Flashing custom firmware (MINI)

Updated 1 month ago ​by Martin Lexa

We take safety very seriously. Before being released, every firmware version goes through intense testing to verify that all features work as they should. That applies especially to the safety features: for example, if the thermistor readings are outside the limits, the heating stops automatically to prevent any possible damage.

We cannot guarantee the functionality of the safety features in a community-made or custom-modified firmware.

Our official Original Prusa MINI firmware is signed with a private key, and the printer verifies the validity of this signature before it allows a firmware update.

To flash your own (or a community-made) firmware to your MINI, you’ll have to break the appendix on the logic board (called the Buddy board) and move the jumper to the correct position. Breaking the appendix on the Buddy board is irreversible and voids the warranty of your printer’s electronics.

After you break the appendix, we disclaim responsibility for any possible damage done to the printer and/or its surroundings (e.g., in case of a fire).
  1. Turn the printer off and open the electronics box.
  2. For more clarity, the board on the photos is taken out from the casing, but you don't need to do that.
  3. Locate the power switch on the Buddy board. The appendix is underneath it, so you have to pull the switch out to access the appendix. The switch is held in place by a safety pin on both sides of it, push the pins together so that you could move with the switch.

  1. Take the 2 mm (or similar) hex key and use it as a lever to carefully break the appendix. Be very careful; don't break anything else on the board. Use the pliers to remove the broken appendix completely.
  1. Check the five pins next to the orange "PRUSA Buddy" inscription on the board. There should be a black jumper on two of the pins. Move the jumper from its current position to the three pins above the broken appendix. Put it on the two pins that are closer to the center of the board. Leave the third pin empty.
If the jumper is missing completely, you should have received a spare one from us via the mail.
  1. Snap the power switch button back into its original place and close the electronics box. You can now flash any firmware to your MINI's Buddy board.

If the jumper is not present or if it is placed incorrectly, the printer screen will be blank (as shown below) after you turn it on. Turn the printer off, double-check the jumper position and turn it back on.

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