Hi,
Am 21.09.2016 um 18:26 schrieb Michael Mrozek EvilDragon@openpandora.org:
Hi,
BOE was visiting me today and I also received the new touchscreens from Fatih ago (the ones using the exact same material as the Pandora touchscreens).
Well, looks like the company that delivered the touchscreens to BOE used a wrong material, as the touchscreens were grainy again (and the first sample in the wrong size wasn't), so no need to comment on these, as they were wrong.
However, I tried the ones from Fatih and FINALLY we have touchscreens which do NOT degrade the picture quality. Yay!
But there's something else that's interesting:
- 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.
But these now don't jitter at all, the pointer stays exactly on one spot when keep the stylus pressed down.
This is great!
And they ALWAYS hit exactly where I press! I can also access every corner and the top and bottom which was always an issue with the previous touchscreens.
- 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.
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.
(don't be worried by the FIXME for the interrupt - it would be a duplicate entry and should be deleted in the mainboard DTS)
I'm not sure whether that's related to the touchscreen controller as well - how does this work on the Pandora?
Basically the same. Although Pandora OS does not have these parameters.
With Letux kernel for Pandora it is here:
http://git.goldelico.com/?p=gta04-kernel.git;a=blob;f=arch/arm/boot/dts/omap...
BR, Nikolaus