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Author Topic: Capacitive touch screen calibration  (Read 473 times)

T.Pierret

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Re: Capacitive touch screen calibration
« Reply #15 on: June 18, 2020, 04:02:29 PM »

Hi.

No. The calibration process has been successfully done at the beginning of the tests session.
During the tests sessions, 0xF... values have been read for one of the touch coordinates from the REG_TOUCH_SCREN_XY register, while the touch happens at the edge of the screen.

Regards.
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T.Pierret

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Re: Capacitive touch screen calibration
« Reply #16 on: June 19, 2020, 11:41:23 AM »

Hi,

Today the trouble has been observed several times again. I can provide more data.

Touch transformation matrix (after calibration through CMD_CALIBRATE):
Code: [Select]
0x0000D9AA 0xFFFFFEFD 0xFFE5CC8C
0xFFFFFE4C 0xFFFF7696 0x0208B092
If the translation is correct, here are the float values:
Code: [Select]
0.85025 -0.00395203 -26.201
 -0.00665283 -0.536774 520.69

Here is the recorded touch:
Time SmoothStepReadTagPressure
2957065529,17765529,1770143
2957665521,177311,36601043
2958265513,177333,3570983
2958765508,177343,36916872
2984654657,200336,32016583
3010445664,206271,239161328
3036221878,22332768,327681632767

Hoping this may help

Regards
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BRT Community

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Re: Capacitive touch screen calibration
« Reply #17 on: June 22, 2020, 12:26:58 PM »

Hello,

It seems like your other post regarding tags may be related to this.
http://www.brtcommunity.com/index.php?topic=147.0

The calibration on the screen should affect the tagging and track properties on the screen equally. Its possible that this behaviour could be related to the CTP as it might jitter between coordinates slightly and so eve might see coordinate inside tag and then outside, etc.

Would it be possible for you to create a simple example which exhibits the behaviour you are seeing?
e.g. can we see it by just drawing a rectangle and tracker on it and a small tag number printed beside?
This should help narrow down where the issue might lie.

I would appreciate if you could email this example into: support.emea@brtchip.com, along with a description of the symptoms you are seeing. We can then try this on some hardware here to further the investigation into this behaviour.
We can post the resolution here for any interested parties.


Best Regards,
BRT Community
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T.Pierret

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Re: Capacitive touch screen calibration
« Reply #18 on: June 22, 2020, 01:29:33 PM »

Hello,

OK. I will try to provide that  :P. I'm not sure I will get the time for since the decision about the screen controller to be used should fall soon.

To summarize our observations: the tag value (read from REG_TOUCH_TAG) is nearly always 0 for the first readings (let me say within the ~20 first milliseconds of the touch). Within this delay, the touch coordinates are also observed shifting.

For info, the touch registers are read in a single shot: 5 registers from the REG_TOUCH_RAW_XY address. Could this be a problem ?

In a general way, how is data consistency guaranteed while the touch registers are continuously polled ?

Many thanks for your support.
Regards
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T.Pierret

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Re: Capacitive touch screen calibration
« Reply #19 on: June 23, 2020, 03:08:08 PM »

As suggested, the mail has been sent to the support with some test code.
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pauljiao

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Re: Capacitive touch screen calibration
« Reply #20 on: June 24, 2020, 02:45:12 AM »

For calibration process of capacitive touch screen, it shall be done in compatability mode (single touch) only.

It is not possible to do the calibration at the extended mode.

So to read the final touch point coordinate (after the calibration process),  REG_CTOUCH_TOUCH_XY at address 0x302124  shall be read.  The coordinate before the calibration process is stored to REG_CTOUCH_RAW_XY at 0x30211c.   

These are what I understand from programming guide.
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T.Pierret

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Re: Capacitive touch screen calibration
« Reply #21 on: June 25, 2020, 07:47:07 AM »

Hi,

Thanks for your answers.

The issue is solved by using data from the REG_TOUCH_TAG_XY register instead of those from the REG_TOUCH_SCREEN_XY. When the coordinates are weird in REG_TOUCH_SCREEN_XY, the data in REG_TOUCH_TAG_XY are invalid (0x8000 value) and can then be ignored. In this way, many touch information are ignored but at least, the touch can be correctly managed to get the expected behaviour.

@pauljiao
We have ordered a capacitive screen for comparison. The info you provided shall be taken into account. Thanks.

Regards.
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