LED dot matrix displayComposition: it is a new type of display device, which is composed of multiple LED packages. In order to explain the principle of LED dot matrix display, a display system including hardware and software is designed and manufactured with single chip microcomputer as the control core.
　　
Introduction of the system hardware circuit of LED dot matrix display: the hardware circuit of the display controller is mainly composed of three parts: serial communication interface, expansion of external memory and LED dot matrix display drive and interface circuit. Generally speaking, there are many contents to be displayed, so the external data memory must be expanded. Static data memory has the advantages of low cost, low power consumption and fast reading and writing speed. We use two pieces of static ram62256 data memory (64KB in total). Store all the content codes to be displayed in 62256.
　　
Introduction of system software program of LED dot matrix display: software program is the core part of the whole control system. After the main program of the system starts, the system environment is initialized first, including setting serial port, timer, interrupt and port. The whole software design is mainly divided into two parts: display part and communication part.
　　
1. Display part: use the dynamic scanning method to realize the transmission control and display of Chinese characters, characters, images and data on the display screen. The program divides the data memory into three areas: display buffer, data storage area and receive buffer. The single chip microcomputer receives the data from the PC through the serial port interrupt, temporarily stores it in the receiving buffer for analysis and processing, saves it in the data storage area according to certain rules, and then extracts the data from the data in the memory according to the display mode sequence to display it in the display buffer. The display adopts progressive scanning. The real-time communication part of PC mainly uses the MCU serial port to interrupt the reception of data information and realize the data information transmission with the computer.
　　
2. Communication part: the upper computer software adopts visual basic programming, and uses VB to provide a powerful communication control MSComm, which controls the message format and protocol settings of serial port and serial port communication, and directly uses the serial port of PC to send data. In order to realize the reliable communication between single chip microcomputer and PC, both sides must have the same data format and baud rate. The software is relatively simple to use. When using, you can first use Microsoft Word to deal with the content to be displayed (note that the width of the page setting should be the same as that of the LED dot matrix display), then select the select all command and copy command in the edit menu, and then run the LED display Download Software v1.1. Select the "clipboard" button in the interface, and the content to be downloaded can be displayed in the preview box. After checking, select the baud rate and connect to the serial port, click the "download" button, and you can download the display. If you need to modify or display new content, repeat the above operations, which is very convenient to use.
　　
The circuit of LED dot matrix display can realize various display forms such as rolling up, moving up and moving left of any number of Chinese characters through key control. It can be widely used in airports, shopping malls, hospitals and other public places for text advertising, information release, etc. And it has the characteristics of small size, simple hardware circuit structure and easy implementation.