You are reading a single comment by @Gordon and its replies.
Click here to read the full conversation.
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.
@Gordon
BOOT1 is pre-grounded, so all you have to worry about is BOOT0, which is available on the BTN/B0 Jumper. If you short that out, then when you press the button and apply power (or reset) the board will go into bootloader mode.
Normally, the bootloader is a custom one that uses a USB UART, but with BOOT0 to 0, you get the ST bootloader which does DFU USB and UART. All you need to do is make sure USB isn't connected, and then it'll be available on serial.