Car PC touchscreen

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Navit will run on any Linux-compatible hardware, from your high-end desktop to computer to gpe-compatible handhelds like the HTC BlueAngel.

We'll eventually post here some tips about specific hardware.


If you're planning to use NavIt, then probably you want to take it out with you on the roads. You can put it on your handheld, but you can also put a computer in your car, and drive it using a Touchscreen.

The VM-84 Touchscreen[edit]

This is a really cheap TouchScreen, sold from You can get it for usually 200$, when a lilliput or equivalent will cost around 300$. And, as a NavIt use, you get 5% discount on the shop!

The only drawback with this touchscreen is its driver. It was a real pain to get it to work the first time. The device is shipped with some drivers, which are nothing but relevant. But now, thanks to this page, it's easy :)

Note : All the credit for this work goes to Martin "cp15" S., who hacked the elographics driver and made it work.

The USB to Uart bridge.[edit]

This screen use in fact the cp2101 driver module, for the USB to Uart bridge. So, the first step is to ensure the cp2101 module is loaded. It's shipped with the kernel :

Symbol: USB_SERIAL_CP2101 [=m]

-> Device Drivers
-> USB support
-> USB Serial Converter support
-> USB Serial Converter support (USB_SERIAL [=m])

Once the module is loaded, and the device is plugged, you should get a /dev/ttyUSB0 device. It could be a good time to test it before continuing.

od -h -w10 </dev/ttyUSB0

Touch the screen. You should get datas, something like this :

0000000 55 54 02 ec 0c 90 06 90 00 73 55 54 04 ec 0c 90
0000020 06 90 00 75 55 54 02 60 0b 00 07 00 00 c7 55 54
0000040 04 60 0b 00 07 00 00 c9 55 54 02 54 0a 98 07 98
0000060 00 ea 55 54 04 54 0a 98 07 98 00 ec 55 54 02 c8

Warning: if you have no input on the VGA, or if your input is set to something other than VGA (like RCA1) then the touchscreen functionnality will be disabled by the screen. This mean that it won't send datas to your computer. It took me a while to realize this, and i was thinking that i had a problem with the cp2101 driver.

The Xorg input driver[edit]

Now, you need to get the hacked xorg-input-elographics driver. The patch has been submitted to freedesktop, but it will probably take some time (and work) to have it bundled within elographics. The bug entry is here :

Until then, you can do the following :

Install xorg-server dev kit. Depending on your distro, it can be xorg-server (Gentoo), xorg-x11-server-sdk (OpenSuse), ...

Get an already patched tarball, extract and build :

tar xvfz xf86-input-elographics-1.1.0-VM84.tgz
cd xf86-input-elographics-1.1.0
./configure --prefix=/usr && make

And install as root :

make install

Now, configure your xorg.conf. Add something like this somewhere in your /etc/X11/xorg.conf :

Section "InputDevice"
  Driver       "elographics"
  Identifier   "TouchScreen"
  Option       "ButtonNumber" "1"
  Option       "ButtonThreshold" "17"
  Option       "Device" "/dev/ttyUSB0"
  Option       "InputFashion" "Touchpanel"
  Option       "MaxX" "3868"
  Option       "MaxY" "272"
  Option       "MinX" "231"
  Option       "MinY" "3858"
  Option       "Name" "ELO;2300-TOUCHSCREEN"
  Option       "ReportingMode" "Scaled"
 Option       "SendCoreEvents" "on"
# Option "DebugLevel" "9"

And add the driver to Section "ServerLayout"

 InputDevice    "TouchScreen" "SendCoreEvents"

Restart X, and voila!