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