Design Principle of Bluetooth protocol stack

We have already learned about the principles and circuits of the Bluetooth protocol stack. Now we will introduce the SoC Structure Design for the embedded Bluetooth protocol stack. According to the hardware structure of the above Bluetooth protocol stack, we can see that if we use the SoC structure to design the Bluetooth protocol stack, We can embed the Bluetooth communication module and open the internal CPU to users.

When designing the SoC structure embedded in the Bluetooth protocol, consider the following issues.

① Data processing capability and speed. data processing capabilities are mainly reflected in two aspects: one is the size of data buffer memory, and the other is the degree of support for data processing algorithms. data processing speed is an important issue. the data processing speed is not only related to the system clock frequency, but also directly related to the CPU and internal bus structure.

② Relationship between communication operations and System Operation. embedded in the Bluetooth communication stack SoC, communication is a function of the system. SoC also needs to implement other functions of the system. due to the serial structure of the CPU, when the system needs to enable both the communication function and other important functions (such as the implementation of system data collection operations), it is necessary to use appropriate methods for coordination. in fact, this is the real-time problem of the embedded Bluetooth SoC device system.

③ Device power loss. power loss is an important issue in SoC design. in addition to using the corresponding technology to achieve the lowest power loss, the system power loss must also be reduced through the system structure design. low-Power Design is essential for systems with special requirements for power loss.

According to the above three requirements, in the embedded Bluetooth SoC, if the data processing volume is large, the data processing speed should be considered. the user's system CPU is a serial mode of work. Therefore, in the process of large data volume communication, how to complete other system functions is an important aspect of SoC structure design. for example, when using Bluetooth Technology to transmit images, the communication system must keep working continuously, and a large number of Flash memory needs to be designed in SoC. since the transmitted images must be compressed and decompressed, full coordination is required between communication continuity and image compression/decompression, and hardware parallel processing technology is used. in this case, the CPU is just an operational controller device used to start or stop an operation. we can see that the SoC structure should be designed for different types of applications.

The basic functions of smart sensors are as follows.

① Signal conversion. This part of the circuit is used to convert the corresponding physical quantity into a voltage signal, and then enlarge and filter it. The processing result is used as the input signal of the data collection circuit.

② Data collection. The data collection circuit function is to convert the analog signal output from the signal conversion circuit to a digital signal (data sequence), and then output the digital signal to the CPU for corresponding processing.

③ Data processing. data processing functions of smart sensors are generally not uniform. generally, digital filtering is required. some smart sensors also need to process other signals, such as signal amplitude discrimination, signal feature extraction, and display processing. in short, data processing requirements vary in different application fields.

④ Data transmission. in the control system, intelligent sensors collect and organize data, and need to transmit the data to the system core controller or other control units. due to the characteristics of the control system, data transmission usually requires a certain space distance. Therefore, special circuits and methods are required for data transmission. for example, after encoding the data, the current loop or RS232 is used for transmission. in most cases, wired transmission is used to connect sensors and control systems in existing control systems.

For smart sensors, the amount of data transmitted is generally not very large (such as pressure and temperature sensors). Therefore, to meet the needs of smart sensors, embedded Bluetooth SoC devices do not require a large storage capacity; however, you must consider the storage space required for implementing the Bluetooth protocol. the Bluetooth protocol stack Processing Software occupies a large amount of memory, so it must be simplified. to ensure the security and reliability of the control system, we also need to consider using the user protocol instead of the processing protocol defined by bluetooth.

From the above analysis, we can conclude that:

① The data transmission volume of smart sensors is relatively small and does not require compression or encoding. It can be set to 1 kb or less.

② To ensure the security and reliability of the control system, the upper-layer processing protocol must be changed to the user-layer protocol, which is compiled by the user.

In order to design a smart sensor embedded Bluetooth SoC structure, the Bluetooth protocol stack is simplified, and only Core protocols and alternative cable protocols in the Bluetooth protocol are used. in SoC, the Bluetooth protocol stack consists of software and hardware. core protocols are implemented by hardware, while Link Management and other components are implemented by software. all relevant protocol software is stored in the ROM, which can be called directly when the user uses the communication stack. it should be pointed out that the communication stack is designed as a whole, so the call must also be called as a whole. in other words, the communication stack is called as a complete subroutine module.