PW 1.8V voltage reference on a PW?

I have a defunct PaperWhite (probably, the serial number's inaccessible). I'd like to connect up a UART to see if anything comes out and possibly try to get some use out of it that way.

I have the appropriate TTL to USB adapter, but mine requires a 1.8V voltage reference for the low-voltage side (it'll work with any reasonably low voltage). I could try and produce that from my bench power supply but it'd be so much easier if I could source this from the Kindle itself. Before I go poking at test pads to see what comes out, has anyone else managed to figure this out?

Thanks!