This project was originally intended as an entry in the 2021 hackaday Designlab contest. It was totally too ambitious, given that university was taking up most of my time. I am currently working on (or procrastinating from) my master's thesis, so I won't have time to continue this project until July. But I want to put it out there, even in its current state. Unfortunately I haven't made any demo of the modules yet.

I do feel like the name is a bit too generic, since people may refer to any MIDI connection as a "MIDI bus". Also, there are a couple other projects with the name. Maybe the name should be changed to CAN-MIDI, or Modular MIDI (M2IDI), or something else.

Firmware status:

The code is a mess. And I have not used a bootloader so far, because the bootloaders need a button to activate.

CV module: Turns out programming flexible firmware is difficult, so the menu does not work yet. But most of the other features are present to some degree.

USB module: I have not found a perfect USB driver, and the notion of writing a driver is intimidating. This firmware has practically not been started.

DIN and Tangle: Are mostly done.

MIDI driver: MIDI 1.0 and 2.0 parsing is implemented, as well as conversion between these formats. However, their compliance with the standard should be double checked. Other features like capability exchange are not implemented.

Hardware status:

A couple issues were found after the PCBs were ordered. These should be mentioned in the CADLab annotations.

The USB-C connector's footprint was not within the capabilities of the PCB fabricator, so I had to reduce hole sizes. This means they are a bit tight. They also require thinner (1.2mm or less) PCBs to be soldered properly. I will probably change these to connectors with SMD pins for data and power, and through-hole for the shield to help with mechanical strength.

I discovered that the ATSAMD21G MCUs don't have an integrated EEPROM, they have flash as emulated EEPROM. Which isn't ideal, so I will likely add an external chip to save settings in.

The MIDI out on the DIN module does not work because its signal is inverted. This happened because the MCU I used in the previous version (Attiny406) could invert any pin's function from the firmware.

According to the ATSAMD21G datasheet its internal oscillator has too much jitter to be used in a (compliant) USB host, and it's recommended for USB devices as well. So it will need an external crystal. I should have discovered this before ordering the PCBs, it was in the schematic checklist.

The USB module has decent DACs and ADCs which in some situations wouldn't be used as an audio interface. It can be cool to add more RAM to this module so it can be used for delay and reverb effects if people want.