Welcome back to the world of Bluetooth. For those who may have missed them, in the first two articles of this series, I introduced the Bluetooth history and ecosystem ("No Blues with Bluetooth - Part 1," Circuit Cellar 405, April 2024) [1]. I then presented the overall Bluetooth protocol stack, differentiating Bluetooth "Classic" and Bluetooth low energy or BLE ("No Blues with Bluetooth - Part 2," Circuit Cellar 407, June 2024) [2]. In Part 3 I started to focus on BLE, and explained how a new device is discovered using the advertising mechanism ("No Blues with Bluetooth Part 3," Circuit Cellar 408, July 2024) [3].
This month, I will continue with a presentation of the connection-establishment phase between a peripheral (remote) and a central (controller) device. As you will discover, once connected, BLE allows a bidirectional communication flow between the two devices, and with very low power consumption on both sides.
As this is already my fourth article on this subject, you may start to ask yourself some questions. You would be right if you think that you can easily design a BLE project without actually knowing how it works. So, why am I writing all this stuff? Well, for three reasons. First, because understanding BLE internals allows you to use it at its best, and so to design far better devices. Second, because the design concepts of BLE may give you some nice ideas for your own developments, even if you don't plan to use Bluetooth at all. And third, because I think this is more than interesting! Bluetooth is indeed a nice piece of engineering, developed by talented engineers, and it is significantly more complex than it appears to the end user.
A last introductory word: This article, like the previous ones, presents BLE as originally specified in Bluetooth 4.0.
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