Along with the multimedia technologies and the network service technology’s rapidly expand, the video frequency monitoring technology in domains and so on electrical power system, telecommunication engine room, factory, municipal transportation, water conservation system, plot public security obtains more and more widespread application. But the DSP technology’s rapidly expand, the video frequency special-purpose processes the DSP chip particularly the development, promoted the multimedia technologies applications greatly. Equator Corporation walks throughout in this domain in the most front, it promotes MAP-CA, BSP-15 and so on special-purpose video processing DSP chip, by its formidable handling ability and in view of video processing’s optimized performance, has obtained the very big success in the field. At the same time, Equator Corporation promotes Dolphin, Tetra, Shark and so on take its special-purpose video processing DSP as the core embedded development platforms, also becomes many video processing equipment’s core.
1 system overall frame
Tetra development board system overall frame as shown in Figure 1, the BSP-15 data bus and the address bus and SDRAM, Flash as well as video input output chip SAA7113 and SAA7121 are connected, carry on the data exchange. Moreover, BSP-15 takes the PCI main line’s main equipment, south the control bridge chip VT82C686B and network chip RTL8139C, expands the IDE connection, the RS-232 serial port, the USB connection, the ISA main line through the south bridge chip substandard to expand the connection. Audio frequency input/output chip through I2S main line control. Because the I/O mouth is limited, therefore other control interface and the data use the I2C main line to complete alternately, including EEPROM, SAA7113 and SAA7112 and 87LPC764 control.
2 systems realize
2.1 rape the control hardware architecture diagram and the principle of work
Rapes control hardware diagram as shown in Figure 2. BSP-15 will first rape the control information for 87LPC764,87LPC764 after the I2C main line transmission the control code explanation, through the serial port retransmits to RS485 connection chip MAX487, thus for the control code through the RS485 connection transmission rapes the camera. Rapes when the camera receives the control code, according to the request carries on correspondingly rapes the operation. Moreover, 87LPC764 has connected on a PCI main line’s broken line, may inform BSP-15 to the BSP-15 application interrupt to rape the control state, as well as transmits other data to the BSP-15 application.
2.1.1 87LPC764
87LPC764 is 80C51 which PHILIPS Corporation produces, accelerates is the essence high performance, redundant reliable and the low price technical grade general embedded microprocessor. Contains 4KB the OPT procedure code controller, 128 byte user RAM memory, 32 byte user code memory. Has full-duplex UART, the inner tube I2C main line control. Also has may by the exterior crystal oscillator or the internal vibration source actuation internal watch-dog timer, its overflow time has 8 level of time selections.
2.1.2 rape the camera
Rapes camera’s raping is one kind installs on the camera strutting the work table, uses in the camera and the strutting joint, rapes has horizontal and the vertical movement function. Generally rapes the camera built-in decoder, follows rapes the control standard agreement, according to the external control signal, may complete assigns the speed the level, the vertical movement, the aperture, the focal distance adjustment, functions and so on camera closure, opening.
2.1.3 rape the controlling agreement
Current quite general rapes the controlling agreement to have PELCO-D which, the PELCO-P agreement the Pyle high company promotes, in addition has companies and so on Tristar Corporation, Sony Corporation special-purpose to rape the formulation in view of it to rape the agreement. In the performance history, considered rapes camera’s compatibility to the different agreement, will rape the control design for to be possible the compatible each kind of agreement general control module. May act according to rapes the camera to renew the supervisory system differently to rape the agreement, realizes support which rapes to each kind.
In the practical application, the PELCO-P agreement is when in the karma of previous existence most popular rapes the controlling agreement, the PELCO-P agreement uses the RS-485 connection to carry on the transmission generally, the baudrate generally between 1200~9 600bps, 1 outset position, 1 stop position, 8 bit data positions, do not have the verification position. Its data transmission form as shown in Table 1. And the address uses in differentiating differently rapes the camera, but four data bytes contained this strip to rape the control command complete information, concrete data meaning as shown in Table 2.
