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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.
@Gordon
The STM32F1 doesn't have a USB bootloader, so you've got to flash it either via the SWD/JTAG pins, or using the serial bootloader.
There are already some instructions on using the Serial Bootloader here, which should help you out: http://www.espruino.com/Serial+Bootloader
Espruino on the F1 (and F4) has its own bootloader, which is how you can flash it from the Web IDE :)