micropython-samples/fastbuild/pyb_boot

#!/usr/bin/python3

# Called from buildpyb
# Put pyboard into DFU mode.

import sys
import os
mp = os.getenv('MPDIR')
device = os.getenv('MPDEVICE')
sys.path.append(''.join((mp, '/tools')))
import pyboard
def main():
    pyb=pyboard.Pyboard(device)
    pyb.enter_raw_repl()
    try:
        pyb.exec_raw('pyb.bootloader()')
        print('Failed to enter DFU mode')
    except Exception:  # It will throw one!
        pass

if __name__ == "__main__":
    main()