little-scale: USB MIDI to Eight Gates and Sixteen CV Outs

Note: A newer version of this project can be found here: https://little-scale.blogspot.com/2019/01/12-gate-16-cv-usb-midi-interface-bom.html

It is highly recommended to build the newer version linked to above.

This is a simple USB MIDI to eight gates and sixteen control voltage outputs. The gates are 0V for off and 5V for on. The control voltage outputs are 12-bit and 0V to 4.096V in range, with a four octave range for pitch. The gate outputs are via 1k resistors. The cv outputs are via 100 ohm resistors.

A MIDI control change message on channel 16 changes the mapping mode of the interface. Channel 16, control 110 and value 64 or above sets the mode to mode 0. Channel 16, control 111 and value 64 or above sets the mode to mode 1. Channel 16, control 112 and value 64 or above sets the mode to mode 2.

In mapping mode 0, gates 1 to 8 respond to note on and note off messages on MIDI channels 1 to 8. CV outputs 1 to 8 are determined by the pitch of note on messages on MIDI channels 1 to 8. CV outputs 9 to 16 are determined by the velocity of note on messages on MIDI channels 1 to 8.

In mapping mode 1, gates 1 to 8 respond to note on and note off messages on MIDI channels 1 to 8. CV outputs 1 to 8 are determined by the pitch of note on messages on MIDI channels 1 to 8. CV outputs 9 to 16 are determined by the control change message for controller 1 on MIDI channels 1 to 8.

In mapping mode 2, gates 1 to 8 respond to note on and note off messages on MIDI channels 1 to 8. CV outputs 1 to 16 are determined by the pitch bend value of pitch bend messages on MIDI channels 1 to 16.