English
Login

USB not detected

(MINI/MINI+)

Relevant for

MINI
MINI+
6 comments
Article is also available in following languages
English
Čeština
Polski
Deutsch
Français
Español
Italiano
日本語

The Original Prusa MINI uses USB flash storage to read G-codes during printing. It can happen that the USB drive is not recognized when inserted and the display will say "No USB", even when a USB is inserted. Since this issue can have several different causes and culprits, there is unfortunately not one universal way to fix it. Here we will go through some of the steps to do and things to check to resolve this.

How it can appear

  • USB drive is not recognized at all.
  • USB drive is not recognized when inserted but becomes visible after restarting the printer.
  • USB drive is functional for printing, but firmware updating does not work.
If the printer will detect the USB drive and can begin a print, but with eventual abnormal behavior it can indicate a faulty USB drive. However, it is more likely the G-code itself is corrupted. Try to export and copy the G-code to the USB drive again.

Flash the firmware

If the USB drive is not recognized when inserted but becomes visible after restarting the printer, it is most likely a firmware issue. Handling of USB storage media is improved with each update.

If the USB stick only works for printing, but not for Flashing the firmware, please attempt the steps outlined below in this article, but you may need to use a different USB drive.

Check the files and folder

Filenames

Some languages have special characters or diacritics that cause issues when attempting to read the drive. This has also caused the Watchdog error when attempting to print. Therefore, make sure you only use standard Latin letters in upper and lower-case. This is also why you will find that PrusaSlicer will autogenerate filenames with an underscore (_) instead of spaces. It is not always necessary, but to ensure backward and future compatibility, we recommend following these guidelines.

Filenames do not have a set maximum length of characters. However, they may not display correctly if they are very long. Therefore, make sure you do not make filenames unnecessarily long.

Folder structure

The same restrictions apply to the type and length of characters in folder names. Moreover, it is also good to know that a folder tree can only be 10 folders deep, i.e USB/Folder1/Folder2/Folder3/Folder4/Folder4/Folder6/Folder7/Folder8/Folder9/Folder10/

File types

The printer will ignore files that it can not read. However, since the printer's firmware is updated using the USB drive, it can happen that you will have multiple firmware files on the drive at any given time. This can cause conflicts, so make sure you delete these and try to only have them present for the flashing process, then delete them.

Corrupted USB drive

The easiest way to test this theory is to try with another (preferably new) USB drive, formatted to FAT32. ExFAT is not compatible. However, there are some procedures you can try with your current USB drive.

Repair the filesystem (keeps files)

The filesystem can become corrupted when you pull out the stick without unmounting/ejecting it. Most OSs have built-in features for "Recovery" or "Repair". There is also a range of third-party software with this functionality. However, the procedure brings few benefits, besides keeping your files and formatting, compared to if you reformat the drive. It is also a slower process.

Reformat to FAT32 (removes all data)

This will clear all the files on the disk and build the filesystem anew. Only FAT32 is supported! For drives over 32 GB, you will need a 3rd party application. For more information on formatting USB drives and SD cards, please see SD cards and USB drives.

 

4 comments

Log in  to post a comment
Ryan Merrell
For what it's worth, I was on 4.3.1 and was experiencing this issue. Switching to 2048 bytes for Allocation size did nothing for me. I tried multiple devices, ensured they were all FAT32 using Rufus. Nothing. Finally, it wasn't until I tried a SanDisk 64 GB stick, formated to Large FAT with 32k allocation size did it finally work. I've seen some others post about only getting it to work with SanDisk. So I don't know what actually fixed it, but man this was a frustrating experience!  But I'm now on the latest firmware, so all is well that ends well I guess.
Chris Barnes
I ran into this problem as well.  If anyone is still attempting to upgrade I used a few extra steps in order to get mine to work.  For each step I had to reformat the drive with "Allocated Unit Size" 2048 bytes. First I downgraded to 4.3.0 with freshly formatted 1GB USB drive.  "prusa3d_fw_4_3_0_MINI.bbf" Next I upgraded to 4.4.0 with the same now re-formatted drive.  This drive had the bootloader and the new firmware files on it.  "mini_release_boot_4.4.0+4180.bbf" and "mini_release_boot_update_pre_4.4_4.4.0+4180.bbf". This step took some time to upgrade the bootloader and then on self restart failed to load the new firmware.  I tried several time with no luck.  I realized I should try to reformat the drive again and place the same two files on it. It worked with the new bootloader and the new 4.4.0 firmware.
Paul
Chris, my mini is only 4.2.1, I've even removed the old female usb for a new one, stil "no usb", any tips?
BeckTuning
I had a similar issue the thumb drive would show as inserted but when you clicked on it the screen would show no files on the drive even when it was formated in FAT32. If you format the drive with a master boot record the drive will work again with the mini.
Gordon
Note that another option might be that the actual port itself might be broken.  In my case, the little bit of plastic inside had broken off.  Don't know about you, but I've never experienced that with any USB port, ever.
Prusa told me it wasn't covered by the warranty because of their 'normal usage' clause (!), i.e. it was expected wear and tear.  It certainly beggars my belief.
Going forwards, when I've replaced the mainboard to get a working USB port again, I'll make sure I just use a USB extension cable to minimise the 'wear and tear' on what is presumably a low quality part on that board.
Paul
Gordon, I've just bought a second hand mini, it has the no usb and also the female on the circuit board was in bits. So my question is, before I waste even more money on this, did the buddy board replacement cure the "no usb" fault