HDMI (High Definition Multimedia) is based on DVI technology and can be seen as an enhancement and extension of DVI technology, which is compatible. HDMI interface can provide up to 5Gbps data transmission bandwidth, meet 1080p resolution, and support all HDTV standards and advanced digital audio formats such as DVDAudio, support multi-channel 96kHz or stereo 192kHz digital audio transmission, and only use one HDMI Wire connection can be used to eliminate digital audio wiring. At the same time, the HDMI interface does not require digital/analog or analog-to-digital conversion before signal transmission, ensuring the highest quality video and audio signal transmission.
Now, HDMI is a special interface for transmitting high-definition signals. The version has been developed from 1.1 to 1.3. Compared with 1.1 and 1.2, there are several new features and functions: (1) Bandwidth is increased from 5Gb/s to 10Gb/. s; (2) color from 24bit to 48bit; (3) support xvYCC wide color gamut; (4) support DOLBY TRUEHD and DTS-HD; (5) new lip synchronization technology to solve the problem of audio and video out of sync; 6) Add a mini interface. Nowadays, the HDMI interface has become an important bridge between display devices and audio-visual devices, and has become the standard for a new generation of digital audio-visual equipment. According to statistics, in 2003, HDMI consumer electronics sales volume was only 250,000 units, and the number of HDMI products equipped in 2007 increased to 150 million units.
However, almost all HDMI interface products are currently limited to digital TV and DVD series products. This article uses the latest HDMI1.3 technology to design an intelligent display controller, which will apply HDMI technology to the LED display industry. The display performance and performance of the LED display has been a big step.
System Structure and Function Overview According to the LED display screen, which has high display performance and effect, and convenient control requirements, the display control system should have sufficient input and output interfaces and remote communication functions. The system structure of our LED display controller based on HDMI1.3 technology is shown in Figure 1. The system can be divided into the following modules according to functions: 6 analog inputs, 2 DVI inputs, 1 VGA input, RS-232 and RS-485 communication, optical fiber data transmission, real-time clock and status indication.
Design of main function modules At present, the display mode of data transmission mainly includes two types: synchronous display and offline display. The LED display control introduced in this paper is a synchronous display system, which uses a set of embedded systems to provide video source for LED display, which can reduce cost, high feasibility and flexibility, and easy construction. .
The main performance indicators of the independent video LED system LED display are field scanning frequency, resolution, gray level and brightness. Obviously, it is necessary to make appropriate trade-offs for these three performance indicators in different applications. Therefore, the field scan frequency, gray level and brightness are usually determined by the controller, and the resolution can be greatly improved by means of the controller array. In the controller realized in this paper, through the form of controller array, two-way optical fiber data output is obtained, and a large LED display control area (2048*768) is realized, thereby realizing a color-complete full-color large-screen LED display.
The independent video LED system is completely out of the control of the computer, and can realize functions such as communication, video playback, data distribution, and scanning control.
The control system can obtain a video stream in RGB format by decoding the video data. Then, through the data distribution unit, the data is separately sent to different LED display controllers, and the controller displays the data provided by the playback unit to the full-color large-screen LED.
Video Data Allocation Scheme Since the controller controls large frame data (for example, 1024*768), it is necessary to allocate data provided by the video source, and correctly send data of different ranks to different controllers.
The LED controller in this system has a gray level of up to 3×12 bits (up to 64G colors can be displayed) and a control pixel of 1024×768 points. Therefore, it is necessary to send the RGB data provided by the front end to three different groups to be implemented by FPGA, and the scheme is as shown in FIG. 2 .
The data correction sub-module receives the data input from the front end, and performs the point-by-point correction on the data and stores it in the SDRAM. The field data is then divided into 8 groups and simultaneously sent to the LED distributor.
In order to facilitate the interface between the modules, it is advantageous to synchronize data in different clock domains. The system uses SDRAM as the main memory. SDRAM has the advantages of large capacity, high bandwidth, and low price; however, the control is complicated, and there are multiple control and waiting cycles for each read and write. Therefore, in order to improve efficiency, the burst read and write method of increasing the address is usually used, and the data of any address cannot be read at any time like the SRAM.
