Python driver for some touch screens like the ODROID VU7+ etc.
After googling around it seems to be harder than it should to get the touch functionality of some touch displays working. In the initial case, the ODROID VU7+ screen with the Raspberry Pi 3 SBC works perfectly fine as a display but without input. Compiling a new kernel that can handle the different type of input was too much work for such a small thing. In a post concerning that problem (VU7+ and RPI3) it was stated that the current support for other monitors should be kept and my idea was that it is possible to write a driver that is capable of handling both types of input since only two tiny details have chainged:
- In the original struct, every coordinate is one byte. So a point (x, y) is two bytes in length. If you have a display with a 4K resolution (3840 x 2160), many different input presses on different pixels will appear with the same two bytes. In that example, a touch in a 15x8 pixels area is quite a big of an error. My VU7+ sends two bytes instead of one for each coordinate. That means, the touch resolution is way better! (65536 instead of 256 display parts for each axis.)
- The mode is not limited to be relative (0 = 0%, 255 = 100%), the exact absolute pixel coordinate is sent!
This driver is a (proof of) concept for a universal driver as described above. If the driver detects that a point (2 coordinates) consists of 2 bytes (bpc (bytes per coordinate) is 1), the mode is set to relative, for bpc==2 the absolute mode is chosen.
If you want to, you can adapt this idea, especially if you are working on the kernel that should be handling touch input!
| touch device | SBC | status |
|---|---|---|
| ODROID VU7+ | RasPi3 | beta, dblClick not good |
- Always load the UInput module:
sudo echo uinput >> /etc/modules
- Install python3 and dependencies:
sudo apt-get install python3 python3-pip # try with sudo if it doesn't work (I have strange errors, but it works perfectly as root ?_?) pip3 install -U numpy evdev - Clone this repo
- Install start-up script TODO
| name | type | default value | comment |
|---|---|---|---|
| live | bool | false | disable all enhancements and foward the raw input |
| dblClickTime | float | if a click is registered within x seconds after the last click has begun and the new position is within the dragDist radius, the DBL mode is set. | |
| holdForRightClick | bool | true | perform a right click when pressing the touch screen for longClickTime seconds |
| longClickTime | float | in seconds | |
| dragDist | custom | defines the distance that must be exceeded to start a drag. In px, in, cm, mm if devW and devH are given, else: pixels | |
| devW, devH | custom | the phyical measurements of the touch area in cm, mm, in |