Replacing a protocol stack in Raspbian
This tutorial describes how to upgrade the Bluetooth protocol stack from version 5.43 to 5.50 on Raspbian Stretch. Bluetooth operation on the Pi has been less than stellar in reliability since it was first introduced in 2016, and this protocol stack upgrade resolved some of those issues. With the introduction of Raspbian Buster – done while this tutorial was being written – the Bluetooth protocol stack is now version 5.50. An upgrade to the operating system may now be the easier fix.
If you are faced with a existing Pi installation that has Bluetooth issues, but you’re unwilling to upgrade to the current release, this tutorial may offer you some insight into fixing your Bluetooth issues. Bear in mind that the protocol stack upgrade requires some effort and isn’t as smooth as what is offered in the latest Buster.
We’ll start this tutorial with Bluetooth theory. After identifying the Bluetooth protocol stack, we’ll see how to replace the current version with the latest version available from the Bluetooth development team. With the protocol stack installed, the tutorial reinforces what was covered in the theory, by using the command line to get a Bluetooth device working on the Pi.
Bluetooth in theory
Bluetooth was designed for devices that are in close proximity with one another to communicate. The Bluetooth protocol is a standard for radio frequency (RF) wireless operation in the congested 2.4GHz microwave frequency band.
The Bluetooth protocol uses 79 radio frequency channels of 1MHz to communicate, covering a frequency range of 2,402MHz to 2,480MHz. Bluetooth Low Energy (BLE), the standard designed for low power consumption, communicates using 40 2MHz channels.
Not all channels