This scheme adopts a completely dynamic memory allocation mechanism, that is, when each module requests, if it is not the same field data, it can be allocated a new memory, and once the data of the memory is no longer valid, the memory is released. Thus, each block of memory has its own properties. Bus scheduling is the core part of this module. The bus bandwidth usage must be accurately calculated to ensure that there is no overflow or read error in each storage part.
The input data is corrected point by point. The FPGA reads the input data according to the timing relationship and performs the next processing. Since the parameters of the LED tube cannot be completely consistent during the production process, in order to obtain a good image display effect, the LED tube must be sieved.
Using point-by-point correction technology, the brightness of the LED can be adjusted point by point, and the brightness of the display is increased by a certain level, so that the purchaser can relax the brightness and color requirements of the LED, and the cost of LED procurement is also greatly reduced. . In addition, the point-by-point correction technology adopted by the system can modify the calibration parameters online, so that the LED screen can also modify the calibration parameters after being put into operation, compensate for the influence of the LED tube aging on the display effect, and improve the service life of the LED screen. Therefore, the point-by-point correction technique makes the LED module an ideal solution for the basic components of indoor and outdoor full-color displays.
The point-by-point correction parameters are stored in the SPI memory. After the system is powered up, the MCU first transfers the data to the FPGA, which stores it in the SDRAM. After that, the data entered by the front-end interface can be corrected.
Data transmission When the data is transmitted and transmitted, the signals are transmitted in the form of LVDS (Low Voltage Differential Signal). LVDS transmits data in a differential manner, with stronger common-mode noise rejection than single-ended transmission, enabling long-distance, high-rate, and low-power transmission. The FPGA we use is the Cyclone III series from altera. This family of FPGAs makes it easy to acquire LVDS capabilities through I/O configurations.
Two-way optical fiber data output can ensure that the back-end data supports a large-area screen, thereby realizing a large LED display control area (two 1024*768). This is achieved through Altera's Cyclone III family of FPGAs.
MCU control Because the system adopts MCU+FPGA architecture, real network remote operation can be used not only as a general LED display controller, but also as a large outdoor advertising media network. The FPGA is a very flexible programmable logic device that can be programmed like software to enable flexible and convenient change and development in real time, improving system efficiency.
In order to make the whole LED display control system more user-friendly, the controller includes some auxiliary control parts such as serial port (RS-232, RS-485) communication, infrared control, SPI memory and real-time clock. In addition, an LCD display has been added to simultaneously display the LED screen display content.
In short, the addition of these auxiliary control parts makes the entire control system smarter, coupled with the system software we developed and designed by ourselves, which is more user-friendly and easy to use and operate.
In summary, the LED display control system provides 6 analog inputs and 2 DVI input interfaces, supports RS-232 and RS-485 interfaces, enables real-time data acquisition and transmission, and can remotely switch to field devices. Quantity control. The experimental test results show that the brightness of the system is suitable, the resolution is fine (64G color), the field scanning frequency is high (about 400Hz), and the pixel height is high (2048*768 points), which can be used for outdoor broadcast applications. The design is calibrated by a single point, which allows the purchaser to relax the LED's brightness and color requirements, and the cost of LED purchases is reduced; from 8 to 12 bits, the color level of the image is greatly increased. In addition, in addition to receiving signals from the serial port, data signals can also be received via the HDMI interface.
Figure 1. LED display controller structure based on HDMI technology
Figure 2. Video data distribution scheme
Now, HDMI is a special interface for transmitting high-definition signals. The version has been developed from 1.1 to 1.3. Compared with 1.1 and 1.2, there are several new features and functions: (1) Bandwidth is increased from 5Gb/s to 10Gb/. s; (2) color from 24bit to 48bit; (3) support xvYCC wide color gamut; (4) support DOLBY TRUEHD and DTS-HD; (5) new lip synchronization technology to solve the problem of audio and video out of sync; 6) Add a mini interface. Nowadays, the HDMI interface has become an important bridge between display devices and audio-visual devices, and has become the standard for a new generation of digital audio-visual equipment. According to statistics, in 2003, HDMI consumer electronics sales volume was only 250,000 units, and the number of HDMI products equipped in 2007 increased to 150 million units.
