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Introduction With the development of digital technology, LCD TV (LCD TV) related technology has also made rapid progress. Compared with the traditional CRT TV, it has the characteristics of light and portable, rich color, high definition, green, low power consumption and long service life.

This paper takes the LCD TV solution based on DVP-M as an example to introduce the system structure of LCD TV from two aspects of hardware and software.

DVP-M Introduction DVP-M is a liquid crystal TV signal processing chip introduced by Renesas Technology Co., Ltd., which enables LCD TVs to achieve multi-standard signal compatibility. It can integrate Y/C separation circuit, color recovery circuit, I/P conversion circuit and image quality adjustment circuit for integrated signal processing. At the same time, DVP-M also has superior processing capabilities for different TV signals.

Hardware structure analysis
The system is mainly composed of the following units: power supply, IR (infrared remote control) and keyboard, HDMI reception, TV signal reception (Tuner), video processing, sound processing, state storage (EEPROM), master MCU, audio and video terminals and LCD Display unit. The system structure is shown in Figure 1.

The system has eight source input ports: TV, HDMI, VGA, YPbPr, SCART1, SCART2, AV and SIDE AV, as well as TV and AV output (AV OUT).

The M16C of Renesas is used as the master MCU. Except that DVP-M communicates with the MCU through UART, all other controllable ICs and MCUs use I2C serial bus communication. The MCU controls the switching of the signal channels of each AV Switch (Audio/Video switch) by recognizing the key operations of the remote controller and the keyboard, and controls the audio and video processing unit to perform various processing on the signals, and then displays them through the liquid crystal panel, and at the same time, various The operation will set the relevant variables and write them to the EEPROM to remember the current state for use at the next boot.

Figure 1 system hardware structure

Video Processing Unit The main chip of the video processing unit uses DVP-M, which uses its three analog signal channels and one digital signal channel.

The TV signal (from Tuner's second IF output) is output from SCART1 as a SCART TV output (the port will have a TV output whether in TV mode or not), all the way through the M52790 output to the AV OUT port, and all the way to DVP-M The first analog channel.

SCART interface is a European universal video interface with input and output functions. It supports three video signal formats, namely CVBS (composite full TV signal), YC (component video signal) and RGB. The input signal format can be detected by MCU. The level of the FB pin of the interface is RGB if it is less than 1V, otherwise it is CVBS/YC.
AV, SIDE AV and YC/CVBS format signals entering from SCART control the M52790 through the MCU, and select one of them to enter the second analog channel of DVP-M.

The RGB signals entering from SCART (including SCART1 and SCART2) and the non-HD signals of YPbPr (described in the HDMI receiving unit) are selected to enter the third analog channel of DVP-M through the AV Switch FSAV330.
The DVP-M digital channel enters the 24-bit RGB video signal output through the MST3388.

The MCU sets the corresponding DVP register according to the input signal type, completes the DVP-M internal channel selection, image processing, and the like.

The analog signal is subjected to A/D conversion, YC separation (bright color separation), synchronization signal separation and processing, 3D noise reduction processing, IP conversion (interlaced signal into progressive signal), and VBI decoding in the DVP (resolved field blanking period). Teletext and CCD and other graphic information) and so on, and finally mix the OSD information to generate 24-bit RGB digital signals to the LCD panel display. For the input digital signal, the processing is similar to the analog signal except that there is no A/D conversion, YC separation, and synchronization separation.

Figure 2 Software structure diagram

HDMI receiving unit The HDMI unit of this system uses MST3388, which is an HDMI receiver with three RGB/YUV analog signal input ports and one HDMI digital signal input port. All inputs pass through the MST3388 and output 24-bit RGB digital signals.

The HDMI signal is decoded by the MST3388 signal, and the 24-bit RGB digital signal and the I2S audio signal are output and sent to the DVP-M and MSP3410 for processing. The highest resolution supported by HDMI in the system is 1080p.
The VGA and YPbPr signals enter two of the analog signal input ports, respectively. For the VGA input, convert to a 24-bit RGB digital signal and enter the digital channel of the DVP-M. For the YPbPr signal, it is first detected by MST3388. If the resolution is above 720p, it is converted into a digital signal by MST3388 and output to DVP-M, otherwise it is directly input from the analog channel of DVP-M.

The main chip used by the sound processing unit sound processing unit is the MSP3410, which supports almost all analog TV sound signals, such as B/G, L, I, D/K, M/N and FM-Radio, and supports Liyin (NICAM). ) Digital audio standards. It communicates with the MCU via the I2C bus.

The Tuner (TV tuner) sound intermediate frequency (Sound IF) signal is input from the SOUND IF port of the MSP3410. The HDMI decoded sound signal is input from the I2S terminal, and the sound signals corresponding to the VGA and YPbPr signal sources are input from the two sets of SCART ports respectively. The AV and SCART sound signals are controlled by the MCU to control the M52790, and one of them is selected to enter a group of SCART ports.

The processed sound signal is output from the speaker, and the TV signal is output to the SCART1 interface in the system through the SCART1 port of the MSP3410 as a TV output, and other sound signals are output from the MSP3410 SCART2 port to the AV OUT port in the system as an AV output.

In addition, in the automatic search, you need to use the MSP3410 to complete correctly. When searching for the station, you first need to read the sound system of the current TV signal from the MSP3410, and then write the corresponding intermediate frequency data to the Tuner according to different sound systems.

State storage unit The state storage unit, also known as Last Memory. It uses a 32KB EEPROM to store some system status, channel information, status information of each source, and so on.

It mainly includes the following parts: the final signal input mode (such as TV, AV1, HDMI, etc.), the last selected language status (such as English, French, etc.), the final sound information (such as volume, bass, treble, etc.), each The image source corresponds to image brightness, contrast, color, hue and other information, VGA / HDMI display status (horizontal position, vertical position, phase, clock), channel name and frequency of each channel, color system and sound system.
Each time an operation related to the above status information is performed, the MCU updates the corresponding contents in the EEPROM to memorize the current status. When the power is turned on, the MCU reads the contents of the EEPROM and enters the state before the shutdown.

Software structure analysis
The software of this system is based on BOS embedded operating system. It is divided into five tasks and five cycle processing functions according to system requirements. The software structure is shown in Figure 2.

Mainly complete signal state detection, I/O port detection and button processing, and send corresponding requests to other tasks according to different states and key actions.

According to the received request, the EEPROM is read and written, such as reading and writing of the station number, volume, and color adjustment information.

Read and write to the corresponding registers of DVP-M according to the request, complete channel switching, color adjustment, image adjustment, OSD display, etc.

The processing of the display content of the OSD menu (On Screen Display) is completed according to the request and the current state, and a request is sent to the DvpTask, and the OSD related register is written to realize the OSD display.

Control Tuner's channel selection, search and MSP3410's sound decoding and volume control, and I/O port input/output control operations.

This system uses DVP-M as the main video processing chip. Due to its high integration, it simplifies the design of hardware circuits. At the same time, DVP-M also has superior processing capability for different TV signals. The system provides a more flexible software platform and has a large space for application.

1 Qiu Bangneng. RENESAS M16C/62 Embedded Microcontroller Programming [M]. Wuhan: Huazhong University of Science and Technology Press, 2004.
2 DVP-M. R8J66604AXXFP data sheet.