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Church Of The
Swimming Elephant



The interface operates at 31.25 (+/- 1%) Kbaud, asynchronous, with a start bit, 8 data bits (D0 to D7), and a stop bit. This makes a total of 10 bits for a period of 320 microseconds per serial byte.

Circuit: 5 mA current loop type. Logical 0 is current ON. One output shall drive one and only one input. The receiver shall be opto-isolated and require less than 5 mA to turn on. Sharp PC-900 and HP 6N138 optoisolators have been found acceptable. Other high-speed optoisolators may be satisfactory. Rise and fall times should be less than 2 microseconds.

Connectors: DIN 5 pin (180 degree) female panel mount receptacle. An example is the SWITCHCRAFT 57 GB5F. The connectors shall be labelled "MIDI IN" and "MIDI OUT". Note that pins 1 and 3 are not used, and should be left unconnected in the receiver and transmitter.


  1. Optoisolator is Sharp PC-900. (HP 6N138 or other optoisolator can be used with appropriate changes.)
  2. Gates "A" are IC or transistor.
  3. Resistors are 5%
Cables shall have a maximum length of fifty feet (15 meters), and shall be terminated on each end by a corresponding 5-pin DIN male plug, such as the SWITCHCRAFT 05GM5M. The cable shall be shielded twisted pair, with the shield connected to pin 2 at both ends.

A "MIDI THRU" output may be provided if needed, which provides a direct copy of data coming in MIDI IN. For very long chain lengths (more than three instruments), higher-speed optoisolators must be used to avoid additive rise/fall time errors which affect pulse width duty cycle.

  • Introduction & Conventions
  • Hardware
  • Message Types
  • Data Types
  • Channel Modes
  • Summary of Status Bytes
  • Channel Voice Messages
  • System Common Messages
  • System Real Time Messages
  • System Exclusive Messages
  • Controllers




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    Service Details

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    Church of the Swimming Elephant©1999, 2000, 2001, 2002, 2003 is a wholly owned subsidiary of Packetderm, LLC.

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    210 Park Ave #308
    Worcester, MA 01609