The asynchronous graphic control technology of LED electronic display means that the LED screen has the ability of storage and automatic playback. The edited text and non-gray-scale pictures on the PC are transmitted to the LED screen through the serial port or other network interface, and then the LED screen is offline. Automatic playback, generally does not have the ability to display multiple grayscales, mainly used to display text and simple graphic information, and can be connected to multiple screens. The main control PC transmits the information to be displayed and various control commands to the control board in the screen through serial communication. The control board in the screen contains a single-chip microcomputer and memory. The control board in the screen stores the information, and then displays it in accordance with the command. On the screen.
(1) Main features of asynchronous system
1. Due to the limitation of content storage space, most of the displayed content is mainly text, pictures, and characters.
2. Because the principle of the asynchronous system is to store the content to be displayed in the control system in advance, so as to avoid occupying the control computer. Can save costs.
3. It is mostly used for display screens with a small area that do not need to be changed frequently.
(2) Points for Attention in Asynchronous Graphic and Text Control Technology
1. Adapter: The host computer uses the serial port RS232 protocol to go online through the RS232-RS485 adapter, which is an optical isolation type.
2. Control panel: Receive the information to be displayed and various control commands transmitted by the PC through serial communication. The control panel contains a single-chip microcomputer and memory. The control panel in the screen stores the information, and then displays it on the screen according to the command. Features are as follows:
1. When the vertical dots are within 128, the horizontal dots can be up to 2000 dots. If the vertical is 16 points, the horizontal can reach 4000 points.
2. The large-capacity memory supports the first- and second-level Chinese fonts and a large number of proprietary fonts, and the storage capacity is 16 scenes.
3. It can be controlled by computer or displayed offline.
4. The information can be stored for 1 year after power failure.
5. With perpetual calendar real-time clock function.
(three) single network cable (four cores)
Using a four-wire system: a pair of differential twisted-pair wires receive, and the other pair of differential twisted-pair wires send. The communication distance is 1200 meters. It adopts a bus-type networking structure, with a maximum of 32 lower-level computers.
(four) host computer editing and broadcasting software
Communication screen LED program editing software, in line with LED graphic screen control protocol. It is suitable for editing and broadcasting text and image programs of multiple monochromatic or dual-primary color LED display screens of different lengths and different widths. Send 16 more programs each time.
(5) LED graphic screen control protocol
1. This protocol supports dot-matrix single-color, dual-color, graphic and text networked LED displays.
2. The networking form is bus type, the upper computer is a PC computer, and the lower computer is the single-chip microcomputer in the LED display control board. It adopts four-wire system, and the online protocol is RS485.
3. The host computer adopts the serial port RS232 protocol to go online through the adapter conversion.
4. Support TCP/IP protocol transmission.
Asynchronous system is mainly applied to the display screen with a small area and does not require the display content to be displayed synchronously with the control computer. Such as the dynamic display of various bar screens and small and medium-sized screens, various types of industry users (such as bank announcements, recruitment information releases, product information releases, etc.). Under normal circumstances, single-color or two-color display screens generally use asynchronous control systems.