The Circuit Playground Express (CPX) is a programmable microcontroller board that makes it really easy to get started. Plug it into a computer with a micro USB cable and you’re ready to start coding. The UF2 firmware takes software into the board in two ways: either you can press the reset button to enter programming mode and copy UF2 files into a new drive that will appear on your machine, or you can upload directly from the Arduino IDE. For beginners the first method will be easier, as you can generate these UF2 files from either the web-based MakeCode block-based editor or from a Circuit Python development environment.
On some versions of Windows, you’ll need to install drivers, but on Mac OS X, Linux and Windows 10, you don’t need to install anything if you use MakeCode – just plug your board into a USB port, then point your browser to makecode.adafruit.com to start your first project.
From here you can take advantage of the wide range of hardware that’s packed onto the board. For output, there are ten NeoPixels and a speaker (not just a buzzer). For input, there are two buttons, a slide switch, an accelerometer, a temperature sensor, a microphone, and a light sensor. With all this, you can put together some pretty fancy projects straight away.
For our first project, we made an indicator for cyclists. It uses the large holes on the CPX to attach it to the back of a cycling glove, then uses the accelerometer to recognise when the hand is held out indicating a turn and flashes the NeoPixels orange. This took 18 lines of dragged-and-dropped code in MakeCode and no additional hardware (most of these were to ensure that there was a stable reading from the accelerometer). While it’s hardly a complex project, it shows that you can build useful projects quickly with no additional hardware or software.
There’s nothing on the Circuit Playground Express that’s fundamentally unique – you can get the same sensors and outputs to attach to virtually any microcontroller. What makes this board special is the way it’s brought together into a single package. It’s hard to think of any project where you’ll need all the features available, but given the £25 price tag, it’s easy to justify the cost even if you only need one or two of the extra input or output options. By bringing them all onto the main board, there’s no extra setup or wiring, and it’s all supported by the software without having to add any libraries, which again makes it thankfully easy to get started.
The one obvious thing missing from the device is any form of networking. It does have a built-in infra-red receiver and transmitter, I2C and UART, but no WiFi or Bluetooth. The other major limitation of the board is that it’s not breadboard-friendly – it’s far more suited to crocodile clips or banana plugs.
Many, many possibilities
Whether or not these are really limitations depends a lot on the sort of projects you’re working on. The CPX isn’t going to work well for Internet of Things-type applications. It’s also not going to work well as a controller for building complex circuits – having just eight GPIOs limits the amount of hardware you can connect. Anyway, there are lots of microcontroller boards far more suited to these uses.
However, the CPX makes it fantastically easy to get started with embedded and physical computing projects. You can build on the integrated hardware with the eight GPIOs. Seven of these can detect capacitive touch input, so to add more user input to your project, you just need a few crocodile clips and leads. As all the GPIOs can read analogue input, it’s also trivial to add input from and device that gives a varying voltage as it’s output. There are also five PWM output pins for driving LEDs at different brightnesses. The MakeCode platform is a code repository as well as an IDE, and there are a set of tutorials from Adafruit to help you get started with the platform and the hardware.
The CPX is well suited to people getting their first microcontroller, either buying one themselves for fun or as part of a taught course. For this purpose, it’s genuinely hard to fault the CPX. It’s easy to learn with no (or minimal) software to install, yet at the same time allows you to use more advanced languages if you’ve got the knowledge and experience. It packs a fantastic range of input and output options onto the board, which means that you can dive right into some more interesting projects without getting immediately bogged down in attaching extra hardware. It’s also easy to start to build simple circuits off using crocodile clips.
Perhaps the ultimate test of any bit of hobbyist kit is whether or not it sparks excitement. For us, the CPX gave us a childlike sense of glee, because it makes so much so easy. This is great for beginners and any hobbyists who like to quickly prototype projects.
$24.95 / £25 adafruit.com (US) / pimoroni.com (UK)
The best microcontroller board for introducing people to physical computing projects.