Making Things Talk

344 MAKING THINGS TALK

Other Useful Protocols

There are many more useful protocols than have been covered. Here are a few that you

might run across, along with some notes on where to begin learning about them.

MIDI

The Musical Instrument Digital Interface (MIDI) protocol

is a protocol for real-time communication between digital

musical instruments. It’s the granddaddy of digital

synthesizer protocols. Most music synthesizers, sequenc-

ers, samplers, keyboards, and workstations on the market

today speak MIDI. If you plan to make music using hardware,

you’re going to run across it. It’s a serial protocol running

at 31,250 bps. There’s a standard MIDI connector called

a DIN5 connector that you’ll find on all MIDI gear. All the

connectors on the gear are female plugs, and the cables all

have male connectors on both ends. Figure A-1 shows the

MIDI connector and a simple MIDI output circuit from an

Arduino board. You can find hundreds of examples of how

to send and receive MIDI data online.

MIDI messages are divided into three or more bytes. The

first byte, a command byte, is always greater than 127

in value. Its value depends on the command. The bytes

that follow it are called status bytes. All status bytes

have values less than 128. This makes it possible to tell a

command byte from a status byte by the value alone.

There are a number of different MIDI commands. The

most basic, note on ...