However, almost all HDMI interface products are currently limited to digital TV and DVD series products. This article uses the latest HDMI1.3 technology to design an intelligent display controller, which will apply HDMI technology to the LED display industry. The display performance and performance of the LED display has been a big step.
System Structure and Function Overview According to the LED display screen, which has high display performance and effect, and convenient control requirements, the display control system should have sufficient input and output interfaces and remote communication functions. The system structure of our LED display controller based on HDMI1.3 technology is shown in Figure 1. The system can be divided into the following modules according to functions: 6 analog inputs, 2 DVI inputs, 1 VGA input, RS-232 and RS-485 communication, optical fiber data transmission, real-time clock and status indication.
Design of main function modules At present, the display mode of data transmission mainly includes two types: synchronous display and offline display. The LED display control introduced in this paper is a synchronous display system, which uses a set of embedded systems to provide video source for LED display, which can reduce cost, high feasibility and flexibility, and easy construction. .
The main performance indicators of the independent video LED system LED display are field scanning frequency, resolution, gray level and brightness. Obviously, it is necessary to make appropriate trade-offs for these three performance indicators in different applications. Therefore, the field scan frequency, gray level and brightness are usually determined by the controller, and the resolution can be greatly improved by means of the controller array. In the controller realized in this paper, through the form of controller array, two-way optical fiber data output is obtained, and a large LED display control area (2048*768) is realized, thereby realizing a color-complete full-color large-screen LED display.
The independent video LED system is completely out of the control of the computer, and can realize functions such as communication, video playback, data distribution, and scanning control.
The control system can obtain a video stream in RGB format by decoding the video data. Then, through the data distribution unit, the data is separately sent to different LED display controllers, and the controller displays the data provided by the playback unit to the full-color large-screen LED.
Video Data Allocation Scheme Since the controller controls large frame data (for example, 1024*768), it is necessary to allocate data provided by the video source, and correctly send data of different ranks to different controllers.
The LED controller in this system has a gray level of up to 3×12 bits (up to 64G colors can be displayed) and a control pixel of 1024×768 points. Therefore, it is necessary to send the RGB data provided by the front end to three different groups to be implemented by FPGA, and the scheme is as shown in FIG. 2 .
The data correction sub-module receives the data input from the front end, and performs the point-by-point correction on the data and stores it in the SDRAM. The field data is then divided into 8 groups and simultaneously sent to the LED distributor.
In order to facilitate the interface between the modules, it is advantageous to synchronize data in different clock domains. The system uses SDRAM as the main memory. SDRAM has the advantages of large capacity, high bandwidth, and low price; however, the control is complicated, and there are multiple control and waiting cycles for each read and write. Therefore, in order to improve efficiency, the burst read and write method of increasing the address is usually used, and the data of any address cannot be read at any time like the SRAM.
This scheme adopts a completely dynamic memory allocation mechanism, that is, when each module requests, if it is not the same field data, it can be allocated a new memory, and once the data of the memory is no longer valid, the memory is released. Thus, each block of memory has its own properties. Bus scheduling is the core part of this module. The bus bandwidth usage must be accurately calculated to ensure that there is no overflow or read error in each storage part.
The input data is corrected point by point. The FPGA reads the input data according to the timing relationship and performs the next processing. Since the parameters of the LED tube cannot be completely consistent during the production process, in order to obtain a good image display effect, the LED tube must be sieved.