2.2 87LPC764 control procedure design
87LPC764 completes the function are many, including overall situation in electricity replacement and power source control, ledger wall LED control, watch-dog timed control, exterior warning. Moreover in needs in the situation, may expand the I/O mouth, its internal bringing EEPROM may also record each kind of information. In the actual design, as a result of the first edition 87LPC764 procedure use assembly compilation, many functions and the actual request does not tally, therefore in this project, rewrites the 87LPC764 complete code with the C language, revised and has joined the function which needed in view of this project.
The master routine part judgment and the BSP-15 interactive information, program flow diagram as shown in Figure 3. In the chart the receive and the transmission are relative BSP-15 say. 87LPC764 waits for BSP-15 the instruction, once receives the instruction to carry out, if receives the external signal, then the application interrupt, waited for that BSP-15 reads the corresponding information. And the I2C read-write, the serial port read-write, the internal timer use the interrupt mode. Here gives the flow chart is only the partial flows, with rapes the subprograms which the control has nothing to do with, does not make the detailed description.
In 2.3 VxWorks 87LPC764 driver design
The driver part is mainly under the VxWorks operating system, completes is interactive through I2C and 87LPC764, takes the intermediary explanation and transmits by the upper formation application procedure transmission for the 87LPC764 order, as well as informs 87LPC764 feedback’s each kind of information the upper formation application procedure.
Driver flow as shown in Figure 4. First along with the system initiation initialization driver in various part of variables, will interrupt the function with PCI which assigns to interrupt the connection, founds a news formation, then starts to enter the blocking-like waiting status. When 87LPC764 to BSP-15 application interrupt, plunges into the interrupt function entrance, reads a byte through the I2C main line from 87LPC764 the data, and judges whether needs to continue to read. After the read completes, the interrupt function transmits the data to the news formation, then jumps out. When the actuation receives in the news formation’s data, will report to the upper formation application procedure that and transfers by the upper formation application program processing. Moreover, in the driver has provided all related 87LPC764 operation independent functions similarly, may transfer directly by the upper formation procedure, by driver through I2C to 87LPC764 transmit operation order.
2.4 rape the agreement subprogram design
Rapes the agreement procedure mainly to complete four partial contents: Rapes the agreement document analysis, the Flash fever to write, to rape the module initialization, to provide the Web service end control interface. Figure 5 has given the agreement document analysis and the module initialization simple flow, below carries on to these four parts explained specifically: (1) rapes the agreement document analysis. This part is mainly completes the upper formation Web service end rapes the agreement document through the network receive to carry on the transformation. Because rapes the agreement document is the text document, according to certain form writing, therefore the document analysis is mainly the active component ASCII code transforms the text in for the hexadecimal system rapes the control code. And considered the agreement compatible question, in the resolving must mark many flag bits, like address, velocity of whirl code in code piece position, verification byte position and computational method as well as control code code length and so on. the (2)Flash fever writes the function. After raping the agreement document analysis, after will have analyzed to rape the agreement to transfer the first floor Flash fever to write the actuation to burn into the Flash memory, and in the time which needs the agreement from the Flash memory reads out. (3) procedure initialization. After each time starting, the initialization and establishes well needs the variable, will rape the agreement data to deposit according to certain form in the memory. Considered possibly must simultaneously control many different agreements to rape the camera, therefore in the actual project are most may simultaneously support four kinds differently to rape the agreement. Correspondingly, when initialization must transfer the Flash read function, will need or many agreements from Flash reads out, coexisting places in the memory to supply the module use; (4) rapes the connection function. According to Web service end request, when Web service level transfer, will assign to rape the standard agreement to carry on the explanation, must control including the establishment rapes the address, the rotational speed, calculates the verification code, then transfers the first floor driver the control code transmission for 87LPC764, and in the situation which needs informs 87LPC764 to use what kind of baudrate.
This article introduced as a whole develops the platform based on the Tetra hardware in the network video frequency supervisory system to rape the camera control module design with to realize. In the project rapes the module the compatible ability which rapes to each type, as well as may simultaneously monitor many kinds of different types to rape the camera, is this product luminescent spot. This project develops the video frequency supervisory system already put into the market, obtains user’s approval by its perfect function.
Reference
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3 87LPC764 datasheet[Z]. Koninklijke Philips Electronics,2001
4 Equator hardware platforms stingray hardware platform · tetra hardware platform[Z]. Equator Technologies, Inc., 2002
