What was done
tomekent used Claude to map the pins, chips and drivers of a Yoto Player Gen 2 and write firmware that turns it into an Audiobookshelf player.
tomekent built yotwo, custom firmware that turns a Yoto Player Gen 2 into an Audiobookshelf player, with a lot of help from Claude. His own description says that covered the code and also working out the hardware: the pin map, the display driver, the NFC reader and the charger lines.
How it was done
The author backed up the original firmware and studied it to learn how the board is wired. Claude wrote the journal of the work as it went. The pin map and chip list were learned from the original firmware's own hardware description, then confirmed one by one as yotwo's drivers brought each part up on real players. The Gen 2 uses an ESP32. Secure boot and flash encryption are off on both boards checked, and the README says no security measures were bypassed. The notes on the original firmware are not published, and the firmware is written from scratch with none of Yoto's code.
Results
The player browses a whole Audiobookshelf library with its two knobs, with no cards and no cloud. It adds favourites, background downloads, optional NFC card linking, a sunrise clock, a web page on the player and over-the-air updates with roll-back. It is in daily use on two players and is marked beta. Installing needs opening the player, soldering five wires and a serial adapter. The repo includes a desktop simulator of the 16 by 16 display.