Design of remote control system for residential area based on CMX869BE2 modulation and demodulation chip and 89X51 series single chip microcomputer
Ora pubblicata: 2020-05-11 12:00:56
With the rapid development of society, the automation of various control devices in the industrial field is getting higher and higher, and the scope of use is becoming wider and wider. This has made many automation-related technologies penetrate into the daily lives of ordinary people. The remote operation of the equipment will greatly improve work efficiency and reduce labor costs. Therefore, the demand for various networks is increasing. As we all know, when constructing a cell remote control network, there are two implementation schemes: when the terminal is close to the distance, Ethernet transmission is used; when the distance is far away, the fiber or modem transmission is used. Due to the use of Ethernet and optical fiber transmission in the line relay and laying costs, as well as the higher requirements for existing electrical equipment, the remote control of the cell is not too large and the real-time demand is high. Ethernet and optical fiber transmission Not the optimal solution. Using a modulation and demodulation scheme, it is very complicated to start development from the underlying protocol stack of the modem. When a dedicated network is built using a relatively general-purpose modem product on the market, it will increase the complexity of the network, and No user programming interface is provided, which causes unnecessary trouble for centralized management and maintenance. This article will introduce a solution for the remote control network of a cell between the above two schemes. It has a complete and stable V.32bis protocol stack, which is a low-cost, high-performance, easy to develop, and adaptable control implementation scheme. .
1. Hardware design scheme based on high-performance modem chip CMX869BE2
This solution uses CML869's CMX869 modem chip as the core device. Its main features are:
Fast transmission speed Ordinary modem chip can also be used for network control, but its modulation method and transmission speed limit the scope of use. CMX869 adopts C-Bus serial bus and full-duplex QAM (quadrature amplitude modulation) modulation method, and is backward compatible with FSK (frequency shift keying). The serial bus clock frequency can be up to 5 MHz and the modulation transmission rate can be up to 28.8 Kb / s.
Good transmission performance Compatible with program-controlled switching network, providing 2/4 line transmission interface with echo cancellation, the signal strength of the sending circuit is 0.5 dBm, and the receiving sensitivity of the receiving circuit can reach -30 dBm. Following the situation, the transmission distance is greater than 4 km. At the same time, it can automatically detect the line quality and adjust it in real time, which is suitable for long-distance transmission.
Rich resources Through C-BUS serial bus can access multiple commands and status can read and write register resources, and provides a complete and stable V.32bis protocol stack, easy to call.
Low power consumption adopts 3.3 V low-voltage working mode, which can automatically interrupt the established idle connection through programming, consumes very low current when in power-saving working mode, and can automatically return to normal working mode when the serial port receives data, with options The establishment of the connection is suitable for applications requiring low power consumption. Good environmental adaptability The storage temperature of CMX869 is between -55 ～ + 125 ℃ and the operating temperature is between -40 ～ + 85 ℃, which is suitable for outdoor work in severe cold and hot environment.
2. Software implementation process
Another feature of this solution is that the software development is simple, because CMX869 provides a wealth of command and status readable and writable register resources, as well as a perfect and stable V.32bis protocol stack. Assembly language or C language programming, by calling the constructed function to set and read and write each register, you can complete the control of the CMX869 state and send and receive data, shortening the software development and debugging cycle.
Because CMX869 functions and protocol packaging are relatively independent, developers only need to be familiar with the reading and writing of their specific registers and the CX51 programming of the single-chip computer to implement network interconnection. The software of this solution mainly includes the management terminal software and remote control software. It realizes that the service query command is sent to the CMX869 interface from the serial port of the management terminal control unit. After the modulation and demodulation, the data is forwarded to the serial port of the remote control unit. The terminal control unit transmits the collected data back to the serial port of the management terminal control unit through the original path. The baud rate used by the serial port is 115.2 Kb / s, and the transmission protocol is V.32bis.
The CMX869 modulation and demodulation module designed based on this scheme has been used in engineering, and its excellent data transmission and control performance has been verified, and it can adapt to the harsh environment of industrial use. This solution is simple to implement and is suitable for applications with low cost requirements, harsh weather conditions, remote unattended, low transmission data volume and high real-time performance, such as security system dedicated line, remote control management, remote instrument reading, Environmental meteorological data collection, POS terminal, telephone line data transmission, home security, etc.