Smart Home Bus System Topics: Overview of Mainstream Bus System Features
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Smart home bus system basics
After more than ten years of development in the domestic market, smart homes have gradually matured through convergence in technology and integration. The main characteristic of the bus technology is that all equipment communication and control are based on a bus. It is a fully distributed intelligent control network technology. Its product modules have two-way communication capabilities, as well as interoperability and interchangeability, and its control components can be programmed. . The influential bus technologies in the market include RS-485, KNX, CAN, C-Bus, SCS-BUS, Lon Works, and Modbus. Bus technology products are more suitable for the control of large areas such as building intelligence and community intelligence. Its advantages lie in mature technology, stable system, high reliability, and wide application.
Mainstream bus system features overview
RS-485 Bus RS-485 is a very common bus. The RS-485 serial bus standard is widely used when the communication distance is several tens of meters to 1000 meters. It uses balanced transmission and differential reception, so it has the ability to suppress common-mode interference. In addition to the bus transceiver's high sensitivity, it can detect voltages as low as 200mV, so the transmitted signal can be recovered beyond a few kilometers.
The general RS-485 in the market adopts a half-duplex working mode, and only one point can be in a sending state at any time. Therefore, the transmission circuit must be controlled by the enable signal. RS-485 is very convenient for multi-point interconnections, eliminating many signal lines. Application of RS-485 can be networked to form a distributed system that allows up to 32 drives in parallel and 32 receivers.
System features:
From the perspective of the development of intelligent lighting, the earliest products generally adopt the RS485 technology, which is a serial communication standard. Because only the electrical connection specification of the physical layer is specified, each company defines its own product communication protocol. RS485 products are many, but they cannot communicate directly with each other. RS485 generally needs a main contact point. The communication mode adopts the polling mode. The modules use the “hand-in-hand†connection mode. Therefore, the communication speed is not high (general 9.6 Kbps), and the number of modules is limited.
KNX bus KNX is the abbreviation for Konnex. In May 1999, the European three major bus protocols EIB, BatiBus and EHSA merged to form the Konnex Association and proposed the KNX protocol. The agreement is based on the EIB, taking into account the physical layer specifications of BatiBus and EHSA, and absorbing the advantages of configuration modes such as BatiBus and EHSA, providing a complete solution for home and building automation.
KNX is the only global residential and building control standard. In the KNX system, the bus connection method is that the area bus is connected to the trunk line, and the trunk line is connected to the bus line. The system allows 15 areas, that is, 15 area buses, and each area bus or trunk line allows connection of up to 15 buses. , and each bus allows up to 64 devices, depending on the power supply and device power consumption. Each regional bus, main line or bus requires a transformer to supply power, and each bus is separated by an isolator. In the entire system, all sensors are connected to the brake via data lines, and the brakes control the electrical appliances by controlling the power circuit. All devices communicate data via the same bus. Sensors send command data and the corresponding address brakes perform the appropriate functions.
In addition, the entire system can also achieve corresponding system functions by setting control parameters in advance, such as group commands, logic sequence, and control adjustment tasks. At the same time, all signals are propagated on the bus in the form of serial asynchronous transmissions. That is to say, at any time, all bus devices always receive information on the bus at the same time, as long as the bus no longer transmits information. The device can independently decide to send the message to the bus. KNX has three structures: linear, tree, and star.
System features:
KNX can be used in the latest buildings as well as existing buildings and can be used for all possible functions/applications in residential and building control, including: lighting, close control of multiple safety systems, heating, ventilation, air conditioning , monitoring, alarm, water control, energy management, measurement and household appliances, audio and many other fields. In addition, KNX is more comfortable and safer, and it has made significant contributions to energy conservation and climate protection, but the cost of the KNX bus is high. It is worth mentioning that KNX technology was approved as the Chinese standard GB/Z20965 in 2007.
Long Works
Long Works Bus was launched by Echelon Corporation in the United States and jointly promoted by Motorola and Toshiba. It uses the full 7-layer communication protocol of the ISO/OSI model and uses an object-oriented design method to simplify network communication design to parameter settings through network variables. Supports various communication media such as twisted pair, coaxial cable, optical fiber cable, and infrared ray. The communication speed ranges from 300bit/s to 1.5M/s, and the direct communication distance is up to 2700m (78Kbit/s). It is known as the universal control network. . By 2010, 90 million devices had used LonWorks network technology.
System features:
The LonTalk protocol adopted by the Lon Works bus technology is encapsulated into Neuron neuron chips and implemented. In the field of smart home, its biggest feature is that unlike other smart home bus systems, there must be a brain-like host. Lon Works bus technology does not require a host, it uses a neural network. Each node is a neuron. When these neurons connect together, they can work together and do not need another brain to control. Therefore, security and stability are greatly improved over other buses. Lon Works lacks the real-time nature and ability to process large amounts of data. Second, because Lon Works relies on Echelon's Neuron chip, its full openness has also been questioned.
CAN Bus The beginning of the CAN bus is a multi-master local network launched by Germany's BOSCH company in 1983 for leading automotive applications. It belongs to the category of Fieldbus and has advantages such as high performance, high reliability, and real-time performance. It is now widely used in smart home systems. In November 1993, ISO formally issued the Controller Area Network CAN international standard, paving the way for the standardization and standardization of controller LANs. One of the greatest features of the CAN bus protocol is the abolition of the conventional station address coding and instead of coding the communication data block.
The advantage of this method is that the number of nodes in the network is theoretically unlimited, and the identification code of the data block can be composed of 11-bit or 29-bit binary numbers, so that 2 or more different data blocks can be defined. This method of encoding data blocks also enables different nodes to receive the same data at the same time, which is very useful in distributed control systems.
