Am 22.09.2016 um 12:35 schrieb Michael Mrozek EvilDragon@openpandora.org:
Am Wed, 21 Sep 2016 19:41:09 +0200 hat "H. Nikolaus Schaller" hns@goldelico.com geschrieben:
Hi,
- These touchscreens are ACCURATE without any jitter. All other
touchscreens tried before were jittering a lot - and I thought this was something to fix in the driver.
Well, the driver can only filter jitter and try to suppress it, but it reduces precision.
Oh, than this one seems to be a LOT better than all the other ones I tried. Great!
- However: They still need more force to react than on the Pandora.
Which reminded me: The Pandora touchscreen is pressure sensitive (255 values, if I remember correctly?) So this one should ALSO be pressure sensitive. Could it be that you can change the sensitivity in the driver?
The driver also reports pressure values - but only if you you press more than some minimum pressure. This is to support debouncing.
Good to know :)
That would explain why the touchscreen needs more force to react - even though it's the exact same as on the Pandora. Could someone check the driver to see whether there's some setting or whether it could be added?
Yes, there is a minimum pressure value. And the resistance of the touch should correctly been set or the pressure isn't calculated properly: http://git.goldelico.com/?p=gta04-kernel.git;a=blob;f=arch/arm/boot/dts/pyra...
This means:
- touchscreen-max-pressure
- ti,max-rt
- ti,x-plate-ohms
must be matched with the touch.
Ah, but that's hardcoded in the driver, so you can't change the parameters without recompiling it, I guess.
Yes, because the assumption is that plate resistance and max-pressure are constants and describe hardware.
Maybe we can do that when I visit you to work on the power supply weirdnesses (if we find the time).
Yes, we can try. Should not be too difficult.
BR, Nikolaus