AW: multi-touch?

Joerg Reisenweber joerg at
Fri May 30 16:06:11 CEST 2008

Am Fr  30. Mai 2008 schrieb Fabian Off:
> Hey!
> How does synaptics handle this? When I look at the output my touchpad does, 
I can see "X Y Fingers" Values... Maybe we could look into this code and see 
how they do detect the amount of fingers? Dunno whether they work nearly the 
same, but I believe this could maybe point us into the right direction :)
> Only my idea... 2-finger-scrolling is so great!

To the best of my knowledge, at least MY synaptics in front of me right now is 
a capacitive type, and even this one doesn't support multitouch right now 
(though maybe a driver issue). 
Please google or wp for capacitive vs resistive ts! Our 4-wire resistive type 
ts is a device as dumb as bread, NO silicon inside. You simply can't do muto 
with such device in a reasonable straight way. How do you get info of 
X1,Y1,X2,Y2 out of a device with 4 ANALOG connectors (GND incl!)??? It may be 
feasible, but it's rather tricky and needs quite some special hw AROUND the 
silicon-free ts. 
There's a way to detect the "surrounding square" of _all_ touchpoints on a 
4w-R-ts, at least with GTA02 i think. You may use this to detect there's more 
than one touchpoint. Still you have no correct data for the coords of the 2 
(or 3?) points.

Maybe eventually I'll write a little article on it - so I don't have to repeat 
myself all the time ;-)

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