PROCESSOR-SDK-AM437X: 5-wire touchscreen issue

user5926475

Expert 1270 points

Part Number: PROCESSOR-SDK-AM437X
Other Parts Discussed in Thread: AM4379

Hi,

We connect touchscreen 5 pins to AM4379 ADC0 5 input channels as following:

AIN0-XP, AIN1-XN, AIN2-YP, AIN3-YN, AIN4-WIPER

Then modified tscadc in DT file as:

&tscadc {
   status = "okay";
    tsc {
         ti,wires = <5>;
         ti,x-plate-resistance = <80000>;
         ti,coordinate-readouts = <5>;
         ti,wire-config = <0x00 0x11 0x22 0x33>;
         ti,charge-delay = <0xf000000>;
   };
   adc {
         ti,adc-channels = <5 6 7>;
   };

};
When click the screen, the cursor position can move following the click with ts_test. but it can sometimes give a false cursor position except the click position(one click, give two positions, as if quickly click two times).

If click the screen quickly , it give the false position more often. It appear about 1 false position every 40 times click under normal click operation with above tscadc setting.

We change the x-plate-resistance from 300 to 100000 and chrge-delay from 800 to f00000, but we can not get a desired result.

We test the touchscren with USB driver, it is stable..

Our SDK is sdk-05.01.00.11. linux version is 4.14.67,

Best Regards,

Dudechao

over 5 years ago

0 Nick Saulnier over 5 years ago

TI__Guru** 102640 points

Hello Dudechao,

Could you clarify what you mean by "false position"? Do you see this issue when using a stylus, or only when using a finger?

Regards,

Nick

0 user5926475 over 5 years ago in reply to Nick Saulnier

Expert 1270 points

Hello Nick,

"false position" I mean when I click the screen once, the cursor moved to two or more other positions except the pointed position. the other positions I called the false position.

For example, when I click the screen in position A, the cursor appear in position B, then return to position A. the B is different with A and not clicked there. the position B I called the false position.

No matter whether I using a stylus or a finger, the phenomenon is the same.

Best Regards!

Dudechao

0 user5926475 over 5 years ago

Expert 1270 points

Hello Nick,

Can you help us debug the 5-wire touchscreen which is beyond our capacity? We can do any test as you need.

I'm look forward to your help!

Best Regards!

Dudechao

0 Nick Saulnier over 5 years ago in reply to user5926475

TI__Guru** 102640 points

Hello Dudechao,

I apologize for the delayed response. I am checking with the developers now.

"We test the touchscreen with USB driver, it is stable" - Do you mean that a USB mouse works as expected? Or do you mean something else?

Regards,

Nick

0 user5926475 over 5 years ago in reply to Nick Saulnier

Expert 1270 points

Hello Nick,

Thank you for your response!

"We Test the touchscreen with USB driver, it is stable", I only verifiy that the touchscreen is correct with USB. and judge the problem is in the tscadc mouse driver, not the touchscreen self.

USB mouse works as expected.

Best Regards,

Dudechao

0 user5926475 over 5 years ago in reply to user5926475

Expert 1270 points

Hello Nick,

We are still waitting for your support.

We are using USB mouse without the 5-wire touch driver now, but it need a hardware driver and occupy a extra space which is not suitable for our product.

We can do any test as you need for the 5-wire touch driver.

Thank you.

Best Regard,

Dudechao.

0 Nick Saulnier over 5 years ago in reply to user5926475

TI__Guru** 102640 points

Hello Dudechao,

From a hardware standpoint:
Are the digital lines of the LCD on a separate strip from the analog lines of the touchscreen? (the digital and analog lines should not be close to each other)
Is the touchscreen firmly mounted?

Could you attach logs of touch coordinates using ts_test? Printing ts_test log to the console adds to the system load, so it is better to redirect the capture to a log file.

Regards,

Nick

0 user5926475 over 5 years ago in reply to Nick Saulnier

Expert 1270 points

Hello Nick,

The touchscreen and the displayer are two separate strips to our board, the touchscreen is 5 analog lines strip to our board and is firmly mounted.

We attach 4 log files with ts_test:

1) ts_test_1point.log: click touchscreen only once, this is ok;

2)ts_test_1point_2cursor.log:click touchscreen only once, but a false cursor appear;

3)ts_test_always_press.log: press the touchscreen a position and stay there for a moment;

4)ts_test_four-corners-center.log: click the touchscreen 4 corners and its center(not exactly).

In 1) 4) cursor are correct ; In 2), the cursor appear two positions with one click; In 3), the cursor is not steady.

