3

PICKING

THE Perfect

LENS

Above

The ST

Microelectronics

STM32F072, a typical

inexpensive Mbed

board featuring an

ARM Cortex-M0

Tensilica core and full WiFi connectivity, and comes

with a TCP/IP stack allowing it to be very easily

connected to the internet. What brought it to the

attention of our community when it arrived in 2014

was that it is extremely cheap, costing only in the

region of a few dollars each in single numbers to

hobbyists. A huge effort was undertaken

to create open-source tools for it, despite

its only having limited documentation at

the time. The ESP8266 is usually to be

found on a series of standardised

modules intended to be fitted by the

million into Chinese-made IoT devices,

and many consumer products such as

ESP8266 IoT light switches have been

repurposed as development systems with

ready-attached power control hardware.

More recently, though, these modules have appeared

on more conventional development boards. It’s fair to

say that the world of ESP8266 devices is something

more of a Wild West than the others we’ve

mentioned, but the low price – especially when you

consider their WiFi connectivity – makes them an

extremely interesting option.

Having considered microprocessor architectures, it’s

worth taking a moment to look at how microcontroller

boards are programmed. It’s easy enough to say

that the majority of them use a serial link

while others use USB and a few of them

appear in your operating system as a disk

drive, but that conceals an important point

MBED, AN ARM

FOR ALL SEASONS

Mbed is a combination of software development tools, on-

chip OS, and reference hardware designs for the various

ARM microcontrollers. It can be thought of as ARM’s

answer to the Arduino ecosystem, with the important

distinction that ARM itself does not produce

any Mbed boards. Instead, just as it licenses

the processor cores to chip manufacturers,

each of those manufacturers produces its

own Mbed-compatible platform for its chips.

This provides Mbed with the extremely useful

feature of being available on a huge variety of

boards, each with its own features depending on

what the manufacturer has included on the silicon

alongside the ARM.

Development for Mbed is through the medium of C or

C++, and there are two development routes. One is through

an extremely easy-to-use web-based IDE, while the other

is a more traditional command line-based compiler that

allows you to use your IDE of choice if you have one.

Mbed boards are available at all budgets depending

upon the capabilities of the microcontroller in question.

The ST Microelectronics board pictured, for example,

cost well under ten pounds and provides an Arduino-

compatible shield footprint for its Cortex-M0 processor.

Above

The in-browser Python editor for the BBC micro:bit is a fully

functional development environment that does not require any

other software beyond a web browser on school computers