Foreword

With the development of information technology, the traditional simulation system of digitized increasingly many replacement, digitization makes the monitoring system of the long-distance video not need specially erecting the circuit, employing the existing communication line can realize the low-cost information transmission, compared with traditional simulation monitoring system, the intersection of group and network of it cost reduce greatly and systematic the intersection of volume and weight reduce, run, maintain easy greatly.

There are many kinds of communication lines used, for instance: Ethernet, ISDN, xDSL, public telephone network, wireless telephone network,etc., on the basis of the bandwidth of the circuit, the picture quality of the monitoring system of the long-distance video differs widely too.

This text employs putting forward the solution to low equipment cost, low operating cost and ultra and remote video monitoring system, use ARM embedded processor and Linux operating system to construct the embedded system, develops the long-distance video monitoring system that can be employed actually, suitable for low resolution ratio, low cost, control application at a long distance.

Its characteristic is as follows,

Construct ARM embedded processor developing platform, has proposed the low cost of the embedded system and developed the procedure;
The front uses cheap integration to integrate the digitized video to gather the module high, the design of the front of reduced system, has reduced the cost of front greatly;
Write the simple embedded operating system procedure, load the application program dynamically, accelerate its carrying out the speed;
Deal with and use the embedded system constructed by high-speed, high-performance ARM processor in signal, realize by software the picture is compressed.
ARM video monitoring system platform

This subject demands to set up low-cost picture data to gather, compress and convey the system long-rangely in real time, and it is apt to carry on development and debugging under the environment of the laboratory to require; In addition consider the expansion for the future requires, need to possess the memory and managing the unit MMU With the interface of the audio frequency.

EP7312 of CirrusLogic Company is suitable for the requirement. It is the embedded microprocessor based on ARM720T kernel, runs on 74MHz IntelPentium chip of its performance and 100MHz is basically about equal, and the consumption is very low, under 74MHz operating frequency, consumption 90mW, have MMU, audio frequency interface and LCD controller.

Fig. 1 is the developing platform where the video controlled the application system. The system of ARM expands trough and apparatus and expands the trough, used for add the interface such as interface of Ethernet, interface of data storage with enormous capacity and PCMCIA or is used in with other functional development boards ARM systemming, have expanded CMOS picture to obtain function and VGA to reveal the function for ARM system. Among them, VGA interface realizes 320* 240* 12bits through the resistance network, namely 4096 color color reveals. The register that it is relevant to visit with SRAM is as follows, SRAM control register, read address low 16, read address high 16, read the intersection of data and register, write address low 16, write address high 16, write into the register of the data; The register related to the fact that CMOS picture is gathered has CMOS to gather and control register, CMOS to gather the state register; The one related to the fact that VGA reveals is that VGA reveals that controls the register.

Fig. 1 ARM video controls the developing platform

ARM controls CMOS picture to be gathered, then ARM buffers from the picture reading the picture data LCD in SRAM within ARM reveals the storage area, reveal on LCD screen. To the passway before this has just got through the whole data, ARM can be further compressed and transmitted after obtaining the picture.

ARM procedure making

ARM video monitoring system allocates FLASHROM of 512KB, used in the memory of the procedure, so the total of application program and initial data must be smaller than 512KB. The following is ARM procedure making procedure:

The writing of software, with the debugging

To employing writing various necessary procedures, use ADS ARMDeveloperSuite Set up the intersection of project and file, pair write kind * assembler. S file, C language procedure *. C file, *. H file added into project. Then pay setting up correspondingly in compiling the parameter and compile the project file and can carry out the binary scale code to produce after compiling and passing. Use ADW debug, compile project already, software debug can only debug ARM order, unable artificial ancillary equipment; After debugging and passing, plan to download the executable binary scale code, carry on the hardware test.

Realization which the procedure downloads

Realize, programme to the intersection of FLASH and the intersection of procedure and memory by bootloader procedure, bootloader procedure write of oneself on the basis of start little procedure under the way inside.

1Let within the EP7312 starting waying, running at first, PC pass bunches of mouthfuls of 19600bps Receive ” <"??,

2Then PC sends bootloader procedure of 2KB to EP7312 from one bunch of mouths.

3Bootloader procedure begin, run at this moment, PC pass bunches of mouthfuls of 1115200bps Send ” 0×79″ Set up the connection with EP7312 again, PC sends subsequently” 0xFF0xFA” Order, EP7312 returns ” Len: ” ,PC sends the file length data to be downloaded of the four bytes again. Then PC continues sending the whole procedure downloaded, will receive after sending and finishing ” Ok! ” ,Then programming will be received after finishing ” Done! ” Indicate that downloading programming operation succeeds in finishing.

4Start way, start EP7312, can run procedure that just download again at this moment.

The above carries on the basic procedure that ARM employ procedure making by way of project, if applies in using the course actually to the new device and also needs a hardware to debug stage, can further develop the application program after the hardware is debugged and passed.

The software methods of relevant hardware debugging

In case of not having the hardware developing instrument, can carry on the debugging of the hardware by one bunch of mouths, EP7312 and connection of the peripheral hardware basically have three ways: The direct bus connects, sets up the specialized pin to connect, connect the common I/O pin of EP7312 with slice of EP7312.