Bluetooth LE

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Bluetooth is one of these standards which have been around for so long that they finally work. These days, I’m using bluetooth mice, keyboards and speakers without any serious problem, but this took many years since the introduction of the standard, more than 20 years. In fact the company that introduced Bluetooth, Ericsson, stopped producing mobile phones.

The protocol has seen many revisions, of course, but version 4 included an interesting addition: low energy (LE) devices. The notion of low energy is of course relative – the key point here is that Bluetooth LE devices use less energy that classical Bluetooth ones. The general idea is that they can run a few months on a small lithium battery.

There was a lot of noise when Apple introduced which is a standard for building beacons, i.e. Bluetooth LE devices that simply broadcast their identity. In turn, Google introduced Eddystone, an open specification for beacons, so I assumed that Bluetooth LE was about these beacons. I was wrong.

Turns out a lot of devices use Bluetooth LE. My iPhone connects to my Fitbit Charge using bluetooth LE, in turn the iPhone implements a Bluetooth LE profile and reports its battery level and local time, two bits of information that could be read by my laptop. The cadence measuring device I added to my bike? Bluetooth LE, with a standard profile! That was a good surprise and me realise there are many profiles for sport and medical sensors.

The Bluetooth explorer provided by Apple with the Hardware development tool supports Bluetooth LE. Turning it on revealed a few devices besides my phone and my watch in my close neighbourhood: an Apple TV and a Samsung TV, both advertising over Bluetooth LE. I found a pretty good introduction to Bluetooth LE on Github. While classical Bluetooth is connection based, Bluetooth LE is based on read/write/notify operations, closer to low-level protocols like SNMP or I²C.

While there is a lot of attention on the beacon use case, Bluetooth LE has the potential to integrate a lot of electronic devices: sensors, but also things who needs some for of setup or configuration: clocks, washing machines, ovens, etc. Currently the focus seems to be on sport and health equipment, but I could see move this to food and cleaning appliances. Only time will tell…

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