View source for How to rotate X41t screen with gravity sensor(hdaps)

[[:Category:X41 Tablet|X41 Tablet]][[Category:X41 Tablet]][[Category:Scripts]]

The X41t has a acceleration sensor build in. Originally it can protect the hard drive, if Laptop is falling down. See the [[HDAPS]] Page.
Now lets use that for funny stuff like emulate a joystick for Neverball [http://de.wikipedia.org/wiki/Neverball]. Or we use it for a very useful thing: Rotating the screen by recognizing where is downward. Like a lot of handy tools, like mobiles, mp3 player or photo cameras.

 Basic concept is the following: 
 -Rotate the screen and the stylus to the steepest decent direction.
 -Rotate only in stylus mode.
 -Rotate only if it is really necessary.
 -Rotate only if it cants more than 10 degrees.
 -An easy program.

There are other programs witch can do that, but I have not found one that works out off the box. And I can not understand that much ''python''. So I tried it out myself.
I have written a set of small ''shell'' scripts that rotates the screen of the X41 Tablet by using the gravity sensor coordinates and some ACPI events.
It consist of two parts, fist the main part that contains the code for deciding and rotating and the second part which starts and stops the fist one. Maybe some one can make suggestions to get this in a real deamon style. 

I have tested it on an x41t with ubuntu 8.04 with the standard kernel 2.6.24-19-generic.
 ''sudo apt-get install x11-xserver-utils wacom-tools'' should install all stuff.

First Part. Usually this is saved as {{path|/etc/acpi/x41t_gravity}}
 
 #!/bin/bash 
  
 #usage: just start or kill it
 
 #load configuration
 . /etc/gravity/gravity.conf
 
 get_orientation(){
     string=`cat /sys/devices/platform/hdaps/position`
     string=`echo $string | tr -d '[=-=][:blank:][=(=][=)=]'`
     x=`echo $string | awk -v FS="," '{print $1}'`
     y=`echo $string | awk -v FS="," '{print $2}'`
     dx=`expr $x - $x_horizontal`		#dx away from middle
     dy=`expr $y - $y_horizontal`		#dy away form the middle
     
      #get actual orientation from last rotation, saved in a file :
     if [ ! -f /tmp/actual_orientation.txt ];then
     	echo 0 > /tmp/actual_orientation.txt		#0 means normal orientation
     fi
     actual_orientation=`cat /tmp/actual_orientation.txt`
 }
 
 prepare_rotate(){
             echo "Nothing to prepare. I can rotate now."
 	    #ps -A | grep compiz.real && (kwin --replace)&	#because compiz sometimes crashes. 
  }
 
 do_rotate(){
 	    prepare_rotate
 	    #rotate screen
 	    xrandr -o $1
 	    #rotate stylus
  	    case $1 in
     		right)
     		    /usr/bin/xsetwacom set stylus rotate 1;;
 		left)
 		    /usr/bin/xsetwacom set stylus rotate 2;;
 		inverted)	
 		    /usr/bin/xsetwacom set stylus rotate 3;;
     		*)
 		    /usr/bin/xsetwacom set stylus rotate 0;;
 	    esac
 	    #save the orientation			
 	    echo $1 > /tmp/actual_orientation.txt
 }
 
 ######### Main ########################
 
 while [ true ]; do
     get_orientation    
      if [ `expr $dx \* $dx` -ge `expr $dy \* $dy` ];then #checks for the absolute greater value 
  	if [ $dx -gt $eps ] && [ ! $actual_orientation = right ] ;then #check if the screen have to rotate
 	    do_rotate right
 	elif [ $dx -lt -$eps ] && [ ! $actual_orientation = left ];then #check if the screen have to rotate
 	    do_rotate left
 	fi
     else
 	if [ $dy -gt $eps ] && [ ! $actual_orientation = normal ];then #check if the screen have to rotate
 	    do_rotate normal
 	elif [ $dy -lt -$eps ] && [ ! $actual_orientation = inverted ];then #check if the screen have to rotate
 	    do_rotate inverted
 	fi
     fi
     sleep 1
 done
 
 exit 0


Second Part. Usually this is saved as {{path|/etc/acpi/x41t_control_gravity.sh}}

 #!/bin/bash 
 
 #load configuration
 . /etc/gravity/gravity.conf
 
 ################ set DISPLAY ####################
 #export DISPLAY=$Default_DISPLAY		#a work around for right DISPLAY varialbe (I do not like it).
 #export XAUTHORITY=$Default_XAUTHORITY         #THIS GIVED ME AN ERROR SO I COMMENTED IT: wbonx
 #xset -display $DISPLAY dpms

 ################# Main ##########################
 
 if [ ! $1 ] || [ ! $1 = start ];then
     killall x41t_gravity		#return to normal state
     xrandr -o normal 
     /usr/bin/xsetwacom set stylus rotate 0
     rm /tmp/actual_orientation.txt
 elif [ $1 = start ];then
     #check for the kernel modul for gyroscope
     lsmod | grep hdaps || modprobe hdaps
     lsmod | grep hdaps || exit 1
     (/etc/acpi/x41t_gravity)&		#will be endless repeated (kill see up)
 fi
 
 exit 0

Some settings that have to tune. Usually this is saved as {{path|/etc/gravity/gravity.conf}}

 x_horizontal=433	#horizontal position, get it by calibration
 y_horizontal=390	#just read the value in /sys/devices/platform/hdaps/position
 			#the first value is x, second one is y
 
 eps=40			#define a neighbourhood interpreted as horizontal
 
 Default_DISPLAY=":0.0"
 Default_XAUTHORITY=/home/smjb0803/.Xauthority


Now lets begin! Just add two ACPI events, first to start the ''x41t_gravity'', second for ending it. 

Fist. Usually this is saved as {{path|/etc/acpi/events/x41t-swivel-down}}.
 # /etc/acpi/events/x41t-swivel-down
 # called when tablet head swivels down
 event=ibm/hotkey HKEY 00000080 00005009
 action=/etc/acpi/x41t_control_gravity.sh start

Second. Usually this is saved as {{path|/etc/acpi/events/x41t-swivel-up}}.
 # /etc/acpi/events/x41t-swivel-up
 # called when tablet head swivels up
 event=ibm/hotkey HKEY 00000080 0000500a
 action=/etc/acpi/x41t_control_gravity.sh stop

And restart the ACPID.
  sudo /etc/init.d/acpid restart

That`s it. Have fun and make suggestions. Please use it only if you trust in it. On personal risk. You have to prevent losing data. 
--[[User:Jonasbergel|Jonasbergel]] 09:27, 16 October 2008 (CEST)