Cheap 3.5" screen with touchscreen.

[AndyA]

Want to add a touchscreen to your small display? The chances are you already have one and just don't know it.

I posted previously how to convert this http://www.amazon.co.uk/gp/product/B0056WJP1M display to run from 5V rather than 12V.

I was in the process of repackaging it into a smaller case when I discovered that if you remove the plastic face plate the display already has a a 4 wire resistive touchscreen bonded to the front.

This touchscreen seemed to be pulled out to pins 4-7 of the display ribbon connector and from there to pins 33-29 of the display driver IC.
Pin 1 of the display connector is the end nearest the display driver IC. The display driver IC is 48 pins, the side facing the connector are pins 25 to 36.

So we have the a 3.5" display with touchscreen connected to a driver IC of some sort all for under £20 or under $20 in the USA.

Unfortunately this is where I hit a brick wall.
The display driver IC appears to be an MST702-LF, so far I've been unable to locate any datasheets for this part in order to see firstly if it can indeed drive the touchscreen and if so if there is an easy way to hook it up to the RPi board.

Maybe someone else here will have better luck than me at digging up some information.

[AndyA]

Update to account for my inability to count in the correct direction:

I had the display ribbon cable back to front, pin 1 is the end one furthest from the driver IC, closest to the power supply and buttons.

It looks like the touchscreen pins aren't connected to anything and are just floating.
So it'll take a touch screen controller (or an ADC and some software) and some fine but possible soldering to make use of the touchscreen.

[aaa801]

This is probably what your looking for

http://wenku.baidu.com/view/a5d88b00cc1 ... 20829.html

direct link (signing up for a acc to get the file is a pain)
http://uppit.com/tgu6peco5pol/MST702.pdf

[shinji2009]

aaa801

can you please reupload datasheet?