iTWOc, midi to i2c adapter

I have made a few multipurpose boards, that could work as simple midi to i2c adapter if anyone feels interested.

It features din midi in, trough 3.5mm connector (and out) 2 i2c ports trough 3.5mm connectors, an encoder and a display, i might just populate midi in an i2c connector for this purpose.

I have not populated them yet, but the design is from another board ive made that works.

I have a few to sell once populated and tested, that said i’m no expert in electronics or programming,
so this is a solution for those feeling desperate as i once did. Otherwise i suggest you wait for transit:
more info to come…
Aiming at around 50eu or lower

My prototype firmware sends two four voice poly channels that rotates trough the free voices prioritizing the first channel that was freed. To not cut off the decay/release envelopes. Then a lot of mono channels and cc’s(can’t remember how many, but it makes use of the 100 i2c channels of the 301)
Todo: add midi clock and start stop messages


Yup for sure, I’d be interested, all the other upcoming “solutions” are delayed or whatever so let’s make this pretty simple module happen!! :slight_smile:

I notice the usb port, would this have usb midi host capability? Also what microcontroller are you using? I have been working on my own modular electronics projects and have been thinking of wading into the ER-301 i2c stuff as well.

It’s using a samd21, like the arduino zero. I’m not certain about the USB host. I need to test before I can confirm. It should have host compability, but the arduino lib have some varnings about not being completely finished or compatible with everything. I just put connector on the pcb hoping it will work

1 Like

I would be really interested in a €50 module that would let me use lots of MIDI cc’s from my sequencer into the ER-301. If you need pre-orders to complete the project, I’m in !

This looks to give us a couple of addressable i2c lines, midi 8cv outs(!) and an online editor??

1 Like

Call me desperate. I’m definitely in. This will work great until Transit is here. Thanks for doing this!

1 Like

in the meantime i would be glad if anyone would fill out my market research, about a new midi,cv,osc etc interface

1 Like

im a bit busy atm so i have not had time to start assamble yet :frowning:

I have successfully assembled one of the boards, it was a bit of a pain hehe…

But it works! midi in and out are working, the i2c ports works. And im trying to get the usb host to work, but no luck so far…

Successfully sent USB midi and converted it to i2c that the 301 happily accepted!


After some more tests with usb host i think i will abandon that for now, don’t have the time to dive into this atm.

I just need to implement din midi in my script and its good to go.

Hers is an example of using ableton to sequence 301 as a midi device

Using 3 mono voices for percussion, and one 4 voice poly voice for the chords


How are you distributing the different midi data (note on, off, ccs, etc) to i2c? like if I have midi cc messages coming on channel 3 cc 40 how do I specify that in the 301?

as of now they are fixed, im not at my computer, but something like cc1-20 on midi channel 1 is set to be sent to i2c channels 80-100

while polyfonic note data is sent to port 1-10
monovoices are i2c port 10-20
and so on. im gonna make it easy to change these assignments in the future.

gonna make a better documenteation of the current setup soon

(and sorry i havent aswered your pm, no tiiiime! gonna try tommorow)

1 Like

That makes sense. Also no sweat on responding, I know how things are. I have been spending time getting a module working and yesterday I finally got my new pcb’s and got a prototype that actually works. Now I get to sit down and clean up my test program.

It’s great. Have you thought about releasing this project as open source?

Nice work! Any chance mpe could get added as well? I dream of one day using my Sensel Morph controller with my er301 over usb to build pseudo Buchla 700 patches. I have a Shuttle Control, but it is limited to only 16 outputs and the er301’s 12 inputs. I’ve also had issues in the past with dropped notes and latency on the er301 when trying to process that many voltages coming from Shuttle Control.

Hi there, how exactly does the MIDI>i2c implementation work?

I’m interested in perhaps ordering this seeing as all other projects are basically dead

Actually i have paused this for a bit, mostly beacuse have other larger more important projects to work on, and also have some minor errors on the pcb. im happy to sell the pcb for cheap and provide my code as is, but thats all i got time for atm.
just remember there is alot a super small smd and a optional mod for midi out(makes it a bit more reliable)

Sorry for teasing this prematurely everyone!

Then no rush. I was wondering though how it works in practice?

well, its quite simple, i just read the midi bytes, multiply them to get the corresponding i2c data, and send that out via i2c, i2c is one of the more common ways of communicate between a micro controller and its peripherals on a pcb (sensors etc). so its very well documented and easy to use. This is a very simplified explanation. sry if this was oblivious to you!