The length of the data segment is up to 8 bytes, which can meet the general requirements of control commands, working status and test data in the general industry. At the same time, 8 bytes do not occupy the bus for too long, thus ensuring the real-time communication.
System features:
The CAN bus protocol adopts CRC inspection and can provide corresponding error processing functions, ensuring the reliability of data communication. The excellent features, high reliability, and unique design of the CAN bus have been increasingly taken seriously by all walks of life. One of the most promising buses. The CAN bus has the same defects as the 485. It cannot connect to the tree bus. The signal line should be connected like a cable TV. It is often used as a branch connection of a large system.
The C-Bus C-BUS system was developed by Clipsal Australia. C-BUS is an intelligent control system that uses unshielded twisted pair as a bus carrier and is widely used in the integrated control and integrated energy management of lighting, air conditioning, fire detection, entrance and exit, and security systems in buildings. The core of the C-BUS control system is the main controller and the bus connector. The main controller stores the control program, realizes the communication between the modules and the communication with the programming computer, and collects the input unit information through the control bus, according to the pre-programmed The program controls all output modules; its RS-232 standard interface is used to connect with the programming computer, and is programmed and monitored on the computer through dedicated software. After the programming is completed and downloaded to the main controller, the computer is only monitored, ie C- The operation of the BUS does not require any computer intervention.
The C-BUS control system uses the human environment as the main service object and provides various ways of receiving external instructions, such as control buttons, optical sensors, passive infrared detectors, and timing units. Actually, C-BUS is a typical system-based control product based on computer bus control technology for intelligent building demand. The arbitrary combination of modules makes the system design very flexible and convenient. The control button for C-BUS products for home use is one, two, and four buttons. The installation method is the same as the commonly used concealed lamp switch. Each button can be programmed to control one or more loads. It can be used for important places. Multiple buttons enable lighting scene control to adapt to the different requirements of different work on the lighting system.
System features:
C-BUS is a very flexible flexible control system. This is because all input and output components are self-contained with microprocessors and interconnected via a bus. External event information comes from the input components, passes through the bus to the corresponding output components and is pre-programmed. The program controls the connected load. Each component can be programmed on demand to suit any application. Its flexible programming makes it very easy to adjust the control program without changing any hardware wiring. As the administrator of the system, it is better to master the programming skills so that it can adapt to changes in the use requirements in time.
SCS-BUS Bus SCS-BUS refers to the structured cabling/bus system. It is an independent, self-contained dual-bus system developed by BTICINO. With stable performance and high speed of response, it can meet various smart home function requirements. The function is also the most complete in the industry. , is a dominant building automation (BA) and home automation (HA) standard in Europe.
The SCS-BUS communication protocol follows the OSI Open System Interconnection Reference Model and provides all seven layers of services defined by the OSI model. This is one of its advanced features. The physical layer and the link layer obviously depend on the characteristics of the physical medium. SCS-BUS specifies carrier sense multiple access (CSMA) with collision detection to optimize the media interface by optimizing anti-collision; the network layer controls information through the network protocol. (NPCI) control jumps; the logic relationship of the transport layer includes one-to-many connectionless or multi-endpoint transmission, one pair of all connectionless broadcasting, one-to-one connectionless, one-to-one steering connection, which provides addresses and The abstract internal expressions map communication access identifiers, etc.; through the reserved session and presentation layers, all devices are clearly mapped out; the application layer uses the API (Application Programming Interface) functions of the SCS-BUS network user/server management. The layer assigns the communication access identifier to the communication group internal request, or the shared variable, to complete the receive (one-to-many) and send (one-to-one) function.
System features:
The SCS-BUS communication protocol supports a combination of communication medium segmented networks, including twisted pair, transmission lines, and wireless frequency transmission. The cost of SCS-BUS twisted pair free topology is low. The bit-level collision detection of control logic 0 improves the reliability of transmission. The physical length of each pair of rough twisted wires can be up to 2,000 meters. The SCS transmission line uses a new type of extended frequency modulation technology. Through the corresponding number of matching filters, the integrity and reliability of the transmission line group address transmission are guaranteed.
Modbus ModBus was invented by Schneider Electric's Modicon brand in 1979 and is the world's first bus protocol for industrial use. In order to better popularize and promote the distributed application of Mod Bus on Ethernet, Schneider has transferred the ownership of the Mod Bus protocol to the IDA (Interface for Distributed Automation) organization and established ModBus-IDA. The organization laid the foundation for the future development of ModBus.
The Mod Bus protocol is a common language used in electronic controllers. Through this protocol, controllers can communicate with each other or via a network, such as Ethernet and other devices, which has become a common industry standard. With it, the control equipment produced by different manufacturers can be connected into an industrial network for centralized monitoring. This protocol defines a message structure that can be used by a controller regardless of the network through which it communicates. It describes how the controller requests access to other devices, how to respond to requests from other devices, and how to detect and record errors. It has developed a common format for message domain patterns and content. When communicating over a Mod bus network, this protocol determines that each controller needs to know their device address, identify messages sent by address, and decide what action to take. If you need to respond, the controller will generate feedback and send it using the Mod Bus protocol. On other networks, messages containing the Mod Bus protocol are converted into frames or packet structures used on this network. This conversion also extends the method of addressing section addresses, routing paths, and error detection based on specific networks.
System features:
Standard, open, users can use the Modbus protocol free of charge and with confidence, do not need to pay licensing fees, and will not infringe intellectual property rights. At present, there are more than 400 manufacturers that support Modbus and more than 600 products that support Modbus. Modbus can support a variety of electrical interfaces, such as RS-232, RS-485, etc., and can also be transmitted on various media, such as twisted pair, optical fiber, and wireless. The Modbus frame format is simple, compact and easy to understand. Users are easy to use, and vendor development is simple.