Matrix Browser and Touchscreen Size

matt minga

I am using the TI AM335X-EVMSK with TI processors SDK 2.00.01. I have built an image using default configurations. I was able to launch the matrix browser and confirm that touch was working adequately.

I then disconnected the screen and attached an 800x480 panel. This panel is also resistive. I modified the panel timings to support this screen. I booted the EVM and the screen turned on appropriately the tslib calibration tool screen came up and I was able to calibrate the screen. The matrix browser launched and the touch pointed were off from the calibration. I launched the ts_test tool and saw that my calibration till appeared correct. I also launched the fingerpaint example included in the qt library and saw that it was off as well.

I assumed that redoing the calibration was allow the qt application to track properly is this not the case? Do you have any suggestions on how to resolve this issue?

Regards,

Matt Minga

over 10 years ago

0 Biser Gatchev-XID over 10 years ago

TI__Guru**** 393215 points

Check this wiki to see if you have done everything correctly: processors.wiki.ti.com/.../How_to_Recalibrate_the_Touchscreen

0 matt minga over 10 years ago in reply to Biser Gatchev-XID

Intellectual 715 points

Biser,

Thank you for the link. This happened to be the first place that I started.

Regards,

Matt Minga

0 matt minga over 10 years ago in reply to matt minga

Intellectual 715 points

Biser,

It does not resolve the issue.

Regards,
Matt Minga

0 Biser Gatchev-XID over 10 years ago in reply to matt minga

TI__Guru**** 393215 points

I have asked the software team for suggestions.

0 Kemal R. Shakir over 10 years ago in reply to Biser Gatchev-XID

TI__Guru 55345 points

Hello Matt,

Could you attached the 800x480 panel, then remove the /run/media/mmcblk0p1/pointercal and /etc/pointercal before doing a calibration.

Best regards,
Kemal

0 matt minga over 10 years ago in reply to Kemal R. Shakir

Intellectual 715 points

This was already done. This issue persists.

The calibration does not seem to hold. I can reboot the system and the ts_test application will no longer track. Sometimes I can calibrate the screen, sometimes I am only able to touch one or two points before the calibration wraps up, and sometimes the calibrations finishes as soon as I launch it.

I have looked at several other examples for touch screens, including the full sized evm with 7 inch touch screens. The device tree for that device does not make any adjustments that are not accounted for by the evmks.

Regards,
Matt Minga

0 Brad Griffis over 10 years ago in reply to matt minga

TI__Guru*** 125430 points

matt minga said:
Sometimes I can calibrate the screen, sometimes I am only able to touch one or two points before the calibration wraps up, and sometimes the calibrations finishes as soon as I launch it.

Try setting charge delay to a larger value in the dts, e.g. 0x1000, 0x4000, 0x8000, 0xC000, etc.

ti,charge-delay = <0x4000>;

You might also check your grounding, e.g. is the touchscreen secured tightly, ribbon cables have good connections, etc.

0 matt minga over 10 years ago in reply to Brad Griffis

Intellectual 715 points

I was able to break the pins out on the original touch screen from the the EVM and run them through my prototype harness without an issue. I ran the 7 inch screen on another controller, a TSHARC, from Hampshire without issue.

Back on the EVM, I am using different charge delay values hoping to come up with something. I am still having issues with the calibration tool jumping through the test points. The first point tends to be the best. After that it seems upper right or lower right will wind up skipping the rest once the touch is made.

0 matt minga over 10 years ago in reply to matt minga

Intellectual 715 points

I did make a go at some decoupling capacitors but did not have good results. I imagine doing so would require a bit more investigation than I had time for. I went with decoupling caps on AIN0-AIN3 of .1 uF. I was unable to find delays that allowed enough time for settling. I was not able to pass calibration with the caps in place.

I have noticed that none of the reference screens make provisions for the any decoupling capacitors. I have also noticed that none of the device tree files make use of anything other than the charge delay.

I did see in the errata that there are some notes on touch screen.

Thank you for your help.

Regards,
Matt Minga

0 matt minga over 10 years ago in reply to matt minga

Intellectual 715 points

It turned out to be noise. We were using a series of interposer boards and bench wiring to adapt the screen to the EVM. Once we laid out a board to reduce this mess, the issue went away.

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Matrix Browser and Touchscreen Size