Abstract: according to the requirements of secondary development interface in the engineering application of LED display screen, a method of secondary development interface is proposed, which is summarized into three types of interfaces: communication channel, program and command, and its basic functions are introduced. According to this scheme, the secondary development and system integration can be realized simply and quickly in engineering application.introduction
In the engineering application of LED display screen, there are single display screen projects, but more are multi display screen projects. For a single display screen, the control software configured by the manufacturer can meet the requirements directly; However, for multiple displays, especially for system integration projects, the control software configured by the manufacturer is difficult to meet the requirements. This is because, firstly, the control software configured by the manufacturer generally only realizes the general function, and it is difficult to meet the requirements for the personalized function. For example, the integration project needs to be connected with the background database to realize real-time information release, and it is difficult for the general control software to provide this function; Secondly, for the integration project, the display screen information release is only one part, which needs unified control and interface style; Thirdly, in a large integration project, many manufacturers may win the bid, or replace or add the products of other manufacturers after many years of project implementation, and the implementation technologies of different manufacturers may be different.
Therefore, in order to meet the application of LED display in engineering, manufacturers generally need to provide secondary development interfaces for system integrators to carry out secondary development and complete system integration. After market research, the secondary development interface of LED display screen is mixed, and there is no unified standard. Some are too simple to meet the engineering application, while others are too complex, resulting in long system integration cycle and high cost. Therefore, after research, this paper proposes a new design method of LED secondary development interface, which allows users to realize system integration simply and quickly, and reduce the time and cost of secondary development.
1. Main functional requirements analysis and model constructionIn engineering applications, LED display screen is mainly used to release information, especially to update information in real time according to the changes of background database.The typical application is the railway station, which updates the ticket information such as train number, soft / hard seat ticket, sleeper ticket and departure time in real time, as well as the information of arrival train number and delayed train number. In addition, there are temporary notices, train number changes, advertisements, waiting room locations, etc.
In the railway station integrated information management system, compared with the whole system, the information release of LED display screen is only one part, but the type, communication type and distribution position of LED display screen may be very complex, as shown in Figure 1. According to the size, hanging position, displayed content and function of the display screen, the display screen can be divided into general guidance information screen, waiting information screen, zoning screen, ticket check screen, channel display screen, platform screen and exit information screen. In terms of communication, serial port and network are generally used according to hardware conditions and location. The serial port is divided into RS485 and RS232. One RS485 is connected to multiple display screens, and one RS232 is connected to one display screen; The network is divided into wired network, wireless network and GPRS.
Figure 1 typical system integration diagram of LED display screenAfter comprehensive analysis, the functions of the display screen involved in the system include:(1) Release information, update information, advertising and guidance information; (2) Control display screen, such as restart, timing switch screen, setting parameters, etc; (3) Monitor the display screen to display the connection status, update time, etc.
Its working process is:(1) Connect the display screen; (2) Release information and download programs to the display screen; (3) Control and monitoring display screen; (4) Disconnect at the end of the operation.In fact, the function of system calling display screen is not complex, and the main difficulties are:
(1) How to realize the unification of multiple hardware connection modes, including serial port and network; (2) How to organize a variety of information display objects, including text, pictures, animation, clock, etc; (3) How to provide basic control commands according to the control requirements of LED display screen and adapt to a variety of system integration modes, including C / s, B / s, distributed and hierarchical control.In order to solve these difficulties and achieve the purpose of universal, simple and easy integration, after research, the LED secondary development interface model constructed in this paper is shown in Figure 2, and the main functions and processes are as follows:
(1) Call the communication control interface, create their communication channels according to different communication modes, and complete the connection of LED display screen; (2) Call the program production interface to create programs, add program objects, generate program data, and then use the command interface to send programs to the display screen to complete the information release; (3) Call the command interface to restart the display screen, turn on / off the screen, set the brightness, update time, read the display screen time, and complete the control and monitoring of the display screen; (4) When exiting the system, close the communication channel, release resources and end the call operation of the secondary development interface.