A Raspberry Pi Zero fits neatly onto the rear, although you’ll need to be careful when mounting it not to crack the screen – it’s best to put it face down on a soft surface. Short standoffs (not supplied) can be use to secure it. If using a full-size Raspberry Pi, you’ll need a GPIO booster header.
While the HyperPixel 2.1 Round uses all the GPIO pins, five breakout pins on the rear provide the option of connecting sensors via an alternate I2C interface.
Libraries for C++ and MicroPython can be downloaded from Pimoroni’s GitHub repo. The latest version of Pimoroni’s MicroPython UF2 firmware contains the necessary drivers, so you’ll need to flash Pico with it.
To help you get to grips with the picowireless library, a couple of MicroPython examples are provided. One creates a simple web server enabling you set the red, green, and blue values of the on‑board LED. The other demonstrates connecting to an API and lets you control the LED’s colour using #cheerlights tweets.
Both examples are pretty verbose, with some complex HTTP request details, so are hard to follow unless you know your networking, but you could easily adapt them for your own projects.
Alternatively, you can code with CircuitPython, using Adafruit’s CircuitPython and ESP32 libraries, by adjusting a few pin numbers in their code examples.
If you really want a round display, maybe for a Halloween animated eyeball, this is an excellent option.