Midi clock, start and stop not detected by Midihub input


I have a DIY project for sending midi start, stop and clock messages via Din connector (classic serial MIDI not USB).

I’m using an STM32 nucleo board coupled with a Sparkfun midi shield as setup. I’ll call this “DIY setup” for simplicity.

The start, stop, and clock messages sent by my “DIY setup” are successfully received by my MPC1000 and other machines (they start, stop and run accordantly).

How ever, using the same setup the messages sent are not recognized on the Midihub input: The midi monitor window does not show anything and the LED does not blink. I’ve done a few A-B testing with other gear to be sure that the Midihub input port is active and the midi monitor window correctly selected.

I’ve also tested mi DYI bundle connected to the midi input of a NI Audio8 soundcard, connected to my PC running Pocket MIDI software as monitor and I get the corresponding “FA, F8, FC” messages and BPM.

Do you know why the Midihub input is not getting the messages successfully?

Thanks in advance!

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Hey @pvasquez , just to check:

when a MIDI cable is run from the MIDI-out of “DIY setup” to any of the four ports on the left side of Midihub, no LED flashes when a message is sent?

What about when a cable is connected from any other device to MH?

Hi @resonotter

Thanks a lot for your quick reply!

To be 100% accurate I believe I only tried ports A and D on the left side.

It works as it should be, I see the messages in the MH monitor window and the LEDs blink according to the channel that is receiving.

OK, Pablo, thanks for that.

Aside from checking it with every port and different MIDI cables (just to be sure), I think this is one for @Giedrius!

It might be useful if you have a way of recording the MIDI stream out of the “setup” so that G can have full details of what MH is receiving but clearly not liking. (the forum allows posting of .mid files; other formats you can archive & upload the .zip)

Good Luck (and welcome to the forums)! :hand_with_index_finger_and_thumb_crossed: :+1:

PS the Sparkfun sockets are classic 5-pin and not TRS, right?

Thank for your feedback!

I did some more tests:
It is not a cable problem: I tried 2 different cables and they both work with the DIY setup output to my MPC MIDI input but they are not recognized by any of the 4 inputs on the MH.

And yes, it is a classic 5-pin DIN output on the Sparkfun MIDI shield, not TRS.

I will try to get raw data from the UART for @Giedrius soon, I don’t have a FTDI converter with me at the time.
I could use the integrated UART in the Nucleo board that is sent via de micro USB port. If I output the same data through it, so different UART port out but same messages and baud rate is it good enough?

In the mean time I did a video of my problem, hope it helps to make it clearer.
Here is the link: https://youtu.be/DHrOgs-AUoQ


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I’m no expert, correct me if I’m wrong? but the Spark fun midi board looks like it is for use with 5v I think… The STM32 is 3v isn’t it? Maybe the 220Ohm resistor on the Midi output may be a bit too large. Perhaps it’s just enough to just about drive your MPC, but not quite enough for driving the MH? Just a guess…

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This is a good point indeed.
Even though the nucleo board claims to be “Arduino compatible” the UART is directly connected to MCU pins in both cases, arduino and nucleo.
The STM32G0 (nucleo) can output 3.3V max.
The ATmega328 (arduino) can output 5V max.

This might be the reason…
I will try to buffer the uart output from the STM32 and see if it makes a difference.

Thanks for the suggestion @submo !

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Cool… If that’s the case, just dropping the 220ohm output resistor to something like 56 ohms should work. Might also wanna double check the resistor values at the Midi In. Not sure if the STM32 pins are 5v tolerant. Like I said I’m no expert, but do like to tinker now and again :slight_smile:

Edit: just found my Sparkfun midi board and realised those SMD resistors are a pain to replace (I thought they were through hole on that board).

Hey, make sure to follow the MIDI Electrical Specification when implementing DIN-5 ports.

It’s possible to have 3.3V output, and use it with 5V based MIDI implementations, you must use different Resistor values. All the details are in the spec. :slight_smile:

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Thanks @Giedrius !
As @submo also pointed out, it was a resistor problem.
Now I’m using the correct values and it is working as a charm :slight_smile:

I always though the MH was a great product, but now I can say it also has great support and community around it!

Cheers everybody!