===== Automatic LCD brightness control =====

EEE is able to automatically adjust the LCD brightness depending on whether you are working on AC power or battery.


==== Instructions ====

1. In the console type

  kwrite /home/user/.screen_brightness.sh

2. Put the following text in the file

<code bash>
  #!/bin/sh

  PWR_STATE=`cat /proc/acpi/ac_adapter/AC0/state | awk '{print $2}'`

  if [ "$PWR_STATE" == "off-line" ] ; then
        echo 5 > /proc/acpi/asus/brn
  else
        echo 15 > /proc/acpi/asus/brn
  fi
</code>

The 5 and 15 can be set to anything you like. 0 is dimmest and 15 is brightest.

3. Save the file, exit and make it executable with

  chmod +x /home/user/.screen_brightness.sh

4. Next, type

  sudo kwrite /etc/acpi/hotkey.sh

5. You should see something like that on the end of the file
<code bash>
  #Fn+F4
  0000002x)
          #echo "Brightness Up" > /dev/pts/0
          ;;
esac
</code>

6. Insert
<code bash>
  # Power cord in or out
  00000050 | 00000051 )
          sudo -u user /home/user/.screen_brightness.sh
          ;;
</code>

between ;; and esac, so the end of the file should look like
<code bash>
  #Fn+F4
  0000002x)
          #echo "Brightness Up" > /dev/pts/0
          ;;
  # Power cord in or out
  00000050 | 00000051 )
          sudo -u user /home/user/.screen_brightness.sh
          ;;
esac
</code>

7. Save the file, exit the editor and restart the system.

Now the brightness should change automatically when you plug/unplug the AC power, but will not change depending on the power status when you boot. To change that, first follow the instructions on [[howto:startupscript|how to make a script run at startup]].

Then call .screen_brightness.sh from your startup script. For Easy Mode, type

  kwrite /home/user/.icewm/startup

and put the following text in it

<code bash>
  #!/bin/sh

  if [ -x /home/user/.screen_brightness.sh ]; then
        /home/user/.screen_brightness.sh
  fi
</code>

then make it executable with

  chmod +x /home/user/.icewm/startup

and your Eee will automatically set its brightness at boot time


==== Relative brightness change ====

The upper script changes the brightness to a fixed value but it is also possible to do a relative change, for example: change the brightness 5 steps down when you start working on battery (and vice versa). Putting the following line in your /etc/acpi/hotkey.sh will do this.
<code bash>
  # AC power
  00000050)
          BRN=`cat /proc/acpi/asus/brn`
          if [ $(($BRN+5)) -gt 15 ]; then
              echo 15 > /proc/acpi/asus/brn
          else
              echo $(($BRN+5)) > /proc/acpi/asus/brn
          fi
          ;;
  # battery power
  00000051)
          BRN=`cat /proc/acpi/asus/brn`
          if [ $(($BRN-5)) -lt 0 ]; then
              echo 0 > /proc/acpi/asus/brn
          else
              echo $(($BRN-5)) > /proc/acpi/asus/brn
          fi
          ;;
</code>



==== Remember previous brightness ====

Most computers will automatically change your screen brightness to the brightness you had previously in a given mode.

Putting the following code in your /etc/acpi/hotkey.sh

<code bash>
	# Power cord in
	00000050)
		echo `cat /proc/acpi/asus/brn` > /home/user/.screenbright_bat
		echo `cat /home/user/.screenbright_ac` > /proc/acpi/asus/brn
		;;
	# Power cord out
        00000051 )
		echo `cat /proc/acpi/asus/brn` > /home/user/.screenbright_ac
		echo `cat /home/user/.screenbright_bat` > /proc/acpi/asus/brn
		;;
</code>

Will enable your Eee PC to do the same