Pico Touch Board PCB Design

By Kevin on March 2, 2025

Ever since doing my Raspberry Pi Pico MIDI Touch Keyboard I've wanted something that would be crocodile clip/DIY friendly, so this is the result.

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

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The Circuit

This is based on my Raspberry Pi Pico MIDI Touch Keyboard PCB Design with the key changes being the addition of headers to break out the Raspberry Pi Pico's GPIO pins, and touch pads on all GPIO.

The design includes the following:

GPIO touch pads on all Pico GPIO ports using the "single resistor to GND" design that seems pretty common these days.
MIDI IN and OUT with options for DIN or TRS sockets.
7-12V input via a 7805 regulator to produce 5V power for the Pico's VSYS input.
VSYS protection diode as per the recommended Pico power circuit.

I've also included a couple of solder jumpers which can be used to bypass the regulator (when not fitted to the PCB of course), to get a 5V feed direct from the barrel jack, and another to connect AGND to GND if required.

PCB Design

The following requirements drove the design of this PCB:

Large crocodile-clip friendly pads.
Lego dimensions for holes and spacing. I mean, why not?
Choice of either MIDI DIN or TRS sockets.
Optional power circuit for 7-12V input via a barrel socket.
Optional USB power.
Option for direct 5V input via a jumper header or the barrel jack socket.
USB MIDI.
All GPIO broken out to headers for non-touch pad uses if required (i.e. if the accompanying resistor is omitted).
ALG IO pins especially are highlighted in case they are required for additional IO.
Keep to less than 100x100mm board size.
Pico can be removable using optional header sockets or soldered down using castellations.

Closing Thoughts

I think I've managed to incorporate everything I wanted into this board.

I'm particularly pleased to have taken the time to include Lego-compatible holes in the design. I'm not sure what my plan for those are yet, but I was quite inspired by the approach used by their use in Brown Dog Gadgets Microbit Crazy Circuits, so thought I'd give them a go...

Kevin