Pico and expansion board

Got my V3 full kit and everything is up and running after a bit of soldering … and nothing else. Kudos on the continued amazingly smooth out of the box experience.

I love how the pico dangles on the end of the LED strip. I read somewhere that its pads could be hacked to connect to the sensor board, but I just need to add an accelerometer. Is there a simple way to connect just that single part to the pico?

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I wish, as I want the same.

Hi @sorceror,
The small round programming pads have what’s needed for the sensor board. Though it wasn’t designed to fit, it’s possible to wire up. You’ll need GND, +3v, and the RX pin on the PB, these are labeled just G, 3V, and R. Given the limited connectivity, there’s not really a good way to interface one other than that.

The sensor board doesn’t yet come in a smaller Pico form factor, though I keep hearing from folks that would love accelerometer and/or sound with the Pico and would love to make one, though I don’t have a timeline on that.


Thanks @wizard! The connection sounds simple, but the bulk of the sensor board is still a blocker when I just need a single sensor. FWIW, I am making a motion-activated sword with 2x144 LEDs (these SK9822s are amazing!!) in an acrylic tube and … well … the motion sensor has to be at the tip of the sword for it to be of any use!

As with any product, it makes sense to gauge interest before making anything … so here is an idea: I have been doing Kiwi crates and now Tinker crates (https://www.kiwico.com/tinker) with my kid and I was thinking that a PB pico would be an amazing seed item for their line of monthly kits. Like … with an annual subscription, you get a PB pico (perhaps with a couple of sensors onboard wink) and 1m strip of LEDs, then each month a construction/coding activity. Maybe worth poking KiwiCo to see if they want to hook up with you. I think it would be a great match for their more advanced customers, and a way to fund a big manufacturing batch for you!

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So I’ve said a Pico+ (Pico with motion and sound sensors) would be great before.

However, the issue is that the sensor board has an independent processor, it’s an STM32F0 ish cpu. The sensor board is open sourced so someone could adapt that board (or make a compatible one that did the same protocol)

To add the motion and sound sensors directly to the esp32 on a presumably new Pico+ would require Ben to add code that not only gets the data but also does the FFT processing for the sound. Doable but not trivial (especially since the goal is enhance performance, and the v3 does that, way faster than v2, so suddenly slowing down again isn’t going to be acceptable)

Realistically, he’d have to add a coprocessor to the Pico+, replicating the functionality of the sensor board.

I’m in the same boat: the Pico is so tiny, and yet adding sound / motion is neither trivial nor tiny right now.

Honestly, I suspect our best bet, short term would be to see if a stripped down (or just re-layedout?) sensor board could be made that matching the tiny dimensions of the Pico. Removing the aux jack, for one. If someone takes the eagle files Ben has in the GitHub repo and resize it from a square to a Pico matching narrow layout, potentially either Ben could make it, or we could order custom PCBs.

You’d still have to solder tack to the 3 pads on the Pico. I’m curious why (and this is a question for @wizard), there is so much “empty” space left on the Pico (on the right hand side of the PCB), and yet no castellated pinouts on that side.

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I had explored doing the audio directly on the ESP32 briefly during early V3 prototypes and exploration, but ran into quality problems. Any time the radio fired up, the ADC had lots of terrible buzzing noise injected. Might have been an issue with the WROVER module design I was using in the V3 Pro prototype at the time (the kitchen sink of V3s). It might be solvable with time, or a non-issue for the pico SoC.

The space on the right side is all about radio antenna clearance. There’s a keep-out zone just to the right of the button, and adding anything - traces, components, etc - will mess with the antenna.

Double sided assembly would let me cram a lot more with the same board size, but this adds to assembly complexity significantly. A pico-sized expansion would be hard to solder. A longer Pico might work well though. Most feedback I’ve had is about keeping the width small, rather than the total length or thickness.


@wizard, what if you made an smaller expansion board and either exposed the connections it would need on it and the Pico or put a small connector on each that you could connect the two boards? If you could shrink the sensor board or make a special one with reduced functionality you might be able to fold them together at the connector and it might be roughly the same since as a double sided pico. Or maybe have them connected by I2C? and the user can decide how long of a cable they want.