- Jumper the device to start into the serial boot loader, connect the UART to an off-board USB-UART adapter,
- Run the well-known python tool for downloading just as you would with the dev board.
Or get the chip to tristate the flash pins, contact them with something else and directly write the flash.
Or program the flash chip before soldering it in place.
Next time around have a connector, edge fingers, or pads for a pogo-pin spring contact jig.
#After Sales #PCB Assembly