Firmware updating & flashing problems

Updated 1 month ago ​by Tomáš Chvalina

Always check if the new driver package is installed before flashing the newest firmware. That can be checked in Prusa3D drivers page. Before doing any following steps, double check that you have followed all instructions in the Firmware upgrade and flashing article precisely.

There also a chance that any of the following problems was just a "one time bug". Therefore, we suggest trying to do the normal firmware update again, just to make sure. 

Most common updating & flashing problems

  1. Unplugging the USB cable before the Firmware update is fully finished - Make sure that the firmware update is not interrupted in the middle of the process. Do not unplug the USB cable before FirmwareUpdater says that the process was successfully completed.
  2. Timeout error - FirmwareUpdater is not getting a response from the miniRAMBo or EINSY RAMBo board. Check that your printer is powered on. Next step is to check your fuses, you can visit this article for more information, Blown Fuse (miniRAMBO).
  3. Uploading different file, but .hex "Wrong file has been selected for flashing". Make sure to unpack the archive with firmware and select the .hex file for your printer model.
  4. Avrdude.exe - FirmwareUpdater was not able to find the proper COM port. In order to go over this problem. Follow these steps:
    1. Remove the PRUSA 3D printer drivers in control panel, under printers & devices. Apart from Slic3r PE and PrusaControl. This way you will not lose any of your saved profiles.
    2. Remove all remaining PRUSA related software in control panel, under Programs and functions.
    3. Turn off the printer and rebooted PC.
    4. Check if you really have the latest drivers at Prusa3D drivers.
    5. Turn on the printer and follow Firmware upgrade and flashing.
  5. LCD shows only squares after firmware update - If the LCD and menu was working correctly before the firmware update, firmware for different printer model was flashed. Make sure that you did select proper one (MK2/ MK3/ Multimaterial).
  6. For MAC owners only. If you happen to just download the FirmwareUpdater and whatever you do, it does not work. Try a simple reboot your MAC and do the whole process again. 

None of the problems is permanent 

Our bootloader is "read-only". That means that even if you upload improper firmware or make any other mistake. There is always a way how to make things right. The best practice when uploading or flashing simply does not work is to follow steps for Factory reset of all data

Would have any problems with Firmware updating or flashing. Do not hesitate to contact us at

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