Adding Bluetooth connectivity to your IoT design

We have the current trend of the Internet of Things (IoT) to thank for driving a surge of embedded system development.

We have the current trend of the Internet of Things (IoT) to thank for driving a surge of embedded system development. As more and more B2B and B2C organisations strive to cloud-enable their products and develop a new range of services offering connectivity either direct to the cloud or via a gateway is a vital element of any design. 

While wired connectivity is possible, and for some applications highly desirable, the majority of IoT-based developments will need to connect wirelessly to the Internet. 
Some IoT architectures feature a gateway platform to provide a degree of local storage, intelligence within the local node network and longer-range communication to the cloud. 

Typically Wi-Fi is used for the long-range communication while Bluetooth is emerging as the protocol of choice for the edge nodes such as sensors, switches and appliances. Typically designers have had to grapple with designing a wireless capability into their embedded design, something that is as complex as the embedded compute requirements themselves. 

Bluetooth has been around for many years, the latest major revision of this 2.4 GHz radio protocol being in 2010 when the core specification of Bluetooth 4.0 was introduced. 

This is also called Bluetooth Smart. It was in this release that the Bluetooth Low Energy (BLE) protocol was made public. BLE uses a completely different protocol stack from the Classic Bluetooth specifications (v1.0 – v3.0) and is aimed at very low power applications that typically may operate off a single cell battery. 

The last couple of years have seen several sub version enhancements added to the core BLE specification, now 4.2, that incorporates more efficient bulk data transfers and more communications flexibility specifically for IoT designs, to name a few.

Optimised for low power consumption rather than higher data rates BLE is ideally suited for use with battery powered sensors that need to transfer relatively small amounts of data. It achieves this low power profile by limiting the time that the radio transceiver is in use, scanning few advertising (the term used for part of the process to initiate a link) channels and only wakes to send or receive small packets of data. 
The BLE protocol also facilitates a very rapid approach to setting up link connections.

The flip side to BLE’s low power consumption, typically a hundredth of that when using a Classic Bluetooth connection, is that the maximum short burst data rate of BLE is 100 kbps compared to Classic Bluetooth’s constant streaming capability with a maximum rate of up to 3 Mbps (Bluetooth v2.0 + Enhanced Data Rate).

Clearly, use of the Bluetooth v4.x BLE protocol is ideal for IoT-based sensor and control applications. Should data volumes dictate the requirement for higher transfer rates then the use of a Classic

Bluetooth protocol is recommended, although there is an impact on the required power budget.
Whichever Bluetooth profile suits your application it will be down to the embedded developer to integrate such connectivity together with the host processing. 

Designing your own discrete wireless transceiver might well be a tempting thought, but don’t forget the amount of time the design, prototyping and testing will take. And if that isn’t enough you have to have the design certified for use across the many regions and countries your product might end up in. The alternative is to select a pre-certified Bluetooth module that you can easily integrate into your design. 

Whichever approach you use, pre-certified wireless modules provide a very quick and inexpensive way of incorporating Bluetooth connectivity to your design. In this way you can balance the commercial aspects of time to market with on-target bill of material costs.

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