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

@nsm
Is it true that the Akso has four uarts? That would be super handy.

From my quick research (I am a layman with this kind of stuff) I found that the ARM CPU datasheet that is linked in the docs section indeed indicates some support for it but I don’t understand what it means in practice, are they usable through the IOs on the pcb?

4× USARTs/4x UARTs (ISO7816 interface,
LIN, IrDA, up to 12.5 Mbit/s) and 1x LPUART

The H7 processor actually has four UARTs and four USARTs as well as a low power UART. Off the top of my head I don’t remember how many can theoretically be used at the same time. The processor pins generally have many overlapping functions. In some cases particular pins are locked down as a single function in the Akso design (SDRAM IO for example). Any function available on a pin that has a physical test point on the board should be accessible with minor software tweaks.

See the first couple pages of the datasheet for a summary of the peripherals available.

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Thanks for the swift reply - I think this is a bit too challenging for me so I will put that task aside.

kind of related. i see the patcher (when creating a subpatch) still has the option for din input in the midi section. is that actually still routed to specific pins (so i can simply add the midi din part and be good, via a leftover midi board form axoloti for example) or is it just a leftover from the legacy patcher?

@lokki DIN input should be available with a simple breakout or Axoloti midi section. The pin assignment for MIDI DIN TX/RX is currently exactly the same as it is in Axoloti core. If you take a look at the diagram at the bottom of the reference section, notice pins VI down to G on the right side of the bottom view pinout. The intent is for those five pins to align with the five pin connector on the Axoloti MIDI board. VI is power in. Akso doesn’t use the signal in the AF position on the connector. G9 is MIDI RX. GE (PG14) is MIDI TX. G is ground.

I need to document this procedure in more clearly and put it up on the website.

Hey . Forgot to mention that I usually use both in axoloti . USB for 1 channel of controllers only , and the din out to spit out notes re tuned with pitch bend . And the din in for clock from the drum-machine

All this maddness just because of the original known issue with the usb hub :slight_smile: . It was working really great I must say .

Getting a breakout board now and will await the akso arrival to get started :metal:

can anyone recommend a compatible breakout board with more than 2 DIN sockets?

Are you looking for more inputs, or more outputs?

well, both.
for me, 2 ins and 2 outs would be optimal.
but even 1 in / 2 outs or 2 ins / 1 out would be better than regular 1 in / 1 out.

(USB —> MIDI adapters are not an option for me until USB hubs support in firmware, for the moment USB host port is assumed busy with something else.)

I haven’t seen any breakout with more than IN, OUT, THROUGH. Creating more OUT and THROUGH is simple, but adding inputs requires different programming by the MCU, since messages need to be merged.

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ok, i understand.
so, anything compatible with in / out / through or in / 2 outs?

For in/out, this should work:
https://www.amazon.com/ubld-it-MIDI-Breakout-Board-EZ/dp/B08JC1SZHG/ref=sr_1_1?dchild=1&keywords=midi+breakout&qid=1603901000&sr=8-1

In/out/through, but I don’t know if it needs modification to work on the 3.3v of Akso:
https://www.amazon.com/Musical-Breakout-Instrument-Interface-Compatible/dp/B07R8GQLSG/ref=pd_sbs_147_1/142-4489895-1671241?_encoding=UTF8&pd_rd_i=B07R8GQLSG&pd_rd_r=802159fa-a471-41f1-9613-d99cc4070d1f&pd_rd_w=YMPFt&pd_rd_wg=yJYQI&pf_rd_p=ff9b5089-1414-4e8f-9675-3397e98bf276&pf_rd_r=XJRTKV6V10RM4XVYFPQY&psc=1&refRID=XJRTKV6V10RM4XVYFPQY

Also, your description ‘2 ins, 2 outs’ or something like that, doesn’t fully describe what you actually want. Do you want the outputs to be duplicates, or separate MIDI streams?

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For something like this — can you just attach 3.5” trs jacks instead of the din sockets?

Also — could you attach both, knowing that means they would be duplicate signals? Honestly i would only use one or the other at a time but it would be handy to have the jack option for interfacing with other gear.

Yes, that will work. As you understand, you would use either DIN or TRS, but not both at once.

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thanks for recommendations!

separate streams.

What are you trying to do? Do you want to post your project in #workbench so we can see what you’re doing and maybe help figure out workarounds?

well… currently i’m in a situation of using one Axoloti per one machine in my rig for MIDI processing.

i’m trying to figure out is it possible to reduce the number of Axoloti, because they are underloaded, take extra space and need extra PSUs.

also, i love the form factor of Akso and thinking about making things more compact.

So you’re only using an Akso for MIDI distribution? It’s not doing anything with the signal?

I’ll continue this conversation over in #workbench because this doesn’t have to do with MIDI optocouplers.

@nsm I soldered connectors onto my akso and the breakout-board (the hobbytronics.co.uk one).

I connected G9 to rx and GE to tx but it does not seem to work. I think the solder-joints are ok.

There is an github issue about to midi transmission via USB not working and the related firmware code seems different to the axoloti one. So I wonder whether this also compromises the DIN IO.

I tried swapping the tx/rx wires without success.

After sending a dozen note-ons, the log shows “midi output overflow”.
Any help is appreciated, I am stuck. Has anyone else managed to get DIN midi working?

Hey @ivofx. Sorry to hear that you’re having trouble with this. Can you send me a link to the exact breakout board you’re using? I’ll just order it and try to replicate your setup exactly.

It may be that electrically everything is fine but that you have an issue at the software level. The MIDI routing functionality is slightly different in the current version of the Akso patcher. It includes changes that were developed for Axoloti but way after the last stable release. I would try digging around in the MIDI configuration dialogs to make sure that everything seems reasonable.