The Technology of MIDI
- MIDI Messages
- MIDI Transports
- Standard MIDI Files
Part Two: MIDI Transports
Many different transports can be used for MIDI messages. The speed of the transport determines how much MIDI data can be carried, and how quickly it will be received.
MIDI-DIN
The MIDI DIN (or "5-Pin MIDI") transport (Figure 1, below) was considered adequate when it was developed as the standard for MIDI way back in 1983. It is relatively slow compared to other common transports available today, but you will find this same connector on most MIDI-equipped devices because it is still more than adequate for communication on one device. For systems with multiple devices (such as where a computer is used), other transports are often used.
Serial, Parallel, and Joystick Ports
Before USB and FireWire, personal computers were generally equipped with serial, parallel, and (possibly) joystick ports, all of which have been used for connecting MIDI-equipped instruments (through special adapters). Though not always faster than MIDI-DIN, these connectors were already available on computers and that made them an economical alternative. Unfortunately, many Joystick MIDI Adapters don't meet the electrical standards for MIDI, as defined by the MMA. (A diagram of the proper design for a joystick to MIDI adapter can viewed here, along with with an explanation of the problems that can occur).
High Speed Serial Ports (such as those available on early Macintosh computers) support communication speeds roughly 20 times faster than MIDI-DIN, making it possible for companies to develop and market "multiport" MIDI interfaces that connect multiple MIDI-DINs to the computer. In this manner it is possible to have the computer address many different MIDI-equipped devices at the same time.
USB and FireWire
More recent computers are all equipped with USB and/or FireWire connectors, and these are now most often used for connecting MIDI devices to computers. The MMA has approved a standard for MIDI over IEEE-1394 (FireWire), which is available for download on this site. The MMA has not approved any specific standard for MIDI over USB, and so there are a number of different proprietary (manufacturer-specific) ways to send MIDI over USB, as well as a specification developed by the USB Implementors Forum (USB-IF).
Ethernet & Internet
Because of the Internet, in recent years there has been a significant increase in the use of Ethernet as a networking technology. Most business and many homes are now equipped with Cat-5 (wired) Ethernet networks, and the popular wireless technologies (802.11b/g) are versions of the same technology. Ethernet operates at speeds of 10 million to 1000 million bits per second, compared to MIDI Din at only 32 thousand bits. With so much speed, and so many people connected via Ethernet and the Internet, its no wonder many people dream about "MIDI-Over-Ethernet". For the current story on current products and standardization efforts around Ethernet (and similar networking technologies), click here.