Teensy Midi Processor + CV Out

A.b.

New member
Hello,

I have a question about a circuit diagram because my builidng experience of such cicuits is clearly too rusty to create anything good right away.
I hope now that you can help me out.

I would like to build a midi processor with a Teensy 4.1 board that has 8 midi ins + 8 outs as well as midi via USB, between which I can route, filter, change the midi signals etc.. Master clock and possibly the pitch of some channels should be able to be output later as CV (at dedicated outputs), but this is not yet taken into account in the sketch, since the basic functions of midi routing and processing should work first. This is only important later for the power supply, since in that case an additional power source must be planned in any case.
(A solution that can be bought directly is not available for me at first, less because of the costs, but because I have to tailor the Teensy Middi hub to a modular system, e.g. add several switches and pads later, etc.)

The circuit diagram for the first version of the midi circuit is attached:
Midihub 1_Schaltplan.jpg


I created this according to the basic scheme for midi ins and outs and multiplied it accordingly. My question here is just: Would it work like that or was there something I didn't think about at all? Are there points at which the circuit has been improved, e.g. because it can be minimized or made safer?
I am thankful for every hint!
Best regards,
A.b.
 
Hi MarkT,

thanks for your reply! I now have added te pull-up resistors to the circuit and added also 470K resistors between the Pin 7 and GND and a Capacitor between the VCC and GND of each OC. I hope this makes more sense now :D

Midihub 1_Schema_6n138.jpg

Regarding your linked article, which was very helfpul, thanks for that, i also made a seccond circuit which uses the H11L1 as an optocoupler. I am still not sure if i haven't forgott something in the layout. But with the H11L1 it seems to be easier, cheaper and less parts to include. That would be great!
(In the schematic there is the wrong part, as i couldn't fint the right one for Fritzing)

Should this optocoupler also have a capacitor at the Vcc?

Midihub 1_h11l1_Schema.jpg

Another question belongs to the max Idd of the Teensy GND. How much current could the Teensy GND handle? I only found the information on the datasheet for the 3.6, where it says it could take up to 185ma, but i couldn't find it in the datasheet of the Teensy 4.1 nor somwhere here in the forum.
Sorry if this is a dump question!
Regards,
Abb
 
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