Extra Midi IO with Axoloti Midi Part

[Blindsmyth]

He there, I want to get @Hugo's extra midi input IO with onboard hardware.

I use the boards genuine midi IO already for talking with another board, so I want to get use PA2 and PA3 together with Hugo'S script for talking with the outside/nonaxoloti world.

The output works, connecting PA2 to "Midi Out".

The same didn't work for PA3, conencting it to "Midi In"
I tried both sending midi from my soundcard (tested and working with volca sample) to the axoloti midi part and connecting axoloti's "midi out" as on the pic to PA3. No midi arriving though!

Sending Midi from PA2 to PA3 worked well. So what am I doing wrong here?

[Blindsmyth]

So I got it to work but only by tapping from Mi5 directly.

When I tap from after the optocopler I still get nothing. Is this ok? I receive Midi from my volca sample. Are there any risks avoiding the optocopler like this? More likely to have ground loops maybe?

Btw I cut the Midi in out and out lines as in the pic from the first post.

[Gavin]

Do no avoid the optocopler.
If you avoid it, and your midi source is coming from a different power source, you could and or will cause damage to midi receive. This is why the optocopler is their, so the 2 power sources remain separated.
Its possible if you are not receiving midi, is because you may have damaged the midi in within the Axo from avoiding the optocopler.

[lokki]

how did you cut the original midi in and out? maybe there is still something connected to the midi in before the optocoupler that prevents it from working with external input.

[Blindsmyth]

Thx for the replies guys!

If you avoid it, and your midi source is coming from a different power source, you could and or will cause damage to midi receive. This is why the optocopler is their, so the 2 power sources remain separated.
Its possible if you are not receiving midi, is because you may have damaged the midi in within the Axo from avoiding the optocopler.

Ok thanks for pointing this out. The midi part of axoloti is working perfectly fine. The point is I do avoid the optocopler already by going from "MIDI IN" to "MIDI OUT" as on the schematic in the first post and vice versa between 2 axoloti boards. Aparently more people on the board are doing it like this, but do you think this is dangerous as well?

Then since I don't use the midi io hardware part I want to use it together with pin PA2 and PA3 to get extra Midi IO.
While sending midi from PA2 via axoloti midi out works, midi in didn't, or it only worked when hooking pin MI5 to PA3 directly.

how did you cut the original midi in and out? maybe there is still something connected to the midi in before the optocoupler that prevents it from working with external input.

I made a cut where you would usually break the midi part so between "JP2" and "JP3"

[Gavin]

The way I understand it, optocouplers are always added to the midi in, this is because any midi out has to go to a midi in and therefore will be isolated from the sources at midi in. Think of it as a safety for your midi gear including the Axo. Its not an issue if its from the same source.

Using PA2 and PA3 for extra midi definately works as I have found this working myself, but I did find a bug in it, when you change patches when running the Axo in standalone mode, it appears the midi through PA2 and PA3 disconnects. This may not be an issue for you if you don't plan to change patches in standalone mode.

My recomendation is to either use midi splitters or wait for the midi support via SUB hub to be implamented. I guess there may be other options as well, but recom,end the opotocouplers are there for a reason and have been part of the Midi hardware for a long time for our own benifit. There are vmany websites etc, that give the relevant circuits if you want to do your own optocoupler circuit etc, so may be worth reading some of these.

[Blindsmyth]

The way I understand it, optocouplers are always added to the midi in, this is because any midi out has to go to a midi in and therefore will be isolated from the sources at midi in. Think of it as a safety for your midi gear including the Axo. Its not an issue if its from the same source.

As far as I know the gpios of microcontrollers in the 80s didnt have enough power to transmit the signal on it's own, which is why they added the vbus line and then propably the optocoppler to isolate receiver and transmitter from each other.
But today this is not an issue, so when connecting two axos, or and axoloti and a teensy and everthing is on the same voltage range it should fine to just go from rx to tx.
I think even Johannes told me If I connect 2 axos via midi I can avoid the "classic" midi circuitry.

Using PA2 and PA3 for extra midi definately works as I have found this working myself, but I did find a bug in it, when you change patches when running the Axo in standalone mode, it appears the midi through PA2 and PA3 disconnects. This may not be an issue for you if you don't plan to change patches in standalone mode.

I don't change patches atm, so that's not an issue. And If want to do so I would have 2-3 patches max, so I could just load different patches to sd cards.

My recomendation is to either use midi splitters or wait for the midi support via SUB hub to be implamented. I guess there may be other options as well, but recom,end the opotocouplers are there for a reason and have been part of the Midi hardware for a long time for our own benifit. There are vmany websites etc, that give the relevant circuits if you want to do your own optocoupler circuit etc, so may be worth reading some of these.

I would rather need a midi merge. Midi out via PA2 --> axoloti midi out worked fine.
USB hub support would so much simplify all these things. You could for example add usb midi interfaces, have one axoloti host the other + use your favorite usb midi controllers.

But the point is eventually: I don't use axolotis midi circuitry how can I use the midi input part with PA3 to receive midi?

[Gavin]

You can only avoid the clasic midi circuitry if both are using the same power source.
For example, if both are powered by the same power supply, this can be OK, but if each has its own power supply, this is not healthy, this is why midi input is isolated.
If its working for you, then good job. Be careful. !

[Hugo]

Great you figured it out! And thanks for all the info @Gavin!

Using PA2 and PA3 for extra midi definately works as I have found this working myself, but I did find a bug in it, when you change patches when running the Axo in standalone mode, it appears the midi through PA2 and PA3 disconnects. This may not be an issue for you if you don't plan to change patches in standalone mode.

This is working out for me. Are you still interested in this?

[Gavin]

Thanks @Hugo,
I am very interested in sorting the issue, my work around was to connect the serial line directly to the MIDI in DIN o the Axo.
So my setup is that I have a menu patch just for connecting to other patches.
When setup via UART, if I start in the menu patch, the link works, the moment I go into a sound patch, it stops working, and vice versa, If I start in a sound patch it works, the moment I go into the menu patch it stops working.
I did as much testing as I could to try and work out where the problem is, my understanding of the midi code in the Axo is a little limited, so I kept this testing basic, but from the midi source, I am sending the serial data from Arduino Due using the "fortyseveneffects" library, and I was very thorough in this testing, what was happening, is the midi data was being sent, but was not being processed when it arrived.
The serial input on the Axo works fine, even testing with the serial factory patch all worked perfectly. It all works perfectly connected directly to the axo midi in din.
So based on all this testing, I can only guess with my limited experience, it is somewhere that maybe missing a startup routine when opening a patch in standalone mode that is preventing the midi from flowing through, maybe even something happening to the serial pin itself. But one downside, is I won't be in a position to test it for at least a few weeks, because I am working on another section of the project, and so my standalone setup to test is currently out of action.
But any thoughts you may have on the problem will be great.

[blademn]

Hello, thanks for all the wonderful information on this thread. Does anyone happen to have a simple example patch of how to receive midi in from PA3?

[trimardius]

I guess this is what you are looking for:

hug/midi_io/extra_midi_io.axp

In the contributions folder...

[blademn]

oh thank you so much for pointing this out! its such a deep community library, I appreciate the navigation assistance.