How to flash a split mechanical keyboard

This is a reminder guide for myself on how to flash a split mechanical keyboard. In my case this for a Scylla Bastard Keyboard

  • Firstly setup the config at
  • You can upload an existing json if you have one to continue where you left off
  • Once done, on that same page you can compile and download the firmware to disk
  • Download and install the binary QMK Toolbox
  • Disconnect the keyboard AND the cable that joins the two halves of the keyboard
  • Open QMK Toolbox we just installed
  • Plug in only one half of the keyboard, we will flash the other half later
  • Press the reset button on the underside of the keyboard
  • Click “Flash” in QMK to start the flashing process. Do not disconnect the keyboard until the process is complete
  • Disconnect the first half, and connect the other half
  • Repeat the above steps to flash the second half
  • Disconnect the keyboard then plug everything back in as normal
  • The keybaord configuration can then be tested at