Re: AM335x touchscreen issues

Michael Welling
2015-05-26T21:50:49Z

On Tue, May 26, 2015 at 09:36:57PM +0000, Griffis, Brad wrote:
>
> > -----Original Message-----
> > From: Cooper Jr., Franklin
> > > -----Original Message-----
> > > From: Michael Welling [mailto:mwelling79@gmail.com] On Behalf Of
> > > Michael Welling
> > > Sent: Tuesday, May 26, 2015 4:29 PM
> > > To: Cooper Jr., Franklin
> > > Cc: Balbi, Felipe; dmitry.torokhov@gmail.com; R, Vignesh; Griffis,
> > > Brad; jic23@kernel.org; wsa@the-dreams.de;
> > > linux-input@vger.kernel.org; GWilson@sakuraus.com;
> > > linux-iio@vger.kernel.org
> > > Subject: Re: AM335x touchscreen issues
> > >
> > > On Tue, May 26, 2015 at 09:15:53PM +0000, Cooper Jr., Franklin wrote:
> > > > Michael,
> > > >
> > > > Can you send me the output of ts_test_raw after you done a 5 or so
> > > > touch
> > > down and touch up events? In the output let me know at which point in
> > > the log that the issue you observed has occurred. Please try to avoid
> > > moving your finger since I want to see the full output of that program
> > > but I'm not interested any unnecessary pen down events.
> > > >
> > >
> > > Oddly the repeated pen up and down events do not occur when running
> > > ts_print_raw:
> > > root@som3517-som200:~# ts_print_raw
> > > 1418169393.147827: 1648 2075 206
> > > 1418169393.229976: 1725 1983 240
> > > 1418169393.312154: 1731 1980 240
> > > 1418169393.394333: 1706 2043 239
> > > 1418169393.476523: 1703 2028 241
> > > 1418169393.558708: 1714 2041 240
> > > 1418169393.640888: 1704 2041 240
> > > 1418169393.721556: 0 0 0
> > > 1418169395.283096: 2889 2512 192
> > > 1418169395.365236: 2947 2486 210
> > > 1418169395.447413: 2949 2470 211
> > > 1418169395.529606: 2943 2497 211
> > > 1418169395.611759: 2922 2506 211
> > > 1418169395.693935: 2866 2474 213
> > > 1418169395.776135: 2858 2481 214
> > > 1418169395.858305: 2861 2451 213
> > > 1418169395.938972: 0 0 0
> > > 1418169397.482867: 1083 1981 236
> > > 1418169397.565026: 1157 1832 254
> > > 1418169397.647217: 1161 1856 256
> > > 1418169397.729412: 1158 1883 255
> > > 1418169397.811583: 1159 1841 255
> > > 1418169397.893760: 1159 1864 256
> > > 1418169397.975947: 1158 1893 256
> > > 1418169398.056605: 0 0 0
> > > 1418169399.690290: 2299 2372 178
> > > 1418169399.772432: 2388 2160 221
> > > 1418169399.854611: 2391 2190 223
> > > 1418169399.936802: 2379 2207 223
> > > 1418169400.018966: 2389 2184 223
> > > 1418169400.101146: 2383 2208 224
> > > 1418169400.183338: 2381 2203 223
> > > 1418169400.264012: 0 0 0
> > > 1418169402.073266: 1230 2381 212
> > > 1418169402.155413: 1301 2097 247
> > > 1418169402.237590: 1313 2077 248
> > > 1418169402.319772: 1307 2126 248
> > > 1418169402.401948: 1304 2096 248
> > > 1418169402.484127: 4078 2155 58
> > > 1418169402.564801: 0 0 0
> > >
> > > Here is what the output of ts_test looks like without even touching
> > > the
> > > screen:
> > > root@som3517-som200:~# ts_test
> > > 1418169549.722957: 816 17 58
> > > 1418169549.803604: 816 17 0
> > > 1418169549.817757: 816 25 58
> > > 1418169549.898411: 816 25 0
> > > 1418169549.912828: 816 41 59
> > > 1418169549.993463: 816 41 0
> > > 1418169550.007771: 816 28 58
> > > 1418169550.088404: 816 28 0
> > > 1418169550.102828: 816 33 58
> > > 1418169550.183486: 816 33 0
> > > 1418169550.197767: 816 42 59
> > > 1418169550.278401: 816 42 0
> > > 1418169550.292970: 816 23 58
> > > 1418169550.373604: 816 23 0
> > > 1418169550.387773: 816 28 58
> > > 1418169550.468404: 816 28 0
> > > 1418169550.482955: 816 32 59
> > > 1418169550.563600: 816 32 0
> > > 1418169550.577773: 816 25 58
> > > 1418169550.658406: 816 25 0
> > > 1418169550.672827: 816 35 59
> > > 1418169550.753464: 816 35 0
> > > 1418169550.767761: 816 42 59
> > > 1418169550.848407: 816 42 0
> > > 1418169550.862826: 816 41 59
> > > 1418169550.943462: 816 41 0
> > > 1418169550.958013: 816 37 59
> > > 1418169551.038655: 816 37 0
> > > 1418169551.052824: 816 41 59
> > > 1418169551.133475: 816 41 0
> > > 1418169551.147774: 816 28 58
> > > 1418169551.228406: 816 28 0
> > [Franklin] So your saying the above ts_test is being ran and you never
> > touched the screen? Looking at the mailing list post you sent earlier it seems
> > like the goal is for the ADC to be used at the same time. Is that the case when
> > you ran both ts_test and ts_print_raw?
>
> I was also wondering if this relates to raw ADC samples being captured. The TSCADC should not be capturing anything at all if the screen is not touched. You need the pen-down event to initiate the capture sequence. I'm curious what the state of the pins is during this occurrence, i.e. are we actually seeing some kind of event on the lines? I suspect that something is misconfigured somewhere, perhaps resulting in a change of state in the pins that registers as a pen-down.

Then why would reverting a commit make the problem go away?

It seems to have something to do with the characteristic of the touchscreen
as this does not happen on my 7" display.

Looking at the datasheet these pin are dedicated analogs and cannot be
MUX'd otherwise.

http://www.ti.com/lit/ds/symlink/am3354.pdf
page 20