capacitive touch on NHD-5.0-800480FT-CTXL-CTP not working

NormanWerner79

I am evaluating NHD-5.0-800480FT-CTXL-CTP for a new development.
We use a NHD-5.0-800480FT-CTXL-CTP  with FT813 and control it via custom STM32 based board.
Basic API seems to work. Basic graphic seems to work as well.
 
However capacitive touch does not work at all. CMD_CALIBRATE will show a “dot” but will not detect any touch events.
Upon further investigation I found , that CTP_RST#  (which is connected to reset of capacitive controller) is constantly low.
Reading REG_CPURESET yields 0x00.

"Sometimes" touch will work upon restart (like 1 out of 10 tries). Any help is appreciated.

Best Regards
Norman

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  • NormanWerner79

    After further investigation I can report some more details:

    I ordered Board (Rev. 1.0) via mouser in 07/19
    In rare cases (like 1 out of 10 tries) capacitive touch will work after powering up.

    After tying CTP_RST# low via soldering I can see, that the touch controler seems to work fine every time.
    However FT813 will not respond to generated interrupts.  Only in rare cases everything will work after powering up.

    I suspect a problem with FT813 powering up. I tried different methods of Powering of (timing of PD-Pin, ACTIVE command or CPURESET) - no luck.
    One more hint: I have to use the command ACTIVE two times (as indicated in the datasheet). However all sample code only uses one such call.

    Best Regards
    Norman

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