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Flashing custom firmware

(MINI/MINI+)

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MINI
MINI+
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Every firmware version goes through intense testing to verify that every single feature works as it should. That applies especially to the safety features: for example, if the thermistor readings are outside the limits, the heating stops automatically.

Official 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) unsigned firmware, you’ll have to break the appendix seal on the Buddy board and move the jumper in the correct position. 

  1. Turn off and unplug the printer.
  2. Pull out the power switch to access the appendix (1).
  3. Take a small thin screwdriver, insert it into the long hole furthest from the wall of the case, and carefully remove the middle part.

  1. Check the three pins above it - there must be a black jumper on the two pins that are closer to the center of the board.
Some revisions of the board will only have two pins for the jumper. You will then not need the jumper at all! Only break the appendix seal to flash unsigned firmware. A jumper on these pins can even prohibit the firmware from being updated.
Breaking the appendix seal won’t void your warranty, so you are free to flash custom firmware.
However, since there is no way for us to verify or test every single custom firmware on the internet, we disclaim liability for any kind of damage or harm a printer with a broken seal may cause (e.g. in case of a fire). 
So, please, don’t mindlessly flash suspicious files! 
 

7 comments

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RosePeach
Please create a similar guide for the MK4.
RosePeach
Can official Prusa firmware releases still be installed after breaking the appendix?
Giuliano - Official Prusa CS
Hello. Yes, official firmware releases can be still installed.
stefanct
I just want to note that the jumper's reference is J1. It's visible in the image but not mentioned in the text and thus not discoverable by search engines. Now it is ;)
meermanr
How does each step alter the behaviour of the printer?
For example, my educated guess is that breaking the indicated PCB section disables firmware verification - so I can compile and load a firmware myself using the usual method (by placing a .bbf file on a USB Mass Storage device and rebooting), while moving the jumpers places the board into a reflashing mode so I can connect it directly to a laptop to ... use what software to talk to it? And what would the laptop and board talk about?
Personally, I just want to change a #define of the official firmware, compile it, and flash it on. If the printer no longer boots after making this change then I wouldn't want to undertake it.
Clarifications would be greatly appreciated.
MrTeliP
I have this version of the Buddy Board with the three pins and I have finally decided to Klipperize my Minis. I'm running into a problem where I have broken the appendix and moved the jumper to the 2 pins shown (I have the 3 pin version), but it just boots up like normal and does not enter DFU mode. Any suggestions? I'd really like to get these running Klipper like all my other printers.
William H. - Official Prusa

Tried without the jumper?

MinnesotaMean
If you haven't figured it out yet, the picture above is incorrect, to enter DFU mode you need to put the jumper on the leftmost two pins. You'll know that DFU mode is enabled when the screen turns white. It'll then show up  as an DFU device on whatever device you have it plugged into. If you're using Windows, be sure to install dfu-utils.