Do I need an optocoupler when adding a MIDI DIN breakout?

To add DIN-Midi, do I need an optocoupler and additional resistors or do I connect the wires straight to the io pins?

Having traditional midi is crucial to me, I like that the connectors come with the original Axoloti.
Otherwise the Akso seems fantastic, thank you!

Second question, on the image next to the usb-c ports it looks like there are two buttons.
Can they be used arbitrarily with code or do they have fixed functionality?


Hi, @ivofx. I really appreciate your support.

An optocoupler is not included on board. The assumption is that it will be included on the DIN breakout just as it is on the original Axoloti Core’s MIDI breakout section (and similar breakouts). The pinout starting from the VI power in pin five pins down matches the five pin connector on the original MIDI breakout section. If there is enough demand, I can create a custom breakout that will fit even more exactly and possibly have other connectors. Another approach we can explore is supporting DIN adapters that connect via USB.

One of the tactile switches is connected to the processor’s dedicated BOOT0 pin and is used to enter DFU mode for firmware flashing. The other is connected to processor pin PA10 and can be used arbitrarily.

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Thanks for the quick reply.
Any way to have DIN Midi in would be appreciated.
I think I will order a unit anyway, I love the Axoloti with it’s patcher and having more RAM/CPU seems great.
It’s only that I do not use cv and would want to sync via midi clock while having a USB-midi controller connected.

I placed my order, looking forward to be working with it!

I think I will control it with a Novation Zero SL mk2 which actually does have DIN Midi and can forward it to USB so I might be just fine.

Hello there!

There are many MIDI breakout with octocoupler embed available on the market.

This one seem to be quiet easy to set up with the board.


That’s great, thank you @Pierre.
I was not aware, this could be useful for the raspberry pi as well

You are much welcome.

was wondering just how many midi din are possible on an axoloti and an akso mini.
also (do you know) has anyone made a midi looper sequencer with it?

i mean like recording the midi in real time, preferably unquantized

Mr Bien (Bien ou bien??? ^^) to make a midi sequencer, you just need 1 midi in and 1 midi out to record and play up to 16 midi tracks (midi chanel 1 = track 1| midi chanel 2 = track 2 | midi chanel 3 etc etc )

Concerning objects for that task you can have a look in the Axo library - > poly8ARecorder_1 and polymidiXL

Ok but i don’t want to have to have a separate device to control multiple hardware synths. So akso does in fact have 4 uart and possibly one more that would work.

so rather than have a midi hub (or crossing fingers on thru) it can just connect to different devices. also for another project it could recognize the midi from different devices and say light up ws2812 to give pitch feedback. (i call it Colorier and i hope we all adopt it ;))

Nice , I will be getting one of these too . I made a little dirty hack from @lusol idea with a PI to get multiple usb devices into the axo . Will try with akso once I get it and get some spare time :slight_smile: cant wait for it .

Let us see & know how well you get with this little cheap midi breakouts .

@DrKoma Proper hub support is absolutely possible technically and will get in eventually. I think we need more general driver support for the host port overall. Like accessing data on a USB flash drive for example. It might sound bizarre, but we could even get to the point of being able to use normal USB audio interfaces directly. I haven’t implemented any software for it, but just to stress test I’ve hooked up my normal Behringer U-Phoria interface to the host port and it powers up just fine. I suspect that a lot of people have multichannel audio interfaces lying around that might be cool to reuse for quick and easy audio and midi IO.

One idea that might be worth exploring as a temporary workaround: making a simple driver for a normal USB MIDI adapter. Something like this:


personally i would stay away from such adapters. they are known for all sorts of problems, dropped messages, no sysex support. but of course there are good usb-midi adapters, for example the roland um-1 family.

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Yeah, it isn’t an ideal solution. It would just be cool to have support for that style of device for quick experiments.

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usb to midi adaptor support would be HUGE

iConnectivity have released a usb-c one

Which is more important? MIDI IN, or OUT?

Equally important IMO

what is the intent of that question?

for myself midi input is much more important since i use the axoloti (and the akso at some point) as a synth engine. but there are many “midi” users on the axoloti forums at least, people that create sequencers, midi mergers etc. for them midi output will be crucial.
so really, if there is an add-on board with din connectors it should contain midi in and out in any case.

I was just curious. Personally, I want USB Host so my Keystep works.

I received three breakout boards from already so I am prepared :wink:

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