ARM-Linux and CDMA for remote video surveillance system-ARM-Linux, CDMA-communication industry
Article by jekky
Wireless network with wide coverage, high efficiency, low cost feature, CDMA network data transfer rate up to 200kb / s, in the development of embedded remote to make full use of CDMA wireless network technology and the characteristics of embedded systems built data transfer system especially suitable for remote or remote network traffic conditions do not have regular local use, such as car video surveillance systems, traffic junctions (license plate real-time monitoring), and the city lights of monitoring. Embedded Linux System 1 Embedded system is application-centric, computer technology, software and hardware can be tailored to meet the functional, reliability, cost, size, power consumption, demanding specialized computer systems, embedded systems have no place now not, from the car, home microwave ovens, PDA (digital assistants), television, the industrial production site, Communicate , Apparatus, instruments, automobiles, ships, aviation, aerospace, military equipment, consumer products, can be found embedded system trace. Linux as a desktop system itself, its biggest feature is the operating system and follow the GPL open source code agreement, the core modular design, easy to cut, especially for small embedded systems requirements, the embedded accounted for half of the system. Use the monitoring system’s processor is a high-end SAMSUNG ARM9 core CPU-S3C2410, its a built-in MMU (memory management unit), main frequency up to 203MHz, the system just to run the embedded Linux2.4 duck to water, not only maintains a small embedded system, low power consumption, easy to carry features, but also make full use of the Linux system memory, file, thread management functions, which greatly facilitates the process of development and program implementation of multi-tasking capabilities. 2 monitoring system structure Monitoring system generally can be divided into real-time monitoring and control are two trigger modes, depending on the situation can design appropriate monitoring methods, if the real-time monitoring, will take up more network resources, the relatively high cost of using the trigger mode low running costs, this uses to trigger mode, monitoring the system structure shown in Figure 1. When the case of unusual circumstances, the trigger monitor terminal take a picture, while its internal control module and CDMA module Collaborative operation, complete Internet access (including dial-up, PPP, and CTP / IP protocol processing, etc.), and the image data captured by the package and sent to the control center computer, or sent to the specified E-mail address, control, Log on to the Internet on the center console to run server-side software after the visit by the monitoring point can be made to the picture. 3 hardware system settings To be able to properly run an operating system, hardware, should at least include the CPU, memory and solid-state memory within the system bus and peripheral interfaces, the specific hardware structure shown in Figure 2. SAMSUNG’s S3C2410CPU with three UART, 1 RTC and touch screen interface, also has I2C bus, USBHost, USBDevice the interface, fully meet the needs of the system, and the high cost is a very good choice. Linux system as the share after the cut was very small storage space (only a few MB), we chose NorFlash as a solid memory model is E28F128J3A150, a capacity of 16MB, 16-bit data bus through the exchange of data with the CPU, and use of its top 8MB space (00800000H-00ffffffH) opened up a jffs2 file storage system, storage system configuration files. 64MB of SDRAM for the two K4S561632C, through the 32-bit data bus with the CPU to exchange data. By MAX3232C level conversion chip and the RTL8019 network chip into a RS-232 interface and an Ethernet interface, use the serial cable and Ethernet cable and PC-connected component can be cross-compiler development environment. Through the CPU, integrated USBHost interfaces directly with the USB camera connection, taking into account the monitoring and control module interface requirements, use USB1.1 interface to the infrared camera. Through the CPU on the integrated UART module interfaces directly connected with the CDMAModem to choose affordable AnyData company DTGS-800CDMA module. 4 Software System 4.1 Control Terminal Programming Control terminal software is the core of embedded Linux operating system, all functions are based on the Linux operating system to achieve complete, Linux itself as a desktop system, to enter the field of embedded operating systems, the need to address the problems include hardware support, provide secondary development environment, and small (reduction of the kernel) and so small that the objective is to meet the basic functions of the operating system and user specific needs of the situation, so the kernel as small as possible, as an operating system, Linux kernel is mainly responsible for program management and scheduling, memory management and on the peripheral drivers and management, as Linux kernel with a modular design, many modules can be independently loaded or unloaded, so small is recompiled on the Linux kernel, the compiler carefully embedded devices need to choose the function module, also remove unwanted features, where only serial port driver, USB camera interface driver (including USBHost, USBCore and USBDevice) have dial-up network applications, but also support the PPP, TCP / IP network protocol, the other can be removed so that the system needed to run the kernel significantly reduced to less than 1Mb. Specific programming including Bootloader boot code, device drivers (USB camera interface driver, serial driver), dial-up, PPP and TCP / IP protocol processing, monitoring, control procedures for receiving and transmitting. Control flow shown in Figure 3. A) the system after power-reset. B) Bootloader initialize the CPU, SDRAM, assigned address space. C) Bootloader Linux kernel to extract the compressed file to SDRAM, the same time to control the transfer from the Bootloader to Linux. Linux kernel has two operation modes to choose from. Flash memory can be run directly, also can be loaded into memory to run. Flash memory operating mode is programmed into the kernel executable image to Flash memory, the system boots from Flash memory, an address starts running the kernel into SDRAM continues to run, this approach can reduce memory needs, in fact, many embedded systems use this method, the memory load mode to the kernel of the compressed file stored in Flash memory, the system starts
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