BBC Micro:bit review – the free Raspberry Pi rival for every Year 7

Unveiled back in March 2015 as part of the BBC’s Make It Digital initiative, the Micro:bit marks the corporation’s first foray into computing hardware since the much-loved BBC Micro in the 1980s. Unlike the BBC Micro, however, with its distinctive black-and-red mechanical keyboard, the Micro:bit is a tiny device designed to be used with existing computers.

With an array of built-in sensors and a 5×5 LED matrix display, it’s designed to get kids thinking about physical computing and, following a redesign and some issues with the power circuitry, starting this month every Year 7 pupil in the UK is going to get one for free.

Specifications

It would be easy to make a comparison between the Micro:bit and the Raspberry Pi, especially since the launch of the £4 Pi Zero. While both are low-cost devices designed for education, however, there’s a definite difference: the Pi is a microcomputer, a modern incarnation of the BBC Micro of old, while the Micro:bit is a microcontroller.

The Micro:bit is powered by a Nordic Semi nRF51822 SoC processor, which bundles a Bluetooth LE radio with a 32-bit ARM Cortex-M0 CPU running at only 16MHz and with just 16KB of RAM. Interestingly, this isn’t the fastest processor on the board. A second chip, a Kinetis microcontroller, has a 48MHz Cortex-M0+, which is only used as a bridge between the Micro:bit and a USB-connected computer.

The Micro:bit also includes a pair of onboard sensors in the form of a magnetic compass and an accelerometer, giving it basic positional and gesture-recognition capabilities. There’s a pair of buttons, plus a reset button at the rear, a 3.3V battery connector, and the front is dominated by a 5×5 matrix of 25 red LEDs – the only display available to the device.

Layout

Back when it was it was first announced, the BBC’s device shared the same characterful layout as the CodeBug, the device that inspired it. Since its redesign, though, the Micro:bit has become much more businesslike. A tiny rectangle with rounded edges, the board measures not much more than a pair of SD card cases side by side.

The rear of the board, where the processors live, includes a silk-screen layer labelling most of its components. Oddly, though, the Kinetis microcontroller is left unlabelled. Flipping it over reveals the LED matrix and the Micro:bit’s primary means of interacting with external hardware: a 25-pin edge-connector for general-purpose input/output (GPIO) operations.

Five of these pins are enlarged for use with crocodile clips or banana plugs, providing three input or output pins with analogue-to-digital conversion (ADC) and pulse-width modulation (PWM) support. This means they can do everything from reading data from moisture sensors to controlling a connected stepper motor or servo, along with a 3.3V and ground pin. The remaining 20 are slimmer, and designed for use with expansion boards such as the Kitronik Edge Connector Breakout Board.