A friend bought one of those fake Apple iPad clones, that actually run android, in China and brought it with him. The thing even has the Apple logo on the back and all. Turns out that it's bricked because no touch input is accepted.
I've opened the thing up and found a 4-wire resistive touchscreen. It is read by some vague IC from a Chinese semiconductor company, that is controlled over SPI.
Chip is "SEMCO CS7146", i found a Chinese datasheet if anyone's interested.
Now I'm trying to pin point the actual problem, but i have no experience with resistive touchscreens. I do have a bit of experience with capacitive touchscreens though.
I'm measuring the resistance across the X and Y terminals, but it doesn't seems to change when I touch the display. Can i assume the foil is damaged ?
In idle condition (jitters a bit when touched) :
Resistance across X terminals : 731 Ohm
Resistance across Y terminals : 240 Ohm
I guess i could hook up a logic analyzer to the SPI bus and look at what it's reading, but i thought I'd check here first for some insights on resistive touchscreens.
So, shouldn't the resistance change when i apply pressure on the foil ? Or is the difference very small perhaps ?
I also found AVR341, which has example code to read a 4-wire resistive touchscreen, but since i have no experience with these foils, and i don't know if the foil is damaged or not, this route might be a waste of time.
It would be nice if I could get any use out of this device, except as a coaster, since it's actually a pretty neat thing.
Perhaps I can hook up an USB mouse to the thing, but i'm not sure if the android OS has a default driver for this.
Any insights or tips are appreciated. Thanks.