A new type of the LED screen display data access methods

A new type of the LED screen display data access methods

The LED display as a new show media, is the collection photoelectric and computer technology in the integration of high technology products. Along with large scale integrated circuit and the rapid development of computer technology, obtained the rapid development, has been widely used in all industries.

In LED display system, most used for transmission, processing, control of the signals have digital signals, and most current computer and external display device is through the simulation between VGA interfaces connected inside A computer, digital way to generate display image information, be the D/A video card (digital/simulation) converter into R, G, B signal and line, field tricolor synchronized signal through cable transmission, the signal to display device. For analog display devices, such as simulation CRT monitor, signal is sent directly to the corresponding processing circuit, drive control tube produce images. And for LCD, DLP display equipment, digital display device should be configured with the 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 special computer screen on the digital red, green, blue three gezer signal and control signal output interface, but these products are most price is higher, sometimes there are compatibility problems, but also not form a unified standards.

So for analog interface, display the data obtained method to basically have two kinds: one is through the manufacturer offers special multimedia video card LED display data collection, realize the LED display and computer synchronous display; The second is through the simulation signal intercept the display card output to get the data, realize the LED display and computer synchronous display. Both techniques have molding products and used in LED display in the actual work. For the first plan, due to the development of science and technology will lead to all kinds of product rapid renewal, multimedia video card will be because of the constantly update technology unnecessary financial and the waste of resources, thus be out by the market. For the second option, due to the resolution of the display adapters and corresponding to different set of continuous to transform set parameters, so that the adaptability of the product is very poor.

Based on the above, this paper puts forward a realize the LED display and computer displayed, the new method can completely replace the multimedia video card so as to avoid the multimedia video card existing some drawbacks, realization and international display industry standard of the world.

2 VGA conversion principle of design interface card

VGA conversion interface card is the basic working principles: the A/D collection technology, general card directly from the simulation output image information collection, no need to install multimedia video card. All the way to the analog signals A/D conversion device converted into digital signals, into the screen; Will the other all the way the analog signals video preamplifier still to the form of analog signals to CRT monitor, so can make the display of the content and LED display shows that the content of the agreement, and can keep real-time monitor the acquisition effect, A/D system, and also reduce the complexity of the installation, operation. As the computer interface card VGA conversion peripherals can do it "didn't turn on installation", so as to enhance the compatibility of a complete system.

3 module selection of transition chip

ADC (Analog-Digital Converter, the abbreviation ADC), as the main components of conversion interface card, its main effect is the input Analog conversion into big screen be able to recognize the Digital quantity [4]. We use the latest high-speed AD company, specialized in RGB video module change device AD9884A-140 type.

AD9884 is intelligent VGA SVGA, XGA display conversion, special high-speed (500 MHz simulation bandwidth) eight A/D conversion chip, want to use single chip initialization of the chip inside the deposit, in A serial way into work mode, write the book after AD9884 began to work.

To better use a new device, the device must be first the operation principle, performance index, limit working parameters and the typical circuit is connected to understand clearly. If is intelligent devices, but must understand its programming characteristics and parameters, and able to be in the market to buy it. Module change device AD9884A is the main interface card, other devices to chip surrounding the chips for choice.

ª¥ [11] ªª AD9884A is a completely eight 140 MSPS integrated circuits, can from the computer and workstations for RGB graphics signal. Its 140 MSPS coding ability and 500 Hz the whole power simulation can support bandwidth 1280 x 1024 resolution and 75 Hz ac frequency refresh, obtained and digital each pixel.

In order to waste energy consumption and system fall to lowest, AD9884A contains a internal + 1.25 v voltage reference, from HSYNC PLL produce a pixel clock, programmable gain, compensation and ground-clamp circuit. The user need only provides a + 3.3 v power supply, the analog input, HSYNC signal. Three states CMOS output can be from 2.5 v to 3.3 v power supply.

The phase lock loop AD9884A PLL from HSYNC signal input produce a pixel, pixels clock the output of the clock frequency range from 20 MHz to 140 MHz. When there is no HSYNC signal, COAST signal to exist, to maintain it's output PLL frequency. AD9884A provide 32 magnitude sampling phase adjustment. Data, HSYNC signal and data clock output phase relationship is at all times maintain consistent. Can use external clock input as pixel clock and do not use the PLL.

Ground-clamp signal from the inside by users to produce or CLAMP input tube feet provided.

ª¤ 4 display data receiving From analogue to digital converter chip output three road RGB digital signal through 50 needle of parallel digital output sockets to display data receiving part Receiving part of the MC3486. Scanning of the double buffering SRAM, every piece of deposit a frame data, a piece of used to receive data writing, another slice of used to scan data read. In frames signal switch v. Data writing listed address sent by the clock counting produce. Line by line signal generated address count. Scan by some of the address crystal and counter produces, address switch with 2 to choose a complete switch.

5 conclusion and future development

The design of the interface card VGA conversion purpose is to solve the multimedia video card embarrassing for the development of the display screen, provide practical solutions. No matter how microcomputer technology development, VGA conversion interface card can with changeless should provide display screen, need to input digital signal parallel. VGA interface card have galaxy multimedia card is all function, at the same time it in standardization has satisfied and international standards requirement, provide higher quality graphics signal. The product has good performance to price, has applied to display in the industry and get a good effect. DVI from the development of the technology we can see digital interface is the future development direction, the LED display technology development put forward a new train of thought. With the popularity of the DVI technology, we can through the compatible simulation, digital signal of the DVI-I interface, that analog signals, and the other to the CRT display all the way through a series of integrated digital signal can be sent into a big screen, to provide a big screen the parallel digital signals. By then, LED light technology will enter a new field for the society, provide higher quality all walks of information service.

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