resistive touchscreen

Resistive touch screen just needs two ADCs that detect two resistance values (for X and Y). Resistance values are then converted to screen coordinates by means of calibration data (to get calibration data, user has to launch a procedure that shows crosses in the four corners of the screen).

That said, the connection circuit is easy to implement

microcontroller - Resistive Touch Screens - Electrical Engineering Stack Exchange

On Linux (and hence android) you can find several touch drivers. The most widely used is tsc2004. You can have a llok and start from there

Ambrogio

Thank you Ambrogio. I understand the x and y aspects of a touch screen. I just don't understand how to get this data to android. A driver would mean there is a device to connect to convert the data to something the android understand by utilizing the driver. When i try to google touchscreens all it shows is a 10 inch and a 5 inch with a capacitive sensor. My problem is i can't fit a 10 inch in my dash and 5 is just too small.

Does anyone know what i need to do in order to connect a 4 wire touch sensor to the riotboards gpio and what source to edit in order for it to work? Or perhaps a usb device that works with android since the ar1100 does not.

edit: well i can't figure out how to communicate with the ar1100 when it's connected to the android but i did figure out that i can send commands to emulate touch/ tap events from the shell

input tap 200 622

so for now i am going to use a arduino to "read" touch events and then send them to the shell. Once i figure out how to edit the source to read the sensor over gpio then i will modify the source to read the events directly. For now i will use the debug port

Hi

I would start from an existing touch screen driver like this one

https://gitorious.org/var-som-4x/ics-3-x/source/30bbe8cc47f64b29570f0f0ef718e40ef933e98d:drivers/input/touchscreen/tsc2004.c

This controller has a I2C interface so you should use it just to understand how the driver integrates in the while system (have a look also here http://processors.wiki.ti.com/index.php/Capacitive_touch_integration_with_android)

Then I would change the functions that access the I2C to read directly from the ADC

Regarding physical connection, I would connect the X and Y terminals of the touch screen to the connector GPIOs (hopefully they can configured as ADCs...)

Ambrogio

I had exactly the same problem.  By default the AR1100 enumerates as a HID mouse with a vendor:product code of 04D8:0C02, as your debug output shows.  What you need to do is install the Microchip AR Configuration Utility on a Windows PC, plug in the AR1100 and your HDMI screen, and use the Manual Setup utility to change the mode to DIGITIZER.  Now when you plug it into your Android device it will enumerate as 04D8:0C03 and work as expected.  See here for more info.