A new type of the LED screen display data access methods

This paper introduces a new type of LED display obtain data method. This method USES digital processing technology of high precision of the computer display card output analog signal conversion into standard digital signals to display, the realization and computer displayed, is solved by using multimedia card display embarrassing, thereby improving the screen display effect, broaden the display application domain, meet the domestic leading level, and has a certain application value.
Keywords: led screen; VGA interface;  frequency-field

1 introduction
The LED display as a new show media, is a collection of photoelectric and computer technology in the integration of high-tech products. Along with large scale integrated circuit and the rapid development of computer technology, obtained the rapid development, has been widely used in many fields.
In led screen system, most used for transmission, processing, control signal are digital signal, but most current between computer and external display device is through simulated VGA interfaces connected with digital mode, internal computer generated by the display card image information, the D/A (digital/simulation) converter changes for R, G, B tricolor signal and line, field synchronized signal transmission to by cable, signal display device. For analog display devices, such as analog CRT monitor, signal is sent directly to the corresponding processing circuit, drive control tube produce images. And for LCD, DLP display device, such as digital display device which need to configure corresponding A/D (analog/digital) converter, analog signal into A digital signal.
Although now in the market also has many digital display interface products, they have a special computer screens of the digital red, green, blue three gezer signal and the control signal output interface, but these products are most price is higher, sometimes also exist compatibility problems, but also not form a unified standards.
So an analog interface is concerned, display the data obtained method to basically have two kinds: one is through the manufacturer offers special multimedia video card led panel, realize the acquisition data led billboard and computer synchronization display; Secondly, through the simulation signal intercept display card output to get the data, realize the LED display and computer synchronization display. Both techniques have molding products and applied in the actual work led panel.
For the first plan, due to the development of science and technology will lead to all kinds of product rapid renewal, multimedia video CARDS will keep the technical updating and because of the economy, unnecessary waste of resources, thus by market place eliminated. For the second solution, because the display adapters and resolution corresponding to different set requires constant transformation parameters, so product suitability is poor.
Based on the above situation, this paper proposes a method of realizing the led sign and computer displayed new method, can completely replace the multimedia video card, avoid a multimedia video card existing some drawbacks, realization and international display industry standards.
The design principle of the 2VGA conversion interface card
VGA conversion interface card is the basic working principles, adopts A/D collection technology, directly from gm display adapters analog output acquisition image information, no need to install multimedia video card. A simulation signal through the A/D conversion device converted into digital signals, into the screen; Will the other way analog signals through video pre-amplifier still to analog signals to the form, which can make the CRT display monitor display content and LED sign shows content keep real-time consistent, and can monitor the acquisition effect, A/D system, at the same time also reduced by the complexity of the installation, operation. VGA conversion for computer interface card of peripherals can do "no boot installation", thereby improving the system compatibility. The principle structure diagram (see figure 1.

3 the selection of frequency-field chip
ADC (Digital Converter, the abbreviation Analog to produce stats - composed, ADC) as the main components, convert interface card whose main purpose is the input Analog conversion into big screen can recognize the Digital quantity [4]. We use is that the United States AD company latest high-speed, dedicated to RGB video module change device AD9884A - 140 type.
AD9884 is intelligent VGA, SVGA, designate special high-speed (display conversion 500MHz simulation bandwidth) eight A/D conversion chip, to initialize the chip with single-chip computer with the internal registers, the way of writing book serial after work mode, write AD9884 began to work.