Making light work of 'wireless wires' for the Internet of Things

Maxine Hewitt
Business Development Director
Making light work of 'wireless wires' for the Internet of Things
Maxine Hewitt of Alpha Micro Components looks at how ready designed and built RF modules can help bring connected products for the Internet of Things to market faster.

The emergence of the Internet of Things (IoT) is spurring the development of a new generation of radio technologies that can act as bearers for the network connections that turn a standalone ‘Thing’ into a full participant in an IoT ecosystem.

Many such devices, be they sensors on critical infrastructure such as bridges, distributed air-quality monitors in our cities, or even children’s toys, will be expected to work for weeks or months with little or no user intervention. They’ll also have to use widely available radio spectrum, and manage the creation and maintenance of their connections to wireless infrastructure, again ideally without user intervention. So low-power operation and easy connectivity management are vital.

As you might expect from the name, Low Power Radio Solutions (LPRS) produces a range of products that can be dropped into an IoT design to enable wireless connectivity using widely available spectrum and minimal power.

The eRA400TRS and eRA900TRS easyRadio Advanced modules operate at either 402-470MHz or 804-940MHz, respectively. They include an RF transceiver, a microcontroller and a voltage regulator, and are intended for applications such as smart lighting and heating, home automation, remote sensors and security.

The rationale for using such modules is to get a product to market more quickly than would be possible by building your own RF interface. To that end, the modules are designed to be simple to implement. They are produced in a nine-pin single in-line package of just 38 x 14 x 4mm, which makes them easy to integrate with the rest of a design.

The electrical interface is simple as well: two ground pins, VCC and antenna, and then serial data in and out pins (which should be connected to a UART), a carrier detect pin, plus Ready and Busy signals.

The devices can be controlled using the easyRadio programming protocol that LPRS has established. This provides a simple way to set characteristics such as communication speeds, RF power levels, channel settings, bandwidths and the band plan. Alternatively, the modules can be used in a raw-data mode that doesn’t rely on the easyRadio protocols.

The total radio spectrum that each part can address can be broken down into a number of channels, and the channels can be of varying bandwidth. This means the modules can support up to 132 channels, which can be traded off against channel bandwidths ranging from 150kHz down to 12.5kHz (which in turn controls the available data rates).

LPRS also offers the eRA400TS and eRA900TS, which operate at 433MHz for UK and European markets, and 868 or 915MHz for European and US markets.

It’s good to be able to use pre-built RF interfaces to speed the development of IoT devices, but it raises the question – what’s at the other end of these RF links? Are IoT device vendors also going to have to develop their own widely distributed RF networks to connect these devices to the Internet?

It is little surprise that a couple of solutions to this problem have already emerged.

Sigfox is an IoT interconnectivity service, which aims to help IoT ecosystem developers avoid having to deploy their own radio networks to connect their IoT Things.

LoRa is an industry alliance that has set a global standard for low-power point-to-point and wide-area networking technologies to support IoT connectivity. The alliance’s website says that 37 operators have committed to the standard, and that more than 250 trials or city deployments of LoRa networks are already under way.

LPRS has responded to the emergence of these networks with the introduction of its eRIC ISM/LPWAN modules. These are designed as a family of interchangeable modules working to the easyRadio, Sigfox or LoRa protocols.

The 15 x 20 x 2.2mm surface-mount modules share the same pin-out, so designers can produce one printed circuit board and swap out the RF module to match the chosen connectivity standard. The modules include an RF transceiver, RF band-pass filters, a microcontroller, 32KB of flash memory, a temperature sensor, and a low-drop voltage regulator.

The modules include an embedded operating system that manages all the complex radio functions and so does away with the need for the user to program multiple control registers and understand their interaction. The on-module flash memory also has a partition for users’ application code, which, if used with care, can help avoid the need for a separate application microcontroller in simple IoT device designs.

The eRIC devices are supported with development kits, which include two eRIC400 (400MHz) or eRIC900 (900MHz) RF transceiver modules with matching antennae, two development boards, batteries, USB leads, and a memory stick containing datasheets and software.

PC-based easyRadio Companion software and related drivers are available to interface with and control the development boards. Texas Instruments, which supplies the microcontroller in the eRIC modules, also offers its Code Composer Studio integrated development environment for advanced users who want to compile and load application software into the user partition of the modules’ flash memory.

The initial hype over the IoT is dying down now, as the hard work of developing devices and supporting infrastructure begins in earnest. With services such as Sigfox, standards such as easyRadio and LoRa, and modules from LPRS, it is becoming steadily easier to provide the ‘wireless wires’ necessary to ensure the connections necessary to turn ‘Things’ into parts of an ‘Internet of Things’.

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