Starting ttymidi in verbose mode :

ttymidi -s /dev/ttyAMA0 -b 38400 -v

This version adds MIDI one bytes Beatclock commands (Clock, start, stop, continue) Needs a complete refactoring but seems to work.

ttyMIDI is a GPL-licensed program that allows external serial devices to interface with the ALSA sequencer.

Authors: Thiago Teixeira (Original developer and maintainer) + Jari Suominen http://www.varal.org/ttymidi/

The ttyMIDI source code is comprised of a single C file. To compile it, just run the following command:

make

This program depends on libasound2, so you should have the development headers for that installed. In Debian or Ubuntu, you can install it by running:

sudo apt-get install libasound2-dev

After you compile ttyMIDI, you may wish to copy it to /usr/bin for easy access. This can be done simply by following command:

sudo make install

ttyMIDI creates an ALSA MIDI output port that can be interfaced to any compatible program. This is done in the following manner:

ttymidi -s /dev/ttyUSB0 &         # start ttyMIDI
timidity -iA &                    # start some ALSA compatible MIDI program
aconnect -i                       # list available MIDI input clients
aconnect -o                       # list available MIDI output clients
aconnect 128:0 129:0              # where 128 and 129 are the client numbers for
                                  # ttyMIDI and timidity

Further, ttyMIDI creates an ALSA MIDI input port that feeds incoming MIDI events back to the serial port. Before better documentation exists, check the header file of the ardumidi library to figure out how to read this data at the Arduino end.

If you would like to use a GUI to connect your MIDI clients, there are many available. One of my favorites is qjackctl.

TTYMIDI SPECIFICATION

The message format expected by ttyMIDI is based on what I could gather about the MIDI specification online. I tried to make it as similar as possible to the specification, but some differences exist. The good news is that as long as you follow the specification described below, everything should work.

Every MIDI command is sent through the serial port as 3 bytes. The first byte contains the command type and channel. After that, 2 parameter bytes are transmitted. To simplify the decoding process, ttyMIDI does not support "running status", and it also forces every command into 3 bytes. So even commands which only have 1 parameter must transmit byte #3 (transmitting a 0 in this case). This is described in more details in the table below:

byte1 byte2 byte3 Command name

0x80-0x8F Key # (0-127) Off Velocity (0-127) Note OFF 0x90-0x90 Key # (0-127) On Velocity (0-127) Note ON 0xA0-0xA0 Key # (0-127) Pressure (0-127) Poly Key Pressure 0xB0-0xB0 Control # (0-127) Control Value (0-127) Control Change 0xC0-0xC0 Program # (0-127) Not Used (send 0) Program Change 0xD0-0xD0 Pressure Value (0-127) Not Used (send 0) Mono Key Pressure (Channel Pressure) 0xE0-0xE0 Range LSB (0-127) Range MSB (0-127) Pitch Bend

Not implemented: 0xF0-0xF0 Manufacturer's ID Model ID System

Byte #1 is given as COMMAND + CHANNEL. So, for example, 0xE3 is the Pitch Bend command (0xE0) for channel 4 (0x03).