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I'm required for a project to have a 2mm glass shield over the official 7" touchscreen. With it in place, I obviously can't detect touch any longer (except when using 2 fingers at the same time but it is inconvenient)

Is there a clean way - Without having to fiddle with FT5406's internal I2C registers - to set the sensitivity of the touchscreen ?

I took a look at the driver, but there don't seems to be any parameters I can set: 

pi@raspberrypi:~ $ modinfo rpi-ft5406
filename: /lib/modules/4.4.21-v7+/kernel/drivers/input/touchscreen/rpi-ft5406.ko
license: GPL
description: Touchscreen driver for memory based FT5406
author: Gordon Hollingworth
srcversion: BFF35BF70365F2D3908ADB5
alias: of:N*T*Crpi,rpi-ft5406*
depends:
intree: Y
vermagic: 4.4.21-v7+ SMP mod_unload modversions ARMv7

Thanks

EDIT: After some investigations, it seems that the display version i'm using is 1.1. It uses a FT5426 touch driver chip which explain why I was unable to mess with the I2C register (The register datasheet for the FT5426 isn't available and it looks like it works differently from FT5406). FT5426

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4
  • I don't think you can change the sensitivity of the touch screen. How mandatory is that 2mm of glass?
    – Jacobm001 ♦
    Jan 24 '17 at 17:31
  • My google fu has deserted me, and I'm struggling to come up with a reference to confirm that the chip in the 1.1 is the FT5426 - could you point me in the right direction?
    – goobering
    Jan 25 '17 at 0:10
  • @jacobm001, sadly, like mandatory mandatory
    – DeadlyJesus
    Jan 25 '17 at 10:07
  • 1
    @goobering, give me second, i'll unpack my raspberry and take a picture
    – DeadlyJesus
    Jan 25 '17 at 10:08
1

Okay I managed to solve my problem, it's a bit tricky but I might as well post it here.

Changing the sensibility on the official 7" display turned out to be (as far as I know) impossible. So I tried an other scren from waveshare (7" HDMI LCD Rev 2.1).
Turns out you can't change the sensibility on this one either BUT I found this tutorial from psyco68 on how to install his open source firmware for the touchscreen. Be warned, it requires a bit of hacking and soldering.
I followed his tutorial, only changing these two values in gt811.c : 

// [53] The screen key threshold
// 0x50,
0x09,
// [54] Screen loose threshold
// 0x30,
0x05

I flashed the screen with the freshly compiled firmware and its now working with the 2mm shield over it. Hope this can help someone ;)

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It looks like the sensitivity of the touchscreen is not able to be changed as it is controlled by the hardware. To fix it you could change the 2mm of glass to 1mm or 1.5mm or you could buy a more sensitive screen. Hope this will help and good luck.

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