On Sun, Jul 02, 2017 at 12:00:39PM +0200, Jörg Zywek wrote: > Hi, > I'm using Raspberry Pi 2B, actual Raspian Jessie (Jun 2017) and a eGalax 8" > touchscreen. In general I've got the touchscreen working by modifying the > TransmissionMatrix to the following values: > > Option "TransformationMatrix" "0 1 -0.001 -1 0 0.995 0 0 1" > (The display is rotated to 180 degrees by rotate instruction in the > /boot/config.txt file.) > > The position of the shown cursor is quite exactly, if I point at the middle > of the screen. But when I move to right or to left the cursor won't follow > the pen exactly: the more I reach the right (or left) margin of the display > the cursor follows less. When I touch the right border of the display, the > cursor stands about 30 pixels left from the physical position of the pen. At > the left side it's just the opposite behaviour. Moving up an down, the > cursor "loses" about 50 pixels from the physical position at the top or > bottom of the display. > > The strange values above (-0.0001 or 0.995) are incremental tries to > approach the correct behaviour. But I'm not sure, that it is the right und > promising path.
yes, that's the right path. You need to find a matrix that provides the correct mapping, don't worry about screen-edge clipping because the server will handle that anyway. Unless the device has non-linear calibration, there will be a matrix that will make the device pixel-precise or almost so. > And I can't find any reference manual what the values of the > TransformationMatrix are standing for. Can you help me or give me a hint. The first two links that come up for me are: https://wiki.ubuntu.com/X/InputCoordinateTransformation https://wiki.archlinux.org/index.php/Calibrating_Touchscreen but it's just a standard coordinate transformation matrix so you can work the various angles and offsets in as well. Wikipedia has heaps of information about those (maybe too much :) Cheers, Peter _______________________________________________ xorg@lists.x.org: X.Org support Archives: http://lists.freedesktop.org/archives/xorg Info: https://lists.x.org/mailman/listinfo/xorg Your subscription address: %(user_address)s