Requirements

You will need to be comfortable doing the following:

• Soldering, unless you buy a Pico WH with the headers pre-soldered

• Crimping, unless all your LED strips have connectors suitable for a breadboard pre-crimped onto them

• Wiring a mains power lead to a power supply; this just means some wire in some screw terminals, but you need to be confident you know which wires are live, neutral, and ground. If you’re not confident (and/or competent!) in this, please get help from someone who is.

• Using SSH, preferably using pub-key authentication

• Running commands at a Linux command line

• Editing a text configuration file from the Linux command line using nano, vim, or your favourite console text editor (you can try copying stuff back and forth, but given there’ll be some user switching involved you are much better off just being able to edit things at the command line)

Shopping List

You’ll need the following bits of hardware to follow this tutorial. Don’t worry if you have fewer neopixels, or a slightly different model of Pi. Hints on adjusting the instructions to other configurations will be included along the way:

• A Christmas tree

• A WiFi capable network

• A Raspberry Pi; I’m using a 3B+ but any model [1] with a CSI camera port should work

• A camera for your Pi; I’m using an old v1 camera module, but you can use later models [2] too or even a web-cam [3]

• An SD card for your Pi; I’m using a spare 32GB SanDisk Ultra card

• A power supply for your Pi; micro-USB for models older than the 4B, USB-C for the 4B or later

• A Pico W, or some variant thereof (including a Pico 2W, Pico Plus 2W, etc.); note you need a WiFi capable variant (not the bare Pico), and that this project relies on the Pico’s specific capabilities [4]

• A breadboard large enough to mount your Pico and all associated wiring

• A momentary push-button suitable for mounting on a breadboard

• A red LED

• A 330Ω resistor

• Jumper leads or solid-core wire

• A 5V power supply capable of driving the Pico (easy) and all your neopixels (harder); a typical micro-USB supply is not going to cut the mustard here but I’ll go into more details below

• As many strands of WS2812 or APA102 compatible neopixels as you can reasonably fit on your tree; note these do not have to be the same model, RGB ordering, or length

• Whatever attachments you need to connect your neopixels to your Pico or your carrier board; if you’re lucky your strands will already have compatible connectors attached, if not you may need to solder and/or crimp some on yourself

• A box made of a non-flammable material large enough to house the power supply, breadboard, and all associated wiring

• Some cable glands large enough to accommodate at least the mains cable, and optionally the neopixel cables

• A couple of cable ties

In this tutorial I’ll be using an 63-line breadboard with two separate power rails which is probably overkill, but I don’t like being cramped when wiring things! For the neopixels, I’ll be using a 50-LED strand of RGB WS2812 neopixels, and a 100-LED strand of GRB WS2812 neopixels because that’s what was lying around.

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[1]

Note this set up has not been tested on a Raspberry Pi 5, on which the legacy camera stack does not work. The gstreamer camera stack may work on this model (in future I should add a libcamera based option).

[2]

Note this has not been tested on a v3 camera module which is incompatible with the legacy camera stack. The gstreamer camera stack may work on this model (but again, I should add a libcamera based option).

[3]

Note that web-cams typically have much lower resolutions than Raspberry Pi camera modules, and higher resolutions are better for calibration.

[4]

This project won’t work out of the box on other microcontrollers as it’s using the Pico’s PIOs to drive the neopixels. That said it’s not hard to adjust the Pico’s scripts (they’re just MicroPython) so if anyone wants to try making it more generic, feel free!