Liz Clark's MIDI Friends Turn an Adafruit QT Py RP2040 Into a USB to Serial MIDI Adapter

Designed to bring USB MIDI support to older dedicated MIDI devices, this compact build uses cheap components and some CircuitPython.

Liz Clark has penned a guide to turning an Adafruit QT Py RP2040, based on the Raspberry Pi dual-core microcontroller of the same name, into a USB to serial MIDI adapter — by building low-cost "MIDI Friend" add-ons.

"This concept was inspired by Sandy Macdonald on Twitter," Clark writes of the project. "It makes for a compact and simple solution for interfacing hardware MIDI devices with USB. The MIDI friend breakouts plug directly into a QT Py RP2040 with socket headers."

The project is designed to make it easy to connect to traditional MIDI devices from any PC with a USB port. MIDI signals are sent over USB to the QT Py RP2040, which runs a CircuitPython program designed to accept the signals then forward them on over serial UART — pushing them out to a real MIDI device that lacks its own USB port.

A bit of CircuitPython and a small "MIDI Friend" add-on turns a QT Py RP2040 into a compact USB MIDI adapter. (📹: Liz Clark/Adafruit)

The "MIDI Friend" boards act as the hardware interface between the QT Py RP2040 and the target MIDI device. Built on prototyping board, the compact piggyback add-ons sit on top of the compact QT Py RP2040 and provide a 3.5mm tip-ring-sleeve (TRS) jack — wired to TRS-A or TRS-B, depending on the needs of your particular MIDI device — or a more traditional DIN-5 jack, plus the necessary passives.

"You can use the QT Py RP2040 with any application that supports USB MIDI," Clark explains, "such as a USB MIDI host or a software DAW (digital audio workstation). Plug your selected MIDI friend breakout into the QT Py RP2040 before plugging in any cables. Then, connect the QT Py RP2040 using a USB-C cable."

The full guide, including source code, wiring diagrams, and soldering instructions, is now available on the Adafruit Learn portal.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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