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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
Ok, try again now. I've found the problem and updated the Original Espruino's image with the fix.
Turns out it was to do with the Low Speed oscillator. The F1 behaves very slightly differently to the F4, and the startup code got stuck waiting for the RTC to initialise - unfortunately if you previously had a good firmware on the device then when you put the new one on everything will keep working until you power it off (as the RTC is already set up).