Rumpel firmware update

1. Connect the device to this computer with USB. If its status shows CONN (USB drive), eject the drive first or press 3, so the port is free.
2. Choose a version and press Flash, then pick the port USB JTAG/serial debug unit.
3. Wait until the log says done; the device restarts with the new firmware. Settings on the SD card and stored WLAN passwords stay.