Apparently some fab houses can do firmware programming and testing of the devices right in the factory — you just have to provide detailed step-by-step instructions on how to do it. So I started work on the firmware flashing guide and on the test program. I also modified the version 8 PCB design that I have on order from Aisler to add the VCC pad to the bottom of the board — together with SWDCLK, SWDIO and GND they form the programming interface. The STLink clone I had didn't require VCC connected, but it also didn't program the chips consistently. The J-Link is consistent, but requires VCC to drive its own programming pins.

I'm also working on the guide itself, and one of the things I will need is a drawing of the board with the pads marked. So I made this:

I still need to write the actual test program, and see if I can somehow put the CircuitPython and the bootloader into a single binary to be flashed — that would simplify and speed up the process. Unfortunately the test program will still need to be copied over USB — because I also want this and the flash chip tested.