Posted on December 22, 2016 at 18:19Imen, Thank you for the reply. I have since also purchased the STM32F769 Discovery which has the same display and touchscreen. Unfortunately, though this board is better, it has the same non-linearity problem. For instance, drawing across the board and placing a pixel at the touched locations, the resulting line is not straight. I would be able to work with it being higher or lower on the board as long as the line was straight. The line curves and the only way to resolve this would be to plot each point into an array with the resulting actual location. I've looked at one of the paint programs, I believe the one you reference, and it uses a calibration routine that only handles the up/down and left/right issues. It can't possibly handle a wavy line calibration issue.
Other boards that use the smaller, lower resolution screens including the STM32F746 do not have this problem. So the touch screen on these boards are basically unusable for any amount of detailed resolution. If your application keeps the touch sensitive areas from stacking on top of each other, then it will work since the linearity issue is related to the vertical resolution (e.g. if you draw a straight line vertically when the display is in landscape mode then the line is straight).
Again, thank you for the reply.