Using point-by-point correction technology, the brightness of the LED can be adjusted point by point, and the brightness of the display is increased by a certain level, so that the purchaser can relax the brightness and color requirements of the LED, and the cost of LED procurement is also greatly reduced. . In addition, the point-by-point correction technology adopted by the system can modify the calibration parameters online, so that the LED screen can also modify the calibration parameters after being put into operation, compensate for the influence of the LED tube aging on the display effect, and improve the service life of the LED screen. Therefore, the point-by-point correction technique makes the LED module an ideal solution for the basic components of indoor and outdoor full-color displays.
The point-by-point correction parameters are stored in the SPI memory. After the system is powered up, the MCU first transfers the data to the FPGA, which stores it in the SDRAM. After that, the data entered by the front-end interface can be corrected.
Data transmission When the data is transmitted and transmitted, the signals are transmitted in the form of LVDS (Low Voltage Differential Signal). LVDS transmits data in a differential manner, with stronger common-mode noise rejection than single-ended transmission, enabling long-distance, high-rate, and low-power transmission. The FPGA we use is the Cyclone III series from altera. This family of FPGAs makes it easy to acquire LVDS capabilities through I/O configurations.
Two-way optical fiber data output can ensure that the back-end data supports a large-area screen, thereby realizing a large LED display control area (two 1024*768). This is achieved through Altera's Cyclone III family of FPGAs.
MCU control Because the system adopts MCU+FPGA architecture, real network remote operation can be used not only as a general LED display controller, but also as a large outdoor advertising media network. The FPGA is a very flexible programmable logic device that can be programmed like software to enable flexible and convenient change and development in real time, improving system efficiency.
In order to make the whole LED display control system more user-friendly, the controller includes some auxiliary control parts such as serial port (RS-232, RS-485) communication, infrared control, SPI memory and real-time clock. In addition, an LCD display has been added to simultaneously display the LED screen display content.
In short, the addition of these auxiliary control parts makes the entire control system smarter, coupled with the system software we developed and designed by ourselves, which is more user-friendly and easy to use and operate.
In summary, the LED display control system provides 6 analog inputs and 2 DVI input interfaces, supports RS-232 and RS-485 interfaces, enables real-time data acquisition and transmission, and can remotely switch to field devices. Quantity control. The experimental test results show that the brightness of the system is suitable, the resolution is fine (64G color), the field scanning frequency is high (about 400Hz), and the pixel height is high (2048*768 points), which can be used for outdoor broadcast applications. The design is calibrated by a single point, which allows the purchaser to relax the LED's brightness and color requirements, and the cost of LED purchases is reduced; from 8 to 12 bits, the color level of the image is greatly increased. In addition, in addition to receiving signals from the serial port, data signals can also be received via the HDMI interface.
Figure 1. LED display controller structure based on HDMI technology
Figure 2. Video data distribution scheme
Yixing Futao Metal Structural Unit Co. Ltd. is com manded of Jiangsu Futao Group.
It is located in the beach of scenic and rich Taihu Yixing with good transport service.
The company is well equipped with advanced manufacturing facilities.
We own a large-sized numerical control hydraulic pressure folding machine with once folding length 16,000mm and the thickness 2-25mm.
We also equipped with a series of numerical control conveyor systems of flattening, cutting, folding and auto-welding, we could manufacture all kinds of steel poles and steel towers.
Our main products: high & medium mast lighting, road lighting, power poles, sight lamps, courtyard lamps, lawn lamps, traffic signal poles, monitor poles, microwave communication poles, etc. Our manufacturing process has been ISO9001 certified and we were honored with the title of the AAA grade certificate of goodwill"
Presently 95% of our products are far exported to Europe, America, Middle East, and Southeast Asia, and have enjoyed great reputation from our customers,
So we know the demand of different countries and different customers.
We are greatly honored to invite you to visit our factory and cheerfully look forward to cooperating with you.
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YIXING FUTAO METAL STRUCTURAL UNIT CO.,LTD( YIXING HONGSHENGYUAN ELECTRIC POWER FACILITIES CO.,LTD.) , https://www.chinasteelpole.com