In between playing Doom on the most ergonomically challenged devices, [Aaron Christophel] likes to take a relaxing break with reverse-engineering Xiaomi Mi Band fitness trackers and writing custom firmware for them. Also so that he can play more Doom on those, natch. The latest subject comes in the form of the Mi Band 10, which features a BES2700iMP SoC, known internally at the manufacturer Bestechnic as the BEST1503. This is all documented on the GitHub project.

In the accompanying video we get some more details on this project, with the main challenge being that for this Mi Band 10 there’s no public SDK for its SoC. This was a major bummer until [Aaron] realized that the BEST1306 (BES2700IHC) is effectively the same SoC, but with a leaked SDK available via apparently audio-focused development kits. From there a BEST1503-compatible SDK could be assembled.

Naturally, to check that all of this was working correctly Doom was ported to the device courtesy of the GBADoom project. This mostly works aside from the display running in single-bit SPI mode instead of quad-SPI that it should be capable of, along with limited color depth. Despite burning all the tokens on the Claude, this provided little help, probably because the required information hasn’t leaked out of Bestechnic yet and ended up in the training data set.

Since the Mi Band 9 uses the same SoC, it’s expected that this reverse-engineered SDK will also work for that fitness band, though that hasn’t been tested yet.