Touchscreen offset and calibration

[Simon Bagley]

I am porting the touchscreen driver for use on a TI DM3730 based board with Android ICS 4.0.3, which uses a four wire resistive touch panel on top of a WVGA (800x480) LCD.

The board uses the TSC2046 touchscreen driver IC which operates in the same way as the ADS7846, hence we are using the ADS7846 driver files.

The problem I am experiencing is when I touch the screen, the touch location is offset from my touch point in the Y axis (shorter axis, as in landscape orientation). I can add an offset to the reported y value, in the ADS7846.c file, just before the call to input_report_abs(input, ABS_Y, y), which solves the offset problem, but I don't think this should be necessary. I have modified the ads7846_probe() function to use the logged xmin, xmax, ymin, ymax values for my particular board and touchpanel combination. These are reported in the calls to input_set_abs_params(...).

Why is the y pointer position offset from my actual touch position?

I have read in the Android AOSP documentation that .idc file is needed, but where should this be located so it gets included in the built filesystem?

[Gary Bisson]

Hi Simon,

You can look at the grouper device folder as an example:

http://androidxref.com/5.1.1_r6/xref/device/asus/grouper/raydium_ts.idc

Once you've created your idc file, you just need to add it in the PRODUC_COPY_FILES as follows:

http://androidxref.com/5.1.1_r6/xref/device/asus/grouper/device-common.mk#70

Hope this helps.

Gary

[Simon Bagley]

Hi Gary,

thanks - I now know how to get the idc file included.

Regards,
Simon