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Thus, the 16 MIDI channels are mapped as follows:

SN76489 Chip 1, Channel 1: MIDI Channel 1 -36 semitones

SN76489 Chip 1, Channel 2: MIDI Channel 1 +24 semitones

SN76489 Chip 1, Channel 3: MIDI Channel 2 -36 semitones

SN76489 Chip 1, Channel 4: MIDI Channel 2 +24 semitones

SN76489 Chip 2, Channel 1: MIDI Channel 3 -36 semitones SN76489 Chip 2, Channel 2: MIDI Channel 3 +24 semitones SN76489 Chip 2, Channel 3: MIDI Channel 4 -36 semitones SN76489 Chip 2, Channel 4: MIDI Channel 4 +24 semitones

SN76489 Chip 3, Channel 1: MIDI Channel 5 -36 semitones SN76489 Chip 3, Channel 2: MIDI Channel 5 +24 semitones SN76489 Chip 3, Channel 3: MIDI Channel 6 -36 semitones SN76489 Chip 3, Channel 4: MIDI Channel 6 +24 semitones SN76489 Chip 4, Channel 1: MIDI Channel 7 -36 semitones SN76489 Chip 4, Channel 2: MIDI Channel 7 +24 semitones SN76489 Chip 4, Channel 3: MIDI Channel 8 -36 semitones SN76489 Chip 4, Channel 4: MIDI Channel 8 +24 semitones

SN76489 Chip 5, Channel 1: MIDI Channel 9 -36 semitones SN76489 Chip 5, Channel 2: MIDI Channel 9 +24 semitones SN76489 Chip 5, Channel 3: MIDI Channel 10 -36 semitones SN76489 Chip 5, Channel 4: MIDI Channel 10 +24 semitones SN76489 Chip 6, Channel 1: MIDI Channel 11 -36 semitones SN76489 Chip 6, Channel 2: MIDI Channel 11 +24 semitones SN76489 Chip 6, Channel 3: MIDI Channel 12 -36 semitones SN76489 Chip 6, Channel 4: MIDI Channel 12 +24 semitones SN76489 Chip 7, Channel 1: MIDI Channel 13 -36 semitones SN76489 Chip 7, Channel 2: MIDI Channel 13 +24 semitones SN76489 Chip 7, Channel 3: MIDI Channel 14 -36 semitones SN76489 Chip 7, Channel 4: MIDI Channel 14 +24 semitones SN76489 Chip 8, Channel 1: MIDI Channel 15 -36 semitones SN76489 Chip 8, Channel 2: MIDI Channel 15 +24 semitones SN76489 Chip 8, Channel 3: MIDI Channel 16 -36 semitones SN76489 Chip 8, Channel 4: MIDI Channel 16 +24 semitones



The hardware setup has one Teensy LC, with a common data bus (digital pins 0 - 7) and individual chip select (digital pins 8 - 15). One external 4 MHz crystal provides the timing for all eight SN76489.













Download the code here: http://milkcrate.com.au/_other/downloads/arduino/oct_sn76489.ino

The SN76489 is the same sound chip as found in the SEGA Master System. This is an array of eight SN76489 sound chips playable via USB MIDI, for a total of 32 hardware channels.