Best Regards,

Dudechao

Fullscreen 3750.ts_test_1point.log Download

root@am437x-evm:~# ./ts_test 
1592976978.524154:    352    403    231
1592976978.611502:    352    403      0
^Csignal 2 caught
root@am437x-evm:~#

Fullscreen 5126.ts_test_1point_2cursor.log Download

[BEGIN] 2020/6/24 13:40:34

root@am437x-evm:~# 
root@am437x-evm:~# ./ts_test 

1592977326.366923:    233    609    435
1592977326.455944:    824    656     11
1592977326.543303:    824    656      0
^Csignal 2 caught
root@am437x-evm:~# 
[END] 2020/6/24 13:42:08

Fullscreen 1212.ts_test_always_press.log Download

[BEGIN] 2020/6/24 13:38:55
./ts_test 
1592977234.563035:    800    202    101
1592977234.651973:    800    199    136
1592977234.740986:    800    198    180
1592977234.829960:    800    198    192
1592977234.918946:    800    197    147
1592977235.007942:    800    197    167
1592977235.096933:    800    198    165
1592977235.185900:    800    197    168
1592977235.274889:    800    197    170
1592977235.363894:    800    198    154
1592977235.452879:    800    198    134
1592977235.541878:    799    198    129
1592977235.630863:    800    197    175
1592977235.719850:    800    197    176
1592977235.808846:    799    197    125
1592977235.897836:    800    197    175
1592977235.986827:    800    197    127
1592977236.164802:    799    198    249
1592977236.253805:    800    198    243
1592977236.342788:    800    198    156
1592977236.431781:    800    198    165
1592977236.520775:    800    198     74
1592977236.609758:    800    198     34
1592977236.698756:    800    197     75
1592977236.787745:    800    197     88
1592977236.876728:    799    197    131
1592977236.965741:    800    197    171
1592977237.054728:    800    197    190
1592977237.143725:    800    197    158
1592977237.232710:    800    197    111
1592977237.321703:    800    197     95
1592977237.410706:    800    197     77
1592977237.499693:    800    197    158
1592977237.588686:    800    197    192
1592977237.677670:    800    197    175
1592977237.766663:    800    197    220
1592977237.855700:    799    197    234
1592977237.944691:    800    197    218
1592977238.033691:    800    197    168
1592977238.122693:    800    197    135
1592977238.211681:    800    197    247
1592977238.300670:    800    197    178
1592977238.389661:    800    197    173
1592977238.478648:    800    197    225
1592977238.567640:    800    197    175
1592977238.656634:    800    197    174
1592977238.745626:    800    197    179
1592977238.834618:    800    197    147
1592977238.923608:    800    197    247
1592977239.012599:    800    197    275
1592977239.101589:    800    197    245
1592977239.190577:    800    197    192
1592977239.279563:    800    197    107
1592977239.368544:    800    197     67
1592977239.457549:    800    197     38
1592977239.546545:    800    197     74
1592977239.635508:    800    197    160
1592977239.724497:    800    197    262
1592977239.813459:    800    197    194
1592977239.902452:    800    197    267
1592977239.991443:    800    197    352
1592977240.080434:    800    197    264
1592977240.169424:    800    197    263
1592977240.258415:    800    197    217
1592977240.345775:    800    198      0
^Csignal 2 caught
root@am437x-evm:~# 
[END] 2020/6/24 13:40:27

Fullscreen 3034.ts_test_four-corners-centor.log Download

[BEGIN] 2020/6/24 13:36:56
./ts_test 
1592977096.090765:     20     62    133
1592977096.179746:     17     62    338
1592977096.267084:     15     62      0
1592977097.160598:    991     74    355
1592977097.249585:    991     74    183
1592977097.336944:    991     74      0
1592977098.036505:   1007    745    268
1592977098.125457:   1007    746    356
1592977098.212817:   1007    746      0
1592977099.071811:      0    732    143
1592977099.160794:      0    730    138
1592977099.248162:      0    729      0
1592977099.960544:    493    346     52
1592977100.049537:    490    345    287
1592977100.136892:    488    344      0
^Csignal 2 caught
root@am437x-evm:~# 
[END] 2020/6/24 13:38:06

0 Nick Saulnier over 5 years ago in reply to user5926475

TI__Guru** 102640 points

Hello Dudechao,

I am guessing that for 2), the correct location was (233,609) and the false cursor was at (824, 656)? Do the false cursor positions always have a relatively small pressure value?

Regards,

Nick

0 user5926475 over 5 years ago in reply to Nick Saulnier

Expert 1270 points

Hello Nick,

Yes, the correct location was (233,609), (824,656) is the false cursor position.

We do the test for the false cursor appear several times, it is true that the false cursor position have a relatively small pressures value.

Best Regards

Dudechao

0 Nick Saulnier over 5 years ago in reply to user5926475

TI__Guru** 102640 points

Hello Dudechao,

Please take a look at tslib's filters to see if any of them are of use. E.g., small pressure values could be filtered out with https://github.com/libts/tslib#module-pthres . There are a couple of other filters (like debounce) that might be helpful.

Regards,

Nick

0 user5926475 over 5 years ago in reply to Nick Saulnier

Expert 1270 points

Hello Nick,

Many thanks for your support.

We filter out some values with tslib and it works as expected.

Regards,

Dudechao

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PROCESSOR-SDK-AM437X: 5-wire touchscreen issue