Troubleshooting downloads with WebUSB

Having issues pairing your Calliope mini with WebUSB? Let’s try to figure out why!

Step 1: Check your cable

Make sure that your Calliope mini is connected to your computer with a micro USB cable. For example, in Windows Explorer you should see a MINI drive appear when it’s connected.

MINI drive

If you can see the MINI drive go to step 2.

If you can’t see the drive:

  • Make sure that the USB cable is working.

    Does the cable work on another computer? If not, find a different cable to use. Some cables may only provide a power connection and don’t actually transfer data.

  • Try another USB port on your computer.

Is the cable good but you still can’t see the MINI drive? Hmm, you might have a problem with your Calliope mini. Try the additional steps described in the faq page at calliope.cc.

Step 2: Check your firmware version

If your downloads still aren’t working, it’s possible that the firmware version on the Calliope mini needs an update. Let’s check:

1. Go to the MINI drive

Navigate to the MINI drive in the computer’s File Explorer.

2. Open the DETAILS.TXT file

Look for the DETAILS.TXT file and open it.

3. Find the firmware version number

Look for a line in the file that says the version number. It should say Version:

Firmware version number in DETAILS.TXT

or Interface Version:

Interface version number in DETAILS.TXT

If the version is 0234, 0241, 0243 you NEED to update the firmware on your Calliope mini. Go to Step 3 and follow the upgrade instructions.

If the version is 0249, 0250 or higher, you have the right firmware go to step 4.

Step 3: Upgrade the firmware

1. Put your Calliope mini into MAINTENANCE Mode

To do this, unplug the USB cable from the Calliope mini and then reconnect the USB cable while you hold down the reset button. Once you insert the cable, you can release the reset button. You should now see a MAINTENANCE drive instead of the MINI drive like before. Also, a yellow LED light will stay on next to the reset button.

MAINTENANCE gesture

2. Download the firmware file

Download the firmware .hex file.

3. Transfer to the MAINTENANCE drive

Drag and drop that file onto the MAINTENANCE drive.

4. Look for the flashing LED

The yellow LED will flash while the HEX file is copying. When the copy finishes, the LED will go off and the Calliope mini resets. The MAINTENANCE drive now changes back to MINI.

5. Upgrade complete

The upgrade is complete! You can open the DETAILS.TXT file to check and see that the firmware version changed to the match the version of the HEX file you copied.

Firmware guide

If you want to know more about connecting the board, MAINTENANCE Mode, and upgrading the firmware, read about it in the Firmware guide.

Step 4: Check your browser version

WebUSB is a fairly new feature and may require you to update your browser. Check that your browser version matches one of those in the table below.

Browser versions for Android, Chrome OS, Linux, macOS, and Windows 10, 11:

Browser Version
Chrome 61+
Edge 79+
Safari Not supported


For other browsers, see the supported versions in the Can I use? table for WebUSB.

Step 5: Pair device

Once you’ve updated the firmware, open the Chrome Browser, go to the editor and click on Pair Device in the gearwheel menu. See WebUSB for pairing instructions.

Enjoy fast downloads!