between revisions of "LED"
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With this "nand-disk" option selected, the led will blink each time nand access occur (try with ''sync'' command to see it blinking). | With this "nand-disk" option selected, the led will blink each time nand access occur (try with ''sync'' command to see it blinking). | ||
| + | |||
| + | === Switch led with user button === | ||
| + | |||
| + | It is possible to switch led state using the APF28Dev user button. This button is seen as gpio17 under Linux, then configure the led trigger as gpio : | ||
| + | |||
| + | <pre class="apf"> | ||
| + | # echo "gpio" > /sys/class/leds/apfdev:green:user/trigger | ||
| + | </pre> | ||
| + | |||
| + | New config files are available : | ||
| + | <pre class="apf"> | ||
| + | # ls /sys/class/leds/apfdev:green:user/ | ||
| + | brightness gpio power uevent | ||
| + | desired_brightness inverted subsystem | ||
| + | device max_brightness trigger | ||
| + | </pre> | ||
| + | |||
| + | Then the trigger gpio can be configured with ''gpio'' file : | ||
| + | |||
| + | <pre class="apf"> | ||
| + | # echo 17 > gpio | ||
| + | </pre> | ||
| + | |||
| + | Then pushing the user switch will now commute the LED state. | ||
=== Links === | === Links === | ||
See the kernel documentation [http://www.mjmwired.net/kernel/Documentation/leds-class.txt Documentation/leds-class.txt] for more information about this driver. | See the kernel documentation [http://www.mjmwired.net/kernel/Documentation/leds-class.txt Documentation/leds-class.txt] for more information about this driver. | ||
Revision as of 08:47, 10 July 2012
The linux LED driver class
On recent kernel, linux have a led driver. This led can be driven from /sys/class/leds/ directory.
For APF28Dev, the led is configurable under the directory :
# cd /sys/class/leds/apfdev:green:user
Blinking
The blinking style can be selected with trigger file. By defaut on APF28Dev, Heartbeat is selected :
# cat /sys/class/leds/apfdev:green:user/trigger none nand-disk mmc0 timer [heartbeat] backlight gpio default-on
Blinking style can be changed with echo command :
# echo "nand-disk" > /sys/class/leds/apfdev:green:user/trigger # cat /sys/class/leds/apfdev:green:user/trigger none [nand-disk] mmc0 timer heartbeat backlight gpio default-on
With this "nand-disk" option selected, the led will blink each time nand access occur (try with sync command to see it blinking).
Switch led with user button
It is possible to switch led state using the APF28Dev user button. This button is seen as gpio17 under Linux, then configure the led trigger as gpio :
# echo "gpio" > /sys/class/leds/apfdev:green:user/trigger
New config files are available :
# ls /sys/class/leds/apfdev:green:user/ brightness gpio power uevent desired_brightness inverted subsystem device max_brightness trigger
Then the trigger gpio can be configured with gpio file :
# echo 17 > gpio
Then pushing the user switch will now commute the LED state.
Links
See the kernel documentation Documentation/leds-class.txt for more information about this driver.
