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Topics - vpd

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TFTs / Capacitive touch problems under linux (FT5x06)
« on: July 02, 2014, 04:46:12 PM »
Hi,

now we are prototyping couple of devices using TI AM3358 Starter Kit. (http://www.ti.com/tool/tmdssk3358)
Original kit goes with resistive touch but we purchased couple of displays with capacitive touch from digikey:
1) NHD-7.0-800480EF-ATXL#-CTP
2) NHD-4.3-480272EF-ATXL#-CTP

Then we tried several FT5x06 drivers found on internet. One driver was good enough to work with touch screen. Most of them failed due to firmware version mismatch. However, several problems still exist.

1) Now driver works only with 7" display. 4.3" does not. Driver recognizes both displays via I2C, handshakes, etc. but in case of 4.3" there are no interrupts from FT5x06 during touch activity. We tried 3 different 4.3" displays from one purchase and result is the same. Then we supposed that driver has set touch threasholds too high so it does not recognize events. We tried to write different values of amplifier via the linux driver but this does not help. So, 4.3" touch does not work even without any glass.

2) Display of 7" works if direct touched but does not when placed beyond 4mm glass. Similar to item 1 we could not find solution how to improve sensivity.  We see in linux kernel log that 7" and 4.3" displays report slightly different descriptors during handshake. Now I cannot remember exact phrase but something about different number of rows in matrix.

Is there any guide how to set up touch controller settings to force it to work? We actually need it to be placed beyong glass as thick as 2 mm (or even 4 mm).

Best regards.

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