A system that translates MIDI-messages to 1V/octave analogue control voltages from 0-5V.MIDI is recieved from the MIDI-connector, and is isolated from the cicruit with an optocoupler.The MIDI messages are received by the PIC MCU using it's built in UART support. The MCU only interprets MIDI messages "Note on", "Note off" and "Pitch Bend" and it's according value.
The output control voltages are generated by a 12-bit DAC. The MCU sends the appropiate levelsto the DAC using I2C. The pitch bend bends a note up to 2 semitones up or down.
There is also one gate output that goes high (5V) when a tone is on, and one trigger that outputs a 5V spike when a MIDI-message is recieved (both "Note on" and "Note off").
The system uses a low note priority, since it can only output one voltage level at a time. A 5V reference is used to drive the DAC.
A linear regulator is driven by the 9V input to 5V for the system. The regulator makes it possible to run this board from other voltages than 9V, but the current limiting resistor in series with the 5V reference may need to be resized.