Embedded Linux Multitouch with Qt, TUIO, and TSLIB

Embedded Linux Multitouch with Qt, TUIO, and TSLIB

This tutorial describes how to set up multi-touch and single-touch touchscreen input
for Qt for embedded Linux. I assume that you received a driver from your touchscreen
manufacturer or there is an existing one you can use in the Kernel source.

First things first, locate your driver ( usually /drivers/input/touchscreen/* ), and
ensure that you have every event type being defined that is required by tslib. So,
specifically you need EV_SYN, EV_ABS, and EV_KEY. My driver did not define EV_KEY,
and even though it does not report that event type, I still had to define it in the
driver source for tslib to work with the input from the driver.

set_bit(EV_SYN, aura.input_dev->evbit);
set_bit(EV_ABS, aura.input_dev->evbit);
set_bit(EV_KEY, aura.input_dev->evbit); # I had to add this line so that tslib was happy

Now build the Kernel with your driver ( either as module or driver ) and fire up your

My input device is called 'touchscreen'. Yours will probably be event1 or event0 depending
on serveral possible reasons.

See what the device is with:

# ls -rlt /dev/input/touchscreen
lrwxrwxrwx 1 root root 6 Jan 17 21:06 /dev/input/touchscreen -> event1
# chmod 777 /dev/input/touchscreen
# chmod 777 /dev/input/event1

You can see more information with:

# cat /sys/devices/virtual/input/input1/uevent
ABS=650000 0

To ensure that your driver is working do the following command and
then move your finger around the screen. You should see output here
when you finger is touching the screen.

# cat /dev/input/touchscreen | hexdump
0000000 9011 3883 565f 0001 0003 0030 0001 0000
0000010 9011 3883 565f 0001 0003 0032 0001 0000
0000020 9011 3883 565f 0001 0003 0035 04c9 0000
0000030 9011 3883 565f 0001 0003 0036 0c3f 0000
0000040 9011 3883 565f 0001 0000 0002 0000 0000
0000050 9011 3883 565f 0001 0000 0000 0000 0000
0000060 9011 3883 90a9 0001 0003 0030 0001 0000
0000070 9011 3883 90a9 0001 0003 0032 0001 0000

Go back to your host machine and download the tslib src from here
--> https://github.com/kergoth/tslib.

Enter the tslib source directory ( cd tslib/plugins ) and edit the input-raw.c file.
Replace any occurences of ABS_X / Y with ABS_MT_POSITION_X / Y. These are the names
of the multi-touch event type variables produces by a multitouch driver.

Now that everything is in order, build tslib and deploy using the following commands
to your exported nfs ( root file system ) for the board:

sudo ./autogen-clean.sh
sudo ./autogen.sh
sudo export ac_cv_func_malloc_0_nonnull=yes
sudo export PATH=`pwd`:$PATH
sudo ./configure CC=/home/user/toolchain/linaro/bin/arm-linux-gnueabi-gcc
sudo make
sudo make install
sudo cp /usr/local/tslib/bin/* /home/user/exported-nfs/usr/bin/
sudo cp /usr/local/tslib/etc/ts.conf /home/user/exported-nfs/etc/
sudo cp -r /usr/local/tslib/lib/ts /home/user/exported-nfs/usr/lib
sudo cp /usr/local/tslib/lib/* /home/user/exported-nfs/lib/
sudo vim /home/user/exported-nfs/etc/ts.conf

When ts.conf opens for editing, uncomment the 'input raw' line ( the very first
commented out module ).

Now log back into your embedded machine and export the following environment

export TSLIB_TSDEVICE=/dev/input/touchscreen
export TSLIB_CALIBFILE=/etc/pointercal
export TSLIB_CONFFILE=/etc/ts.conf
export TSLIB_PLUGINDIR=/usr/lib/ts
export TSLIB_FBDEVICE=/dev/fb0
export TSTS_INFO_FILE=/sys/devices/virtual/input/input1/uevent
export QWS_MOUSE_PROTO=tslib:/dev/input/touchscreen
export PATH=$PATH:/usr/bin

Now we are ready to calibrate. Go to /usr/bin and launch the calibration
utility. You should now see a calibration image on the screen requesting
you to touch a few crosshairs. Go ahead and do that until it stops. Then
your screen is calibrated! The calibration parameters are stored in the
/etc/pointercal file. (you may have to first increase the brightness
of your screen with --> echo 127 > /sys/class/backlight/generic-bl/brightness)

