Firmware updating & flashing problems

Updated 3 months ago ​by Tomáš Chvalina

Always check to confirm that the latest driver package is installed before flashing the newest firmware. This can be done on the Prusa3D drivers page. Before completing the 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. 
PrusaSlicer will detect the USB-connected printer even when it is powered off, but in order to upgrade the firmware, the printer has to be powered on!

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 Firmware Updater tool in PrusaSlicer confirms that the process was successfully completed.
  2. Timeout error - the Firmware Updater tool is not getting a response from the miniRAMBo or EINSY RAMBo board. Check that your printer is powered on. The 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 the firmware and select the .hex file for your printer model.
  4. The printer is showing up in Device manager, but not among COM devices - If you can find the printer in the device manager, but not as a COM device, follow these steps:
    1. Reinstall the drivers from the installation folder: C:\Program Files\Prusa3D\Rambo\dpinstx64.exe (64 bit systems) or C:\Program Files\Prusa3D\Rambo\dpinstx86.exe (32 bit systems)
    2. Restart your PC after you do so.
    3. Check if the printer is showing up in device manager as a COM device. Use that COM port and manually fill it in the port section in the software.
  5. Avrdude.exe - the  Firmware Updater tool was not able to find the proper COM port. In order to solve this problem. Follow these steps:
    1. Remove the PRUSA 3D printer drivers in the control panel, under printers & devices, including PrusaSlicer and other apps. You will not lose any of your saved profiles.
    2. Remove all remaining PRUSA related software in the control panel, under Programs and functions.
    3. Turn off the printer and reboot the PC.
    4. Check to confirm you really have the latest drivers at Prusa3D drivers.
    5. Turn on the printer and follow Firmware upgrade and flashing.
  6. LCD shows only squares after firmware update - If the LCD and menu were working correctly before the firmware update, then firmware for different a printer model was flashed. Make sure you selected the proper one (MK2/ MK3/ Multimaterial).

None of the problems are 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 to make things right. The best practice when uploading or flashing simply does not work is to follow the steps for a Factory reset of all data.


Find out more troubleshooting tips here: Community Forum | Assembly Manuals | Youtube channel |

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