According to the needs of network video collection, this paper combines network transmission with video collection, and designs the USB camera video collection with S3C2440 as the core and the video server under the embedded Linux system, thus achieving remote network video information collection.
1 Overall system design
The system is based on the ARM9 processor S3C2440. Under the embedded Linux system platform, the video information is collected through the USB camera, and then the obtained video data is sent to the video server MJPG-streamer through the internal bus. The video server passes the image The compression process is transmitted through Ethernet, and the remote client can access the video server through a browser or special software to browse the on-site information, thereby achieving network video collection. The overall system is shown in Figure 1.
2 System hardware design
The hardware block diagram of the system is shown in Figure 2.
The system processor uses the high-performance ARM9 processor S3C2440. The S3C2440 is a RISC processor based on the ARM920T core. The main frequency is 400 MHz. The MMU is implemented. It has an AMBA bus and a Harvard structure high-speed cache architecture. It has an independent 16 KB instruction cache. And 16 KB of data cache. Mainly used in high-performance, low-cost, low-power embedded devices and handheld devices. The processor integrates complete hardware resources, external storage controller, 4-channel DMA, 3-channel UART, 2-channel SPI, 2-channel USB host and 1-channel USB device, 4-channel PWM timer and internal watchdog timer , 130 GPIO and so on.
NAND FLASH uses K9F2G08. The memory chip has a large capacity of up to 256 MB. The rewriting speed is very fast, easy to use, and has reliable durability. It is suitable for large data storage. The FLASH reads and writes in 512 B blocks. The output interface transfers addresses and commands, and transfers a special data interface to connect to the CPU. The data bus is 8 b. The write operation must be performed in a blank area, so when rewriting data, you must first erase and then write.
NAND FLAsH is used to store bootloader boot code, Linux kernel code and Yaffs file system in this system. SDRAM is a synchronous dynamic random access memory, similar to the memory of a PC. When the system is started, the kernel code is first copied from FLASH to SDRAM for program reading, storage, and execution, thereby improving CPU reading and writing data speed. This uses 2 32MB HY57V as the system memory, connect them in parallel to form a 32-bit data bus, improve the access speed of the CPU, increase the fluency of running the Linux system. Since SDRAM can't save data when power off, it must be constantly refreshed dynamically to save data, and it must be initialized before use.
At present, the most popular Ethernet controller is DAVICOM's DM9000 network card chip, which adapts to 10 Mb / s and 100 Mb / s networks. The processor is connected to the network card through GPIO and supports 3.3 V interface voltage and 32-bit interface memory. It can be directly connected to S3C2440, and the RJ-45 interface can be connected to realize the connection between Ethernet physical layer and data link layer. The device driver can be easily transplanted under the Linux operating system, so this network card chip is selected as the Ethernet controller. The camera uses ordinary USB camera in the market, plug and play, the processor controls the camera through the USB controller.
3 System software design
The system software can be divided into Bootloader, Linux kernel, Yaffs file system and MJPG-streamer video server. The system block diagram is shown in Figure 3.
"Bootloader is a small program that runs before the operating system runs to complete the initialization of hardware devices, so as to bring the system hardware and software environment to a proper state and prepare for the final call to the operating system." The bootloader can be downloaded from the official website of SAMSUNG, and the Bin file is generated after cross-compilation and downloaded to the board.
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