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Help With Trinket M0 Project

Posted: Thu Jul 14, 2022 8:23 pm
by conderjscott
Forum Folks,

I have a MIDI foot controller that I want to use with a guitar amp. The amp has a USB port but no MIDI DIN connectors. Both have USB-B "device" connectors only.

Using adaptors to connect the controller directly to the amp did not work. So I started reading about the need for a MIDI controller in between.

As a test, I ran the foot controller via USB to my PC and used a MIDI utility to echo it out to the amp via USB. That works great, but it was only for testing purposes. Carrying a PC around to go in the middle is not worth the effort.

I found a project on the hackaday site called "USB Host MIDI for Two" that uses two Trinket M0's to do what I believed I needed to do - provide host controller functionality to both of my devices.

I built the device and went through flashing the Trinkets to the best of my understanding using a file I downloaded from the github project. But it's not working with my devices.

I must admit that I'm very limited in my programming ability. I know that you guys did not post the project, but the person who did has not responded to my inquiry. So I thought I would see if someone here could take a look at the info on the github page for the project and see what I might be able to do to get it working. You guys would know more about what you're looking at than I do.

Here are some points that left me uncertain:
  • On the project home page there are two links for firmware. But, as far as I can tell, you can only flash one file to the Trinket M0's. So I'm not sure if I downloaded the correct uf2 file from github or if I was supposed to somehow incorporate more than one. I downloaded the file MIDIUARTUSBH.ino.trinket_m0.uf2 from this page.

    I can connect my foot controller and run MIDI CC into the project from either Trinket and I can see pulses on the UART TX lines using an oscilloscope. But apparently the Trinkets don't put the MIDI commands out the USB connector.

    There is a revision of the code called "Update USB host MIDI to make MIDI thru controlled by pin 0." I have tried grounding pin 0 since it looks like that's required to pass thru MIDI. That didn't fix the problem.
So I would appreciate your help getting my project working more than you know.

Thanks.

Scott

Re: Help With Trinket M0 Project

Posted: Fri Aug 19, 2022 9:39 am
by FailingTinkerer
I think you downloaded the right file.

Do you have a picture of how you wired up the two M0's?

Do both trinkets run the same file?

As far as I understand it works like this:
[Midi device A] -usb-> [M0 A] -UART-> [M0 B] -usb-> [Midi signal]

MIDI 2.0 is bidirectional, so if you're using MIDI 1.0 it probably won't work.