Author Topic: Touchpad made from touch screen sensor?  (Read 2228 times)

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Offline mrdunk

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Touchpad made from touch screen sensor?
« on: Mon, 06 July 2020, 12:18:16 »
Has anyone played with this sort of thing?
https://www.aliexpress.com/item/32919184847.html?spm=a2g0o.detail.1000023.23.78db112896fZF7

TLDR: It's the capacitive sensor from a touch screen.
They are available in all different sizes, track multiple simultaneous touches, have i2c interface and are relatively inexpensive.

Seems someone has already done the hard work of getting this to play with Arduino:
https://github.com/nik-sharky/arduino-goodix
Also source for Android and Linux is available so any gaps in that would be easy enough to reverse engineer.

If anyone want to go the easier route, the one linked above actually comes with a USB converter...

I'm thinking a touchpad made from this mounted on 4 nice clickey buttons so pressing it gives an oldschool mouse type click....
hey, its transparent so no reason you couldn't put a screen under there as well with nice patterns showing where you are pressing...

Offline mrdunk

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Re: Touchpad made from touch screen sensor?
« Reply #1 on: Wed, 08 July 2020, 17:46:00 »
huh.
Here's someone else with the same idea:
https://github.com/Staars/BT-TrackPad-ESP32

Offline Leslieann

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Re: Touchpad made from touch screen sensor?
« Reply #2 on: Wed, 08 July 2020, 21:17:41 »
Not a silly idea on the surface.

It could work, but they often have terrible accuracy and sensitivity, they also often lack multi-touch.

You will probably also need to disable the location part of it, remember these are designed to cover the screen and be location accurate, i.e. top left means top left of the screen, while a touchpad operates more like a mouse, it's location on the screen/pad is agnostic, so long as you hold the button you can lift your finger and move to the side to keep sliding multiple times. I hope that makes sense, in some systems you can disable this, but not always.
« Last Edit: Wed, 08 July 2020, 21:19:56 by Leslieann »
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Offline mrdunk

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Re: Touchpad made from touch screen sensor?
« Reply #3 on: Thu, 09 July 2020, 18:36:06 »
The one i linked to in my first post does multitouch.
As long as it can return location data of touches, calculating movements from that is a programming problem rather than a hardware problem.

Accuracy would be an issue... but motions could be smoothed in software, providing the resolution was adequate.
For a mouse average movement over a 50ms window is more important than exact coordinates on each update.

Sensitivity though...
Not much we could do if the resolution was poor.

Offline mrdunk

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Re: Touchpad made from touch screen sensor?
« Reply #4 on: Thu, 09 July 2020, 19:03:21 »
Here's one that actually states resolution:
https://www.aliexpress.com/item/32891241415.html?spm=a2g0o.productlist.0.0.7d1f10eceEZrNz&algo_pvid=0c1c25fa-4262-45f8-b36d-4d609931688d&algo_expid=0c1c25fa-4262-45f8-b36d-4d609931688d-0&btsid=0ab6fa7b15943377080342283e6d0b&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
Code: [Select]
800*480 Resolution
Not terrible.
I wonder if that's average for these GT911 driven displays.

According the the GT11 datasheet ( https://www.crystalfontz.com/controllers/GOODIX/GT911ProgrammingGuide/478/ ) the coordinates are a 16bit number which would imply a /maximum/ resolution of 6k.
Nothing on there to hint at a normal example though.

Trying to resist the urge to buy parts for another project that i don't have time to finish...