Implementation of video message terminal equipment

The realization of intelligent community property video message terminal equipment

Abstract: starting from the current reality of residential communities in China, using video superimposer to improve community monitoring management, this paper puts forward a new concept of intelligent community video message transmission and superimposition, and introduces the sd03c03 character superimposition chip and the software and hardware implementation of community video message terminal equipment

key words: data overlay image monitoring system video message

in recent years, with the sustainable development of the national economy, there have been many high-grade intelligent communities. A remarkable feature of these new communities is that cameras are installed at street corners and at the door of each building as surveillance equipment, and each household has a video surveillance screen. On the one hand, when a guest visits, the guest can request the owner to open the door through the communication at the door. At this time, the owner can judge whether the visitor knows it by monitoring the screen and decide whether to let him in; On the other hand, the property management company can transfer these monitoring signals back to the main control center according to the actual needs, so as to quickly respond to any accidents at the owner's place and ensure the personal and property safety of each household. At present, the level of community management has been greatly improved, but there are still many unsatisfactory places. For example, the payment of various public utility fees can only be notified by property management personnel or written on the blackboard at the door of each building, which is neither convenient nor effective. To solve this problem, this paper proposes to apply video overlay chip [1] (VAD) to the community monitoring system, so that the property company can transmit all kinds of messages to the owners through the existing monitoring signal channels in the community, and display them on the owners' monitoring screens. 10. Open the oil return valve. After comparing various VAD chips on the market, sd03c03 chip of Shanghai Volkswagen chip Microelectronics Co., Ltd. is selected for this design

1 overall overview of the system

after a specific understanding of the property management situation in each community, a complete system is designed, which takes the PC of the property company as the control center and the video message terminal equipment in each owner's home as the sub module, as shown in Figure 1. The property company can send SMS messages to the designated users through the PC, and the owner can easily browse and control through the terminal equipment in his home. Table 1 frame format

Figure 1 block diagram of video short message terminal equipment

1.1 serial port communication mode

this system adopts asynchronous communication form, the rate is 9600bit/s, and each byte of data is transmitted with 11 bits: 1 bit start, 1 bit stop, 1 bit check and 8-bit data. The handshake signal is added in the data transmission, which greatly improves the reliability. Information is sent and received in the form of frames. A complete information frame is composed of continuous byte sequences, and has clear start and end marks, so that the receiver can recognize a complete frame. The frame format specified in the protocol is shown in Table 1

communication protocol can only be used as the basis for realizing information interaction, and more importantly, the selection of specific interface mode. The system is used to improve community property monitoring and management. The property management control room uses the originally paved monitoring signal communication channel as the signal transmission bus to transmit some simple video messages to each household, so the bus type rs-485[2] is selected as the communication interface: the property PC management host is used as the upper computer to send serial communication information; Each user's video short message terminal, as the lower computer, uses the single chip microcomputer to receive their own information. The management host can not only send messages in broadcast mode, but also realize point-to-point communication. Each household has its own corresponding address, and the master-slave communication is realized through handshake signal. Figure 2 shows the basic communication mode

Figure 2 Schematic diagram of system serial port communication

1.2 function introduction

the core of intelligent community property video message device is video overlay chip sd03c03, which realizes the following basic functions (see Figure 1): (1) correctly communicate with PC according to the specified protocol to realize the sending and receiving of multi page information; (2) Through the addressing of sd03c03, the characters sent by the property PC are continuously taken out from the self built word library, and the specified characters are superimposed on the video; (3) The owner can normally operate the received short message through the keyboard, which is divided into three keys for different operations according to the actual situation of the user: key 1 completes the page up display of characters; Press key 2 to turn the page down to display characters, and press key 3 to delete the read SMS; (4) It can respond to sudden power failure in time, and can still read the information originally stored in the system after reset. The hardware circuit and software part of the most important video message terminal equipment in the system are introduced below

2 hardware circuit design of video short message terminal equipment

2.1 introduction to video overlay chip sd03c03

sd03c03 chip is a system chip launched by Shanghai Volkswagen chip Microelectronics Co., Ltd. which is mixed with digital and analog and can overlay characters on the video signal output by the camera. It can select eight different video display modes through three lines sel2 ~ sel0 according to the needs of users. See Table 2, and it can display up to 8 (lines) × 16 (column) = 128 different 16 × 16 dot matrix characters, and easy to use, powerful. Table 2 sd03c03 mode selection

the chip is composed of several functional units, such as internal timing control, address code generation, superimposed character information processing, video synchronization information processing, self-excited oscillation loop and display mode selection, which are used to convert the character information stored in off-chip EEPROM, single and dual port RAM or flash into information that can be superimposed on the video signal, And the superposition position of characters on the monitor can be adjusted through the internal timing control function unit. The character superposition device composed of sd03c03 chip works in the image monitoring system composed of camera and monitor in a unique hook mode [3], and has no insertion loss to the original system. The low-cost character superposition equipment developed by sd03c03 chip can be used in the monitoring systems with cameras installed in banks, large supermarkets, large parking lots, warehouses, highway toll stations, high-rise elevators, road traffic, residential communities, etc

