Development Of Operating Status Recorder For Scientific Instrument Based On Embedded Linux

There is a large gap of scientific research foundational condition between China and developed countries. The situation of low rate of instrument utilization and the poor sharing degree also exists with the limited condition. The System of Scientific Instrument Status Monitor Project (No. 2004DKA10010, No. 2005DKA10103) was one of the parts of National Science and Technology Basic Condition Platform Program of China. The system records the objective operating data of scientific instruments, which supporting the effective management and appraisement of scientific instruments.Current methods of scientific instruments operating status monitoring are unable to meet the needs of the monitor system, so when implementing the project, we developed the operating status recorder for scientific instrument in Jilin University. The recorder used an 8-bit MCU as the center controller, which detecting the status of instruments and communications with the project server. The recorder has advantages of high availability and low price. It has monitored many scientific instruments in Beijing, Shanghai and Changchun, played a very good role model. Because of the MCU with less hardware resources, while designing the condensed TCP/IP protocol had been used, it is difficult to extend remote management function, which needs to be resolved.The significance for the development of the recorder based on embedded systems means putting the embedded system technology application to the scientific instruments operating status monitoring and exerting its advantages, expanding the record functions, such as simple remote management; Study of high availability technology of software could be referred by high availability system model.This article researched the development of hardware and software technology of embedded system, on this basis, the scientific instruments operating status recorder based on embedded system was developed. The embedded system structure includes four parts: embedded processor, embedded peripherals, embedded operating system and embedded application software.The paper selected S3C44B0X as the embedded microcontroller, expanded peripheral equipments including a status detection module of photoelectric isolation, SST39VF1601 Flash rom used for program, SDRAM dynamic data memory HY57V641620, NVRAM and Nand Flash, RTL8019 Ethernet interface, SL811HS USB Host interface and power supply, the clock and reset, a wireless LAN function realization was also introduced.μCLinux was used as the embedded operating system. The thesis introduced the development environment onμCLinux and discussed the Bootloader,μCLinux kernel configuration method and the kernel generation, and wrote the hardware device driver and the functional applications based onμClinux, used boa and CGI achieved embedded web server function.The paper used multi-thread technology to divide a complex application procedure into a number of threads, each thread acts a function, the threads communicated through the shared-variable, as all threads are relatively independent, the difficulty of development was reduced, which will also help to improve the system stability.Embedded software application used thread redundancy technology, thread heartbeat detection and watchdog process to achieve high availability. Run N+1 threads at the same time, N online work, and one online backup. When one of the online threads runs failure, the backup thread will take over the thread resources and continue to provide the service. Threads regular send heartbeat signals to system management process, if the management process has not received a heartbeat signal of one thread within the set time, thus the thread is considered being problem and the backup thread would replace it and continue working.Watchdog process monitors health status of management application process, if find management process fail, watchdog process will restart the system management application process. If the watchdog process failures, hardware watchdog counter will not clear, the MCU will reset after the overflow occurs, and reopen the embedded system as a whole resume.Research so far, the mainly work and achievements are here: (1) Designed and realized the hardware circuit; (2) Wrote the hardware driver and the application procedures based onμCLinux; (3) Used multi-thread technology and the high availability design of software to improve the stability.After testing for nearly 10 months in Beijing and Changchun, the result shows that the recorder developed in this paper has the improvement beyond the original recorder in communication function and remote management function.Based on the embedded system research and applications, the article solved operating status monitoring on scientific instruments and network communication, while the research of the monitoring methods and communication technologies can also be applied to other distributed control systems, such as environmental monitoring, Water and oil transportation network monitoring systems.Further work needed: (1) The extension of variety in signal detection of instruments operating status. (2) The anti-cheat function of operating status monitoring on scientific instruments. (3) The extension of the alarm function.