How to turn a home thermostat into a smart device: easing the connectivity challenge

May 09, 2017 // By Vikram Ramanna
Consumers are developing a taste for smart home devices, thanks in part to the new sophistication of voice-controlled technologies such as Apple’s Siri Remote and the Alexa Voice Service on Amazon Echo, and of systems for the remote control of home devices such as Google’s Nest products.

This means that many manufacturers of control devices such as thermostats are now embracing the challenge of turning a conventional ‘dumb’ product into a smart, connected product (see figure 1). Adding connectivity entails the use of a standard RF technology such as Wi-Fi or Bluetooth Low Energy communication. Of course, embedded device designers have no shortage of Wi-Fi and Bluetooth transceivers or modules to choose from, supplied by a wide range of semiconductor vendors. RF IC manufacturers also provide ready-made and free communications protocol stacks for Wi-Fi, Bluetooth and internet connectivity.

And if a thermostat design needs to be made ‘smarter’, microcontroller manufacturers always provide a migration path to upgrade the processing power, addressable memory and peripheral feature set of an existing thermostat’s MCU.

From a purely hardware point of view, then, the modification of an existing design to become a smart, connected product appears to be readily supported by a vibrant commercial off-the-shelf IC market. The real question for the embedded developer, however, is over the best way to combine the hardware, firmware and application software necessary to meet user expectations for functionality, and to provide for interoperability with platforms such as Apple’s HomeKit or Google’s Works with Nest technologies. In reality, there is a great deal more to the realization of a successful smart thermostat design than wireless connectivity: the development of software will occupy the biggest part of the design team’s time.

Figure 1: next-generation home thermostats will support multiple one- and two-way communications interfaces.

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