Revision as of 03:08, 18 September 2014

The Radxa Rock has 3 LEDs on board.

LED	GPIO ref.	GPIO number
Green	GPIO0_B4	172
Blue	GPIO0_B6	174
Red	GPIO0_B7	175

All are programmable using either LEDs class devices or GPIOs.

LEDs as class devices

On the latest kernel images (Ubuntu 14.04 server/desktop), the 3 LEDs are configured as LED class devices.

You can control them via /sys/class/leds/

Read the documentation for more information: https://www.kernel.org/doc/Documentation/leds/leds-class.txt

The default status of the three on board leds are:

Red: On when there is power
Green: Flash twice per second after the kernel booting, it's called heartbeat.
Blue: Flash when the uSD card is reading/writing.

You can change the behaviour of each LED by using the echo command on their trigger property.

   root@radxa:~ # echo none > /sys/class/leds/red/trigger
   root@radxa:~ # echo default-on > /sys/class/leds/red/trigger
   root@radxa:~ # echo timer > /sys/class/leds/red/trigger
   root@radxa:~ # echo heartbeat > /sys/class/leds/red/trigger

You can use cat on the trigger property to list all the available values.

   root@radxa:~ # cat /sys/class/leds/red/trigger
   none test_ac-online test_battery-charging-or-full test_battery-charging test_battery-full test_battery-charging-blink-full-solid mmc0 mmc1 timer [heartbeat] backlight gpio default-on sleep rfkill0

Here is the list of current triggers:

none
test_ac-online
test_battery-charging-or-full
test_battery-charging
test_battery-full
test_battery-charging-blink-full-solid
mmc0
mmc1
timer
heartbeat
backlight
gpio
default-on
sleep
rfkill0

@@ Line 61: / Line 61: @@
 * sleep
 * rfkill0
-= LEDs as GPIOs =
-On the previous kernel images, the LEDs can be controlled as GPIOs.
-Below is program in different languages to flash the green led on RR.
-== C ==
-<syntaxhighlight lang="c" enclose="div">
-#include <stdio.h>
-int main()
-{
-  FILE *fp = fopen("/sys/class/gpio/export", "w");
-  if( !fp )
-  {
-    printf("error open export file");
-    return 1;
-  }
-  fprintf(fp, "%d", 172);
-  fclose(fp);
-  fp = fopen("/sys/class/gpio/gpio175/direction", "w");
-  if( !fp )
-  {
-    printf("error open export file");
-    return 1;
-  }
-  fprintf(fp, "%s", "out");
-  fclose(fp);
-  fp = fopen("/sys/class/gpio/gpio175/value", "w");
-  if( !fp )
-  {
-    printf("error open export file");
-    return 1;
-  }
-  fprintf(fp, "%d", 1);
-}
-</syntaxhighlight>
-== Python ==
-<syntaxhighlight lang="python" enclose="div">
-import time
-def initpin(pinnum, mode):
-  '''
-  pinnum: pin number, eg. 172, 175 etc.
-  mode: pin mode, valid values: in or out
-  '''
-  with open('/sys/class/gpio/export', 'w') as f:
-    f.write(str(pinnum))
-  with open('/sys/class/gpio/gpio' + str(pinnum) + '/direction', 'w') as f:
-    f.write(str(mode))
-def setpin(pinnum, value):
-  with open('/sys/class/gpio/gpio' + str(pinnum) + '/value', 'w') as f:
-    f.write(str(value))
-if __name__ == '__main__':
-  initpin(172, 'out')
-  while True:
-    setpin(172, 0)
-    time.sleep(1)
-    setpin(172, 1)
-    time.sleep(1)
-</syntaxhighlight>
-== Shell ==
-<syntaxhighlight lang="bash" enclose="div">
-#!/bin/sh
-# enable the gpio 172 -> green led
-echo 172 > /sys/class/gpio/export
-# set the direction to output
-echo "out" > /sys/class/gpio/gpio172/direction
-while true;
-do
-echo 0 > /sys/class/gpio/gpio172/value #led on
-sleep 1
-echo 1 > /sys/class/gpio/gpio172/value #led off
-sleep 1
-done
-</syntaxhighlight>

Difference between revisions of "Rock/LED"

Revision as of 03:08, 18 September 2014

Contents

LEDs as class devices