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Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
@Jean-Philippe_Rey
OK problem solved.
I realised the reason the bootloader wasn't working is that I accidentally made a permanent solder bridge between D0 (BTN pin, used by the bootloader) and VCC.
I just removed the solder bridge and now the bootloader works well. I was able to update the latest FW (2.05) with DFU.