How does Bluetooth protocol stack work?

What’s protocol stack?

The Bluetooth protocol is a kind of communication protocol. Generally, we call the implementation code of a certain protocol as protocol stack. The BLE protocol stack is the code that implements the Bluetooth Low Energy protocol.

Bluetooth protocol include Basic Rate/Enhanced Data Rate (BR/EDR) and Low Energy (LE) .

How many solutions for Bluetooth protocol stack ?

1. Host+controller dual-chip standard architecture

Bluetooth SIG standards allows mobile phone manufacturers, such as Apple, to replace the old AP (Access Protocol) with a new AP without any changes to the Bluetooth module; similarly, replacing the old Bluetooth module with a new Bluetooth module, AP side also don’t need make any changes. This standard divides the Bluetooth protocol stack into two parts: the host and the controller. The host runs on the AP and the controller runs on the Bluetooth module. The two communicate through the HCI protocol, so we call it the dual-chip standard solution.

2. Single chip control entire bluetooth protocol stack

Mobile phone bluetooth accessories are another common application. Generally, the functions of mobile phone accessories are relatively simple, normally they need low lost. It is a good choice to use a chip to implement the entire Bluetooth protocol stack. All functions are placed on one chip, that is, the host and controller are on the same chip. There is no need for physical HCI to exist. Directly interact with each other through API.

3. Custom dual chip architecture

The functional requirements of some Bluetooth devices are complicated. It requires a very powerful MCU as the master application, and the Bluetooth SoC is only a part of the entire system. In this case, most of the Bluetooth protocol stack functions or the entire Bluetooth protocol stack functions are running in the Bluetooth SoC, the Bluetooth application runs in the main MCU. The communication protocol between the master MCU and the Bluetooth SoC is defined by the manufacturer, so it is called a custom dual-chip architecture Bluetooth solution. This kind of scheme is also very common. The HCI interface is used for communication between the main MCU and the Bluetooth SoC. The HCI here is only used for physical communication. The main body of communication is not the host and controller. The communication data package does not follow the Bluetooth SIG standard.

Feasycom’s BT825B, BT805B, BW121 are bluetooth protocol stack module, support customer write firmware on their MCU directly, the cost would be cheaper than normal products. If you have interests to learn details, please feel free to contact with Feasycom sales team.