It is the LG screens.  There is a bad board design and there seems to be around +-1V high frequency noise at the touch device controller on the chestnut boards according to my o-scope.  I've given up for now, and am now banging my head on other gumstix things...


On Tue, Mar 6, 2012 at 5:04 AM, Mark Zieg <mark.zieg@oceanoptics.com> wrote:
Hi Christian,

Are the screens LG or Samsung?  We experienced exactly what you describe with LG, but the Samsung ones worked much better.

Try adding the InvertY option to your /usr/lib/X11/xorg.conf.d/05-evdev.conf:

Section "InputClass"
       Identifier "evdev touchscreen catchall"
       MatchIsTouchscreen "on"
       MatchDevicePath "/dev/input/event*"
       Driver "evdev"
       Option "InvertY" "true"
EndSection

Calibrate your screen using a script like this (get ts_calibrate from 'apt-get install tslib')

$ cat scripts/calibrateScreen.sh
#!/bin/bash
EVENT=`ls /dev/input/ | grep event`
sudo TSLIB_TSDEVICE=/dev/input/$EVENT /usr/bin/ts_calibrate

(I assume you've already done the "setenv defaultdisplay lcd43" bit.)

Also, occasionally we find that the screens don't want to act as input devices following a boot, so we bounce the driver using a script like this:

$ cat scripts/bounceTouch.sh
#!/bin/bash
sudo modprobe -r ads7846
sleep 1
sudo modprobe ads7846

We've been reasonably happy with the screens after following these steps.  Not thrilled, but they get the job done.

-MZ

-----Original Message-----
From: Christian Ruocco [mailto:xris.ruocco@gmail.com]
Sent: Tuesday, March 06, 2012 3:01 AM
To: gumstix-users@lists.sourceforge.net
Subject: Re: [Gumstix-users] LCD touch screen unusable on Overo/Chestnut

I have this issue with all 10 of our Overo/Chestnut combos.. Erratic touchscreen behavior and it also seems you have to press really hard on the screen to get consistent samples, and then they're still not very consistent. When I say really hard I mean substantially more than the light brush needed to use an iPhone or the Verdex/ConsoleLCD16-vx for an example.
I have even put some debugging code in the driver to determine how reliably the PENIRQ fires, and it is inconsistent, so I'm assuming this is a hardware issue? There have been suggestions that it's somehow tied to the LCD refresh rate.  I have experimented with that and found that there is no correlation for me at least.  I have also used the prebuilt images on Gumstix site to double check I haven't mangled something. I used the SD image from http://cumulus.gumstix.org/images/angstrom/factory/2011-08-30-1058/ and using X-Windows on that exhibits the same problem.

Any suggestions are welcome!

Kind Regards,
Christian Ruocco

--
View this message in context: http://gumstix.8.n6.nabble.com/LCD-touch-screen-unusable-on-Overo-Chestnut-tp561488p4550477.html
Sent from the Gumstix mailing list archive at Nabble.com.

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