This command line script establishes Serial to MIDI bridge. It will be useful with micro controller boards such as Arduino, ESP32, they only have UART-USB interface.

I made this since useful Hairless MIDI Serial bridge program stopped working with OS X Catalina.

It processes most of MIDI messages. It has only very low latency (probably less than 5ms) so far.

This script needs python-rtmidi, PySerial and Python 3.

1. Install Python 3
2. Install pip
3. pip install python-rtmidi
4. pip install pyserial
5. Download serialmidi.py

MAC OS X example
$ python3 serialmidi.py --serial_name=/dev/cu.SLAB_USBtoUART --midi_in_name="IAC Bus 1" --midi_out_name="IAC Bus 2"

WINDOWS example
$ python.exe .\serialmidi.py --serial_name=COM4 --midi_in_name="loopMIDI Port IN 0" --midi_out_name="loopMIDI Port OUT 2"

1. Run serialmidi.py -h to see this help.

$ python3 serialmidi.py -h
usage: serialmidi.py [-h] --serial_name SERIAL_NAME [--baud BAUD]
                     [--midi_in_name MIDI_IN_NAME]
                     [--midi_out_name MIDI_OUT_NAME] [--debug]

Serial MIDI bridge

optional arguments:
  -h, --help            show this help message and exit
  --serial_name SERIAL_NAME
                        Serial port name. Required
  --baud BAUD           baud rate. Default is 115200
  --midi_in_name MIDI_IN_NAME
  --midi_out_name MIDI_OUT_NAME
  --debug               Print incoming / outgoing MIDI signals

2. Figure out serial port name and baud rate. Baud rate default is 115200.
3. Run serialmidi.py --serial_name=[serial_port] --baud=[baud]. Make sure it doesn't say "Serial port opening error.".
4. The script prints recognized MIDI devices. Use one of listed name as argument of --midi_in_name and --midi_out_name. Here is an example on OS X.

INFO:root:IN : 'IAC Bus 1','IAC Bus 2'
INFO:root:OUT : 'IAC Bus 1','IAC Bus 2'

You may want to use MIDI loop bus such as IAC Bus for OS X, or loopMIDI for Windows. Also, you need to use different bus in order to avoid signal loop.

5. If it is not working, try --debug option. It will dump all incoming / outgoing MIDI messages. Or create an issue on the GitHub page.

• Tested with OS X Catalina with ESP32 board, and Windows10 with loopMIDI.

• It's made for my ESP32 based synthesizer, so I tested MIDI IN a lot, but MIDI OUT. MIDI OUT message processing might have some bugs. Please let me know if you find it.