add a 16 in sd03c03 × 16 dot matrix character information, occupying 32byte of memory. Next, take the character "H" as an example to illustrate the lattice information format and its storage mode in the memory. Assume that the address range of the character "H" in the memory is 0030h~004fh, with a total of 32 bytes. Table 3 and table 4 respectively give the lattice information format of the character "H" and its specific storage format in the memory. Sd03c03 accesses the memory through the address line, reads out the character lattice information and converts it into information that can be superimposed on the original video image. The specific effect will be introduced later. Table 3 character "H" dot matrix information format

Table 4 character "H" memory format

2.2 self built font library circuit

this terminal equipment is used for community video message transmission and overlay display. Since the overlay characters must be able to change arbitrarily, in addition to the standard secondary font, The 100 character icon is also customized to meet the requirements, with a total of about 8000 characters. Each character occupies 32byte space, that is, the information of all data occupies about 300kbyte. If the dot matrix information of these characters is directly transmitted, the overhead of the system will be great, so a 512k ROM is added to save the dot matrix information of these characters and serve as a self built font access device. In this way, the single chip microcomputer only needs to send the corresponding address of the characters received from the upper computer in the self built word library to two pieces of 2K RAM (6116) for paging storage. At this time, the data in RAM is called the offset address of the characters. When the user reads, the ram of the system first outputs the offset address of the character to the EEPROM (at28mc040) storing the self built word library in the process of high-speed dehydration of the washing machine, and then the local ROM outputs the lattice information of the corresponding character. The connection between sd03c03 chip and off chip ram and self built word library is shown in Figure 3. As long as the A5 ~ a11 seven address lines of sd03c03 chip are connected to the off chip ram, the offset address of characters can be found. In this way, the font address is transmitted skillfully, which greatly compresses the data volume of serial communication and greatly reduces the capacity of ram. The system can determine different font contents according to its own needs. Although the cost of the software increases slightly, it is very feasible to consider the overall situation

Figure 3 Schematic diagram of video message terminal equipment (RAM, ROM and sd03c03)

2.3 address switching skills

although it is clever to use off chip ram to access the offset address of the font, in the device, the single chip microcomputer is required to send the offset address of the character in the font to ram to realize the writing function; Sd03c03 chip is also required to transmit its own address information to ram, and the RAM chip outputs the corresponding address to the self built word library chip to complete the reading function. In this way, two different chips will have address conflicts when reading and writing ram, affecting its normal work. In this paper, a special address switching mode is adopted to enable ordinary single port RAM to complete the function of expensive dual port RAM, as shown in Figure 4. Connect two groups of seven bit address buses of the system to two one-of-two chips 74ls257, and the address bus working in the system is switched through the output terminal (ay6 ~ ay0) of 74ls257. When the MCU writes the offset address of characters into RAM, the gating signal 257wr of 74ls257 is low level, and the MCU address lines AA6 ~ Aa0 are selected; When reading data from ROM through sd03c03 chip, 74ls257 strobe signal 257wr is at high level, and then the address lines ab6 ~ Ab0 of sd03c03 chip play a role in the system. This not only completes the function of dual port RAM, but also saves a lot of costs

note: AA is the address bus of single chip microcomputer, AB is the address bus of sd03c03 chip, ay is the address line of off chip ram

Figure 4 address switching circuit

2.4 power down protection circuit

because the video message terminal equipment is installed in the homes of residents in the community, it is impossible to turn on it all the time for 24 hours. The PC management host in the control center of the property company may send messages to the owners at any time regardless of whether the client terminal is turned on or not. In addition, the owners may also suddenly lose power when browsing short messages. In this way, only using external RAM to store data information will cause power loss, which will bring great inconvenience to customers, so there must be a power loss protection circuit (see Figure 1), That is, an external flash ROM stores the offset address of characters in the font to prevent this from happening. Because 12 pages of short messages are displayed, the mode of the chip is maximized, that is, 128 different characters are displayed on each page. Considering the need of system upgrading in the future, the new generation of high-speed flash memory chip AT24C08 of ATMEL company is selected [4]. When sending the character offset address to ram, the MCU stores them in the off chip flash Rom. whenever the device restarts and the program initializes, it automatically reads the information stored in the flash memory before power failure, and empties the external flash ROM while deleting the information. In this way, burning is realized, and the problem of power loss and information loss is well solved

2.5 character superposition and position control circuit

several important modules of video message terminal equipment have been introduced in detail before. As long as a fixed character superposition and position control circuit [5] is added, the whole system can be realized. The character superposition and position control circuit is shown in Figure 3. Terminal equipment as required