Touch sensor

[marijnvdwerf]

Based om the 0x90 and 0xD0 you discovered to return the touch position, it seems like the touch controller might be an XPT2064 (or ADS7843?). The 16-bit values you described actually seem to be 12-bit values, with 4 wait cycles before it. Your 0x16 for Z seems to match the command used for getting z1, just shifted by some bits.

https://ldm-systems.ru/f/doc/catalog/HY-TFT-2,8/XPT2046.pdf

[nviennot]

Amazing!
I can't find the 0x90, 0xD0, 0x16 references in the datasheet. Where did you cross reference them? Did you find any documentation?
Do you have a 3d printer?

[marijnvdwerf]

I found the (likely) chips by Googling 'touch screen spi 0x90 0xD0'.

As for the control byte; the marked references below should make that clear: (Using the datasheet for the ADS7846, since it's a bit neater. Table 4 and 5 on the XPT datasheet use the same caption, whereas on the ADS sheets they differ)

	ADS7843, ADS7846	XPT2046
Control bits	Table III, IV	Table 6, 7
Channels	Table II	Table 5

Also datasheets for the original chips:
https://www.ti.com/lit/ds/symlink/ads7846.pdf
https://www.ti.com/lit/ds/symlink/ads7843.pdf