HSI is out of spec for reliable USB operation, even though it sometimes works. stm32-h103 board has an 8Mhz external crystal which should therefore be used for any USB work. Originally reported as https://github.com/libopencm3/libopencm3-examples/pull/192
README
This example implements a USB bootloader for the Paparazzi project.
TODO: Move to examples/lisa-m?