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midi2piousbhost Arduino Sketch

Hardware

This project uses the RP2040's USB hardware as a USB device to connect to the Arduino system, It uses the RP2040's PIO0 module to make a USB Host port. It uses the RP2040's UART1 for the serial MIDI port. Debug prints appear on the Arduino Serial device. This software will run on the Adafruit RP2040 Feather with USB Type A Host wired to the Adafruit MIDI Featherwing board.

Wire the 3.3V and Ground from the Feather board to the Featherwing Board. Wire the Featherwing Tx pin to pin D4 of the Feather board. Wire the Featherwing Rx pin to pin D5 of the Feather board. Connect the USB C port to the Arduino PC and the USB A port to your USB MIDI device. Wire MIDI IN and MIDI OUT to your Serial Port MIDI device.

You do not have to use these two boards to run this sketch. You can wire something up yourself for less money. Have a look at the pico-usb-midi-filter and pico-pio-midi-processor projects for some ideas. The Adafruit set is very convenient, however.

License Notes

Code that I have written is released under the MIT License. Some libraries the Arduino Sketch links to are released under other licenses. The discussion here may be helpful.

Software Build and Run

Make sure your Arduino IDE is set up to build software for RP2040 boards. If you have never used Arduino to build software for the RP2040 chip, you can find a good tutorial here. You should make sure your Board Manager has installed verion 3.6.3 or later of the Earle Philhower Arduino Core.

Once you are able to build and run a simple blink example, please use the Arduino IDE Library Manager to install the usb_midi_host library and all of its dependencies, plus the Pico-PIO-USB library and all of its dependencies.

Use a web browser to navigate to the midi2usbhost project page. Click the <> Code Button and select Download ZIP. The browser will download the file midi2usbhost-main.zip. Extract the ZIP file and copy the directory midi2usbhost/arduino/midi2piousbhost to your Sketch directory.

In the Arduino IDE, use File->Open... to load the midi2piousbhost/midi2piousbhost.ino file.

In the IDE Tools menu, set up the IDE as follows:

Tools->CPU Speed->120 MHz (or 240 MHz (Overclock))
Tools->USB Stack->"Adafruit TinyUSB"
Tools->Debug Port->Serial
Tools->Optimize: You can choose any option except Small (-Os) (Standard). I generally use Optimize Even More (-O3)

First time program load

Press and hold the Feather board's reset button. Press and hold the boot button. Release the reset button. Finally, release the Boot button. The board will mount like a USB flash drive. Once you have successfully downloaded a program to the board using the Arduino IDE, you won't have to go through this step again, even if you change or re-download the software to the board.

Running the code

Press the Upload icon in the Arduino IDE. The Sketch should compile and run. The Serial Monitor (115200 baud) should display

Core1 setup to run TinyUSB host with pio-usb            
MIDI To PIO USB Host

Plug a USB MIDI device to your target board through the adapter you have. The LED on the target board should illuminate to show the MIDI device has enumerated successfully. Also he Serial Monitor should display information about the MIDI device, and the serial MIDI to USB MIDI bridge should operate now for MIDI IN and MIDI OUT.

Always run a serial monitor

The sketch is written to make the board wait for a serial monitor program to connect to the board before anything else can happen. If that behavior does not work for you, look for lines similar to

  while (!Serial) {
    delay(100);   // wait for native usb
  }

and either comment them out or delete them.