In order to make it simple to get up and running with your Trellis M4 Expressive MIDI Controller with no programming required, we've created a drag-and-drop firmware you can use. You can skip to the page Custom Code in Arduino if you want to customize things!

If you're just getting started with your Trellis M4, there is lots more info here in the main Learn Guide!


First, download the firmware file linked in the button below and save it to your computer hard drive somewhere you'll be able to find it, such as your Downloads folder.

This program will replace CircuitPython, to get back to your CircuitPython projects, reinstall it by following

Install the Firmware

Plug your Trellis M4 into your computer with a good quality, data capable USB cable. Life is too short to go through the pain of accidentally using a power-only USB cable, so please round up any you own, cut them in half, travel to a distant land, bury them, and dance on their grave.

Your Trellis M4 will start up, and you'll see a purple indicator light on the back side.

Bootloader Mode

Now, we'll put the Trellis M4 into "bootloader" mode. In this mode it will appear as a USB drive on your computer and will be ready to receive a new .uf2 firmware file. Use a thin, pointed object such as a headphone plug to double-click the reset button on the back side of the board.

Once you have double-clicked the reset button, the indicator LED will turn green. You'll notice a new USB drive appear on your computer named TRELM4BOOT, this is the bootloader USB storage built right into the Trellis M4. It is now ready to receive the firmware file.

Drag and Drop

Now, drag the TM4MIDIC.UF2 file onto the TRELM4BOOT drive. The file will copy over in a few seconds and then the Trellis M4 will automatically restart itself (you'll see the TRELM4BOOT drive dissapear, don't worry, this is normal!). The status LED will return to purple, indicating regular operation mode.

Congratulations, you've updated the firmware and you're ready to play!

If you ever need to manually switch out of bootloader mode, simply press the reset button one time.

Test MIDI Output

You can test to see that your Trellis M4 is outputting MIDI signals properly by using a MIDI utility. These will report all activity coming from any MIDI controller plugged into your system. Here are some to try:

This guide was first published on Nov 11, 2018. It was last updated on Nov 11, 2018.

This page (Firmware Upload) was last updated on Nov 09, 2018.

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