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LED electronic display system design

Release time:2015-04-17 16:29    Publisher:视爵光旭

The development of science and technology, display and computer related equipment connection has become a must. In order to facilitate the application of occasions, display of the application is divided into synchronous and asynchronous, synchronous and asynchronous, the name suggests: synchronization is the control device and display real-time communication, asynchronous control system and LED electronic display independent operation. Synchronous display mode is commonly based on an introduction, the synchronous display.

The overall design, system

The hardware of the system is divided into three parts. First of all, through the display of real time extraction circuit card in real time information from the extracted VGA monochrome digital video signal, the pixel clock, synchronization, frame synchronization, after processing by the output medium in the past; the second part is the

CRT video signal to LED signal conversion circuit, the circuit of the image signal is transmitted over the transmission medium through the selection, storage, distribution, read, converted into a display signal corresponding to the LED dot matrix screen; the third part is the LED driver board, it receives the converted LED

Display signal, and assigned to the corresponding pixels of LED dot matrix screen, LED display driver.

Two, display real-time information extraction circuit

In VGA mode, when the display a color on the VGA in the video memory, first by the output of a color, the color palette is used to select the number in the register, the selected palette registers and a eight bit address index, used to select

The digital to analog converter (DAC color, DAC color register) register a total of 256, each register consists of 18 bits, elected in a color register, and the 18 bit digital signal and analog to digital conversion, converted to analog the red, green, blue

Send signal, analog monitor, to achieve scanning graphics.

When the VGA in the display mode 18, when the sixteen color mode, color palette registers eight index address low four (from P0 to P3) is a digital video signal in blue, green, red and the luminance signal, we can use the VGA

The characteristics of direct extraction, monochrome digital video signal. In the actual circuit, the card through 26 core characteristics of socket to achieve this function. The P0 P7 eight index address, 17 feet, 21 feet, 23 feet were pixel clock, synchronization, synchronization. Characteristics of socket

In terms of the signal to the color register counter analog monitor, on the other hand can output, therefore, our 26 core socket from graphics features directly extracted from a monochrome video signal, the eight string transfer and transformation after the long line transmission out, at the same time, extract

Pixel clock, the field synchronization signal, the line sync signal, convert the signal for the future and display. A eight bit serial / parallel conversion is based on two reasons: one is because in the VGA graphics mode, a pixel consists of eight bits, eight bit parallel output to achieve a pixel

Transmission of a pixel; two is a eight bit serial / parallel conversion reduces the data transmission rate, convenient for long distance transmission.

VGA scanning sequence and LED screen scanning sequence is different, therefore, must display the signal VGA video signal is converted into the corresponding to the LED large screen, which mainly through the two SRAM

(SRAM1 and SRAM2) to read and write to complete. Two pieces of SRAM alternating in reading and writing, assuming that in a field, SRAM1 is in the write, read SRAM2 in the state, at this time, SRAM1 write signal effectively, the read signal is invalid, at the same time, the write address generator.

Students write address strobe input SRAM1, in this way, the digital video signal is written to the SRAM1; for SRAM2, the write signal is invalid, the read signal effectively, at the same time, read the address selection input SRAM2, SRAM2 to read a data has been written, for distribution, transmission

And display.

(a) VGA video signal selection

VGA video resolution and large screen LED different, in this system, we realize the LED large screen resolution of 256 x 128, and VGA in the 18 mode, the resolution is 640 * 480 LED screen, so, cannot completely display the video image, and

Can only choose one part for synchronous display. VGA video image selection, is accomplished by writing the address generator and the read address generator. Write the address in the address generator to produce at the same time, a write control signal, the control signal is selected in a frame

For the effective period, the rest of the time is invalid, so that only the selected line data into SRAM, for the completion of the line selection; similarly, read address generator in at the same time, read address generation a read control signal, the control signal for the selected column read shift only during the

Effect, only read the selected column displacement data, thus completing the VGA video signal selection.

(two), the distribution of SRAM data read

The data stored in the SRAM to read, according to a certain order, distribution, so that it corresponds to a large screen LED, here, we adopt the way that the partitioning circuit, LED large screen in multiples of 16 partitions, LED large screen has a total of 256 lines, it is divided into sixteen

A partition. Read the data distribution according to the following order: the first is the first partition of the first line of the first pixel, then second division of the first line of the first pixel, …... The sixteenth division of the first line of the first pixel, next is the first line of the first partition

Two pixel... According to this order, the data read out by the eight bit shift register and serial output, so that the sixteen partitions of the corresponding position of the simultaneous transmission of data.

The partitioning circuit has two advantages: first, the LED screen is divided into sixteen zones, the data transmission rate is reduced to the original

Preview: Luminous flux in an important position on the display screen Next: Analysis of the advantages and disadvantages of LED display

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