MIDI to CV and Velocity

MIDI to CV/Gate - 1 volt per octave

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ATMega 328 based MIDI to CV converter.
Outputs 1 volt per octave from 0 to 7 volts, 0 volts being A0 (27.5Hz)
Calibrated for the MFOS VCO

This has 2 operating modes and a test mode, that just displays the MIDI note number on the screen.

Mode 1 - Single channel CV/Velocity- This outputs 1 volt per octave and velocity with a gate output. It allows for 'rollover' so if the next key is pressed, the gate stays on but the voltage output changes, release the new key the gate goes off and the previous key does nothing.

Mode 2 - Dual channel CV/Velocity - This outputs 2 channels, there's a 2 byte array that the note is stored in once pressed, if a second key is pressed it goes to the next slot, triggering a second gate and second CV output - useful for a dual oscillaltor synth.

The MIDI note is calculated into a DAC value by the microcontroller, and goes to an MCP4922 SPI dual DAC, 12 bit resolution so more  range than trying to filter PWM, which would be 8 bit

8 bit 0 to 255, 12 bit 0 to 4096.. big difference.

At this point we only have 0 to 5 volts, so an op-amp amplifies it by 1.62 giving a 0-7 volt output, I use a TL084, with one being an amp and one a voltage follower to buffer the output.



Adobe Portable Document Format - 64.49 kB - 07/08/2018 at 15:48


  • PCB

    RH Electronics07/08/2018 at 15:51 0 comments

    I've ordered a PCB, I will have some spares so if anyone is interested in this project, I can arrange a PCB and pre programmed chip.

    It's programmed using the Arduino IDE but I've coded not using any libraries or arduino functions

  • Updated Schematic

    RH Electronics07/08/2018 at 15:50 0 comments

    Full circuit diagram available in the files section

    The circuit uses
    1x 74HC595
    2x MCP4922 12 bit DAC
    1x TL084 Op-Amp
    1x TL082 Op-Amp
    1x 6N138 opto isolator

    Programmed ATMega 328

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RH Electronics wrote 07/06/2018 at 10:10 point

My module will be 170x100 but it can be made any size you want.
I've designed a PCB which is 135x65, I will have some spares as the minimum order is 5

  Are you sure? yes | no

Richard Hogben wrote 07/05/2018 at 21:39 point

What size module will this be?

  Are you sure? yes | no

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