Goal: I have a few MIDI keyboards mouldering in the house and a newly built (by me) Erica/MKI modular synthesizer, but no way to get them to talk to one another. You could buy a gadget to do it, but where’s the fun in that? So let’s build a device which will generate output control voltages. The premise is to read in MIDI signals, use a RP2040 microcontroller to interpret the commands, and then use a D2A converter to output the relevant control voltages. Discussion of precedent, parts, and design goals…

Precedent/previous work

AxWax has a two-part series describing a build like this. In his first episode he generates a control voltage (CV) (and uses the direct output from a RP2040 GPIO pin as the trigger). In the second episode he expands this to generate two CV outputs and reads from some sensors. This is a good starting point for our project

Like me, he uses an RP2040 and has a python-based code posted online. It uses the SimpleMIDIDecoder.py library.

Areas where I want to do things differently: (i) use a pre-build MIDI interface (with the optocoupler already incorporated); (ii) use a Quad D2A rather than use a dual…because…why not! But otherwise, this is a solid starting point

Some areas to pursue for the future

Bill of materials

To be continued…

part 2: Building the gadget

Parerga and Paralipomena