Input: Focaltech ft5336 sends events when no touches present.

[glenn-andrews]

The FT5336 has a register REG_TD_STATUS that determines the number of touches on the panel when polled.

Currently the code checks if zero or one touches are present, then reads 4 bytes of coordinate and status information. If there are no touches all four coordinate bytes are zero.

The problem is a touch event of 0b00 is considered 'pressed', so when there are no touches, the driver thinks someone is continuously pressing on the screen at coordinates (0,0)

I believe one solution is to change line 106 of drivers\input\input_ft5336.c

From:

pressed = (event == EVENT_PRESS_DOWN) || (event == EVENT_CONTACT);

To:

pressed = ((points == 1U) && ((event == EVENT_PRESS_DOWN) || (event == EVENT_CONTACT)));

I've tested this using the Adafruit 2.8" touchscreen (https://www.adafruit.com/product/1947) and it appears to work.

A better solution would be to refactor the ft5336_process() so it only reads the coordinates if the number of touches is 1, to reduce I2C traffic.

[glenn-andrews]

Fixed by #69998