Raspberry Pi Pico MIDI Module PCB

I’ve now built several DIY Raspberry Pi Pico MIDI interfaces, and despite several hints via social media, no-one has come forward to make me a simple MIDI interface module, so I’ve decided to have another go at making a PCB myself.

Update:

• Find the Build Guide here: Raspberry Pi Pico MIDI Module PCB – Part 2

Warning! I strongly recommend using old or second hand equipment for your experiments.  I am not responsible for any damage to expensive instruments!

These are the key tutorials for the main concepts used in this project:

• PCB Design in KiCad from Arduino Uno Dual Merge MIDI “Shield” – Part 2.
• Ordering your PCB: a Beginners Guide for Manufacturer Options

If you are new to microcontrollers, see the Getting Started pages.

The Circuit

I’m using the same MIDI IN/OUT for 3V3 microcontrollers that I’ve now used many times before.

Note that the capacitor should be 100nF not 100uF.

The Design

I won’t go over the “notes to self” about carrying out the design process, you can read all about that in my previous project.

Here is the thinking behind this new board.

• I wanted something a little like the Adafruit MIDI Feather Wing, but rather than try to squash everything into the same footprint as the Pico itself (like Pimoroni do with their “packs”) I opted to have the MIDI sockets off to one side.
• I experimented with a “left hand” and “right hand” version, but went “left handed” as this would allow me to use the interface alongside the Pimoroni dual extender and something like the Pico keypad.
• I did wonder about breaking all all the IO too, but opted for simplicity.
• I have given the board the option of using UART0 on GPIO0/1 or UART1 on GPIO4/5 via a jumper (which could be replaced with a low-profile switch).
• I opted not to bother with a THRU port (or headers to provide one), again going for simplicity.
• I was originally going with a 52mm square board, but then expanded it slightly vertically to allow me to route tracks around the Pico.  With narrower tracks, I might be able to route between pins, but I didn’t see the need.
• I originally was going to use solder bridges for the UART selection, but whilst there are footprints and symbols in KiCad for these, I just couldn’t get them working.  There seemed to be some conflict between the PCB constraints and design rules checking and the footprints and I just gave up trying to sort it out, so jumpers it is!

I started using the Raspberry Pi Pico footprint, but that is really designed for times when you want to solder a Pico directly to your board.  In the end I used pin-connector/headers but made sure they were aligned to the mechanical dimensions of the Pico (obtained from its datasheet).

Production

As a consequence of my last board from Seeedstudio Fusion, they offered me a voucher to use again, so I’m using that and sending this one off to them too.  I had no complaints: their service was relatively cheap, pretty quick, and quite painless and the quality of what I got back seemed perfectly fine to me (not that I have anything to compare it with of course!).

Anyway, the design is now “live”, so I’ll report back with a build guide when I get the boards back.

I still haven’t decided how best to publish PCBs yet, so if this is something you are interested in, for now the best thing to do is to ping me a message somehow.

I’d like these to all be open designs, but just haven’t decided how to do it yet!

Closing Thoughts

I pleased to say I haven’t forgotten my KiCad!  I have a few boards I’m now interested in designing, so expect to see more of this in the future.

Kevin