# ts_calibrate
xres = 640, yres = 480
Took 5 samples...
Top left : X = 3817 Y = 3912
Took 6 samples...
Top right : X = 269 Y = 3822
Took 5 samples...
Bot right : X = 356 Y = 550
Took 5 samples...
Bot left : X = 3732 Y = 614
Took 6 samples...
Center : X = 2202 Y = 2216
643.068298 -0.155621 -0.000056
491.792572 0.002567 -0.115674
Calibration constants: 42144124 -10198 -3 32230118 168 -7580 65536

You can also test the touchscreen mouse input by running:


Great! Now you have single mouse input with tslib ready to go!

Now let's move on to multi-touch.

Download the following packages to enable multitouch events with Qt.


Export your cross-compiler and toolchain:

export CC=/home/user/toolchain/linaro/bin/arm-linux-gnueabi-gcc
export CXX=/home/user/toolchain/linaro/bin/arm-linux-gnueabi-g++

Enter the liblo source code directory and build and deploy with:

cd /home/user/Desktop/QTUIO/liblo-0.26
./configure --prefix=/usr/local/lib/liblo --host=arm
make clean
sudo make install
cd /usr/local/lib/liblo
sudo cp bin/* /home/user/exported-nfs/usr/bin/
sudo cp lib/liblo.a /home/user/exported-nfs/usr/bin/
sudo cp lib/liblo.la /home/user/exported-nfs/usr/bin/

Enter the mtdev source code directory and build and deploy with:

cd /home/user/Desktop/QTUIO/mtdev-1.1.2
./configure --prefix=/usr/local/lib/mtdev --host=arm
make clean
sudo make install
cd /usr/local/lib/mtdev
sudo cp bin/* /home/user/exported-nfs/usr/bin/
sudo cp lib/libmtdev.a /home/user/exported-nfs/usr/bin/
sudo cp lib/libmtdev.la /home/user/exported-nfs/usr/bin/

Enter the mtdev2tuio bridge source code directory and build and deploy with:

cd /home/user/Desktop/QTUIO/mtdev2tuio
make clean
sudo cp mtdev2tuio /home/user/exported-nfs/usr/bin/

Enter the qTUIO source directory and build and deploy with:

cd /home/user/Desktop/QTUIO/qTUIO
sudo rm -rf /home/user/Desktop/QTUIO/qTUIO/lib/*
cd src/
make clean
cd ../lib
mv libqTUIO_d.so.1.0.0 libqTUIO.so.1.0.0
sudo rm -rf *libqT*_d*so*
sudo ln -sf libqTUIO.so.1.0.0 libqTUIO.so.1.0
sudo ln -sf libqTUIO.so.1.0.0 libqTUIO.so.1
sudo ln -sf libqTUIO.so.1.0.0 libqTUIO.so
sudo mkdir -p /usr/local/lib/qTUIO
sudo cp -r ../lib/* /usr/local/lib/qTUIO
sudo cp -r /usr/local/lib/qTUIO/* /home/user/exported-nfs/usr/lib/

Now kick off the server that will take multi-touch events input from
mtdev and feed that as TUIO packets to Qt:

# ./mtdev2tuio /dev/input/touchscreen osc.udp://
Sending OSC/TUIO packets to osc.udp://

Also, ensure that you exported your Qt mouse pointer input environment
variable as follows:

export QWS_MOUSE_PROTO=tslib:/dev/input/touchscreen

Now use Qt Creator or some other IDE to build and deploy the pinchzoom
example found in the qTUIO examples directory to the board.

On the board ( or from Qt Creator ) run the application like:

cd /home/test ; export QWS_MOUSE_PROTO=Tslib:/dev/input/touchscreen ; ./pinchzoom -qws

Output should look like:

Connecting to device...
Killing remote process(es)...
Starting remote process ...
Remote process started.
graphicsview initialized
listening to TUIO messages on UDP port 3333

The application will launch on your screen and you should be able to use your finger
as a mouse but also pinch and zoom ( gestures ) at the same time!

Happy coding :)

Feel free to leave feedback - happy coding

APClassy 2013