Implementation Of Embedded Video Supervisory System's Device Driver Technology

With the development of video surveillance technology, embedded video supervisory system with its intuitive, user-friendly and rich in content and other characteristics, increases people's attention and concern, and was widely used in many occasions.Wu Han jinglun electronic stock company's four-way video surveillance network server system RT-VS4104, consists of ARM9 processor family EP9315 and digital signal processing chips TM320DM642 dual-processor, and adopts the open-source Linux as its operating system. Its main function is to achieve four-way video monitoring input and one-way video Output. After a brief introduction of the system hardware and system software schematic structure, according to the features of embedded Linux and the requirement of audio processing and alarm management in video supervisory system, we implemented a four-way I2S audio driver and the alarm management driver of a four-way switch.In the audio input module, on the base of the analysis of the M2P/P2M state machine, we designed a double-buffer DMA, used an interrupt based DMA mechanism to control the jumping of the state machine. In addition, we realized the alternative option between the two buffers in our interrupt service routine (ISR). Finally, we implemented the high-speed data transmission between the I2S receiver FIFO and the system memory.In the audio output module, using a similar mechanism, work queue mechanism in Linux kernel, with the bottom half of the interrupt handler, we implemented the output of audio data. Additionally, we designed the structure of the I2S device and a queue structure used to record the audio data buffer block. Once the audio playing process run into the Linux core space through the system call write, it will submit the audio data buffer block to the designed queue, and, at the same time, submit a work to the shared work queue in the Linux kernel, and finally returned to the user space. The work submitted to the shared work queue before is scheduled, completing the audio data buffer block processing, once the CPU is free. Such a mechanism has greatly reduced the required time to submit audio data a time, and improve the efficiency of the system. In the alarm management module, we analyzed the alarm management requirement of the system. Based on the GPIO module and the vectored interrupt module, using the interrupt function supplied by EGPIO, we achieved the input and output control of a four-way switch, and also supplied the kernel interface of poll and access to the switch input device to user.