ep12 / pytouchd

Python driver for some touch screens like the ODROID VU7+ etc.

pytouchd

Python driver for some touch screens like the ODROID VU7+ etc.

History

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:

1. 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.)
2. 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!

Tests

touch device	SBC	status
ODROID VU7+	RasPi3	beta, dblClick not good

Installation

1. Always load the UInput module:

   sudo echo uinput >> /etc/modules

2. 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

3. Clone this repo
4. Install start-up script TODO

Options

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