MIDI UART USB converter

Bi-directional converter between MIDI USB and MIDI UART. There are many pages that describe how to connect a UART port to DIN connectors so it is not covered here.

Maximum System Exclusive size is 1024 bytes. This can be bigger on SAMD boards which have more RAM.

Install MIDI Library (version 4.3.1) and MIDIUSB libraries using the Arduino IDE library manager. MIDI Library version 5 and newer do not work with large SysEx.

Tested in 32u4 boards such as Arduino Leonardo, SparkFun Pro Micro, and Adafuit Itsy Bitsy 32u4.

Tested on Arduino Zero, Adafruit Trinket M0, and Adafruit QT Py. It might work on other SAMD21 boards. Either Arduino or TinyUSB stack can be used.

Tested on Raspberry Pi Pico using the TinyUSB stack and the Earle Philhower Arduino Core for RP2040. It might work on other RP2040 boards.

Testing

Tested in with hardware loop back on UART Tx/Rx using SendMIDI and ReceiveMIDI.

In one command line window run receivemidi like this:

$ receivemidi dev arduino

In another command line window run sendmidi with the test script receivemidi.txt like this:

$ sendmidi dev arduino file receivemidi.txt

Compare the output of receivemidi (redirect output to a file) with the receivemidi.txt test script.

Hardware

All of the following run MIDIUARTUSB.

Arduino Leonardo (32u4) with SparkFun MIDI shield. The buttons and pots are not used in this program.

Pro Micro (32u4) 5V with MIDI breakout board.

Adafruit Trinket M0 (SAMD21) 3.3V with MIDI breakout board. Note the different resistor values on the MIDI board for 3.3V operation.

Options

Ground pin 2 to enable MIDI pass thru.

Trinket M0 firmware

Compiled programs can be burned into the Trinket M0 just by dragging and dropping a UF2 file on to the Trinket M0 USB drive. There is no need to install the Arduino IDE, source code, or USB serial device driver.

• Download the UF2 file.
• Plug in the Trinket M0 to the computer.
• Double tap the Trinket M0 reset button.
• When the TRINKETBOOT USB drive appears, drop the UF2 file on to the drive.
• Wait until the Trinket M0 reboots.

References

https://www.midi.org/specifications/

http://www.usb.org/developers/docs/devclass_docs/midi10.pdf

https://github.com/gbevin/ReceiveMIDI

https://github.com/gbevin/SendMIDI