Can't flash firmware

Trying to flash firmware but getting nothing from the board…

Things to check:

  • The first time we burn firmware to a new board, we need to manually put it
    into boot mode by holding button 2 and momentarily pressing reset
    (otherwise, although the OS sees the port, esptool will not be able to write
    to it); sometimes the device goes back into that state (or is in a bootloop
    that prevents upload), and requires the same hold button2/touch reset
    combination to fix.
  • Note also that the unphone9 port will usually appear as /dev/ttyACM0 in
    ubuntu; sometimes it shifts over to ACM1 or ACM2 when resetting, so if
    encountering problems writing to the board try changing the port (and/or the