I. Internet of Things Network Architecture
The IoT networking uses a layered communication system architecture, including a perceptual extension system, a transmission system, a business operations management system, and various applications, supporting different communication protocols at different levels, as shown in Figure 1. The perceptual extension system includes sensing and control technologies, consisting of perceptual extension layer devices and gateways, and supports multiple perceptual extension networks including communication protocols such as Lonworks, UPnP, and Zigbee. The sensing device can connect to the core network through multiple access technologies to realize remote transmission of data. The business operations management system is oriented to energy-consuming facilities within the Internet of Things, including application systems and business management support systems. The application system provides end users with metrology statistics, remote measurement and control, intelligent linkage, and other extended types of services. The business management support system implements functions such as user management, security, authentication, authorization, and accounting.
Second, the Internet of Things gateway concept
As the link between the connection sensing layer and the network layer, the IoT gateway can realize the protocol conversion between the sensing network and the communication network, and between different types of sensing networks. Can achieve wide area interconnection. Local area interconnection can also be implemented. In the wireless sensor network, the IoT gateway is an indispensable core device. In addition, the IoT gateway needs to have the device management function. The operator can manage the underlying sensing nodes through the IoT gateway device, understand the related information of each node, and realize remote control.
From the definition of IoT gateway, the IoT gateway is difficult to appear in a relatively fixed form. Generally speaking, any device that can transmit information collected by the sensing layer to the Internet through the protocol conversion of the terminal can be regarded as an IoT gateway. The shape can be a box shape or a tablet computer, and can have an interactive form of a display screen, or a closed or semi-closed non-interactive form.
Third, the key technology of the Internet of Things gateway
1. Multi-standard interworking access capability: There are many technical standards currently used for short-range communication. Common sensor network technologies include ZigBee, Z-Wave, RUBEE, WirelessHART, IETF6IowPAN, AM'/ANrr+, Wibree,]nSTeON, and others. Various technologies are mainly developed for a certain type of application, and there is a lack of compatibility and system planning. For example, Z.Wave is mainly used in wireless intelligent home networks, RUBEE is suitable for harsh environments, and WirelessHART is mainly concentrated in industrial monitoring. Realizing the interconnection and intercommunication of various communication technology standards has become a problem that the Internet of Things gateway must solve. A separate gateway is designed for each standard, and then implemented through a unified interface between the gateways. Or use the standard adaptation layer, different technical standards to develop the corresponding interface implementation.
2. Manageability of the gateway: The IoT gateway acts as a network element connected to the network, and must have certain management functions, including registration login management, rights management, task management, data management, fault management, status monitoring, and remote diagnosis. , parameter query and configuration, event processing, remote control, remote upgrade, etc. If you need to implement the management of the entire network, you must not only manage the gateway device itself, but also implement the management of each node in the subnet through the gateway, such as obtaining the identity, status, attributes, etc. of the node, as well as remote wake-up, control, and Diagnosis, upgrade maintenance, etc. Although different according to the technical standards of the subnet. The complexity of the protocol is different, and the management content that can be performed is quite different.
Fourth, the Internet of Things gateway design method
When designing the IoT intelligent gateway application system, the following general design methods can be used as a guide.
1. Determine system functionality and performance. The design goal of the IoT intelligent gateway application system is determined by the demand survey, which includes system functions and performance. System functions mainly include data acquisition, data processing, and output control.
2. Determine the basic structure of the system. The application structure of the IoT intelligent gateway is generally in the form of a microcontroller externally extending the relevant circuit. Determine the microcontroller, memory allocation and input/output mode in the system to determine the basic composition of the IoT intelligent gateway application system.
(1) Single chip microcomputer. When designing the system in detail, first determine the model of the microcontroller. The model of the selected MCU is different, and the system structure is different.
(2) Memory allocation. Different microcontrollers have different memory organizations. The allocation of memory should be reasonable according to the needs of the application system.
(3) I/O mode. Different input/output modes have a direct impact on the software and hardware structure of the microcontroller application system. In the MCU application system, the commonly used I/O modes mainly include: unconditional transmission mode (synchronous transmission mode), inquiry mode, and interrupt mode.
(4) Network controller. The network controller with stable performance, simple structure and easy programming can play a key role in optimizing the application system of the IoT intelligent gateway.
The working modes of the IoT intelligent gateway application system can be divided into two categories, server and client. Regardless of the mode of operation, network parameters need to be configured for the Ethernet controller to achieve the most basic physical connection (ie, pingable).
3. Hardware design. The hardware design of the IoT intelligent gateway application system is developed around the expansion of external functions of the MCU and the network controller. The basic structure is shown in the figure.
(1) Program memory. In the conventional single-chip microcomputer, there is no on-chip program memory or the storage capacity is not large enough, and the program memory needs to be externally expanded. Externally extended memory is usually FLASH memory. Today's microcontrollers generally integrate a large amount of program memory, which does not require program memory expansion.
(2) Data memory. The data memory is used to temporarily save intermediate results in the running of the program, usually consisting of RAM. Most microcontrollers provide a small amount of on-chip data memory that extends the external data memory only when the on-chip data memory is not sufficient. Whether it is program memory or data memory, the design principle of the memory is to reduce the number of memory chips as much as possible while the storage capacity can meet the requirements.
(3) I/O interface. Due to the variety of peripherals, the interface circuits between the microcontroller and peripherals are also different. Therefore, the I/O interface is often one of the most complex and difficult parts of the microcontroller application system.
(4) Decoding circuit. When an external expansion circuit is required, it is often necessary to design a decoding circuit. The decoding circuit should be as simple as possible, requiring a reasonable allocation of memory space, and the decoding method is properly selected.
4. Software design. Software is an important part of the IoT intelligent gateway application system. The software of the general computer application system includes system software and user software, while the software in the IoT intelligent gateway application system generally only has user software, that is, application system software. The key to software design is to determine the tasks that the software should perform and select the appropriate software structure.
(1) Task determination. According to the division of functions of the system software and hardware, determine what functions the software should complete. As the software that implements the control function, the control object, control signal, and control timing should be clearly defined; as the software that implements the processing function, it should be clear what the input is, what kind of processing (ie, processing algorithm), and what kind of output is generated.
(2) Software structure. Software architecture is closely related to programming techniques. Programming techniques provide a basic approach to programming, and the most common programming method is modular programming. Modular programming has the characteristics of clear structure, clear function, simple design, program modules can be shared, easy to expand functions and easy to maintain. In order to program the module, the software function is first divided into several sub-function modules, and then the input, output and mutual connection of each module are determined.
Want to know more about IoT communication technology design information, please pay attention to the topic of "Internet of Things Core Communication"
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