Success! My SC31 Pro now runs Anduril 2. Flashed without removing the driver!
It was surprisingly easy. First I removed the switch bezel, the silicone switch cover and pulled out the switch PCB to have a look at the driver. The wires are long enough. The MCU is located right in the middle of the big hole – how awesome!
So I made a little jig to update the firmware. A 4-pin pogo-pin adapter to contact pin 5-8 (MOSI, MISO, SCK and VCC). Without a matching PCB (0.05” pitch) this was the hardest part. My final solution was to use a ribbon cable (comes in 0.05” pitch), crimping the pogo pins onto the ends and glue everything to a piece of plastic. After the glue has dried, I covered everything in hotglue and heat shrink tube (that’s my usual way of making custom adapters). RST was hooked right into the leg and GND was the easiest: Just clamp it between the head and the battery tube.
Now that everything was in place I connected the programmer and my laptop, built the latest version of Anduril 2 with the SP36 config (which is used by Sofirn for all of their Anduril flashlights) and hit return.
Everything went well, so I could remove all wires and put the switch back together. Done, Anduril 2 update on the SC31 without removing the driver.