| Linux has been widely used in embedded systems, because Linux is powerful, supports various architectures, open source and modularize designs etc.. But Linux is originally designed as a time-sharing operating system. The practical application of Linux in real-time environment is limited because of its non-preemptive kernel, coarse time granularity, frequently interrupt disable, virtual memory and buffer mechanism. It's necessary to modify the original Linux to meet the real-time requirements.Firstly, the conceptions and the characteristics of embedded system and real-time system have been introduced in the paper. And then this paper analyzes the advantages and drawbacks of using Linux in embedded systems. Based on the above study, we compared different solutions of achieving real-time ability on Linux system. RTAI has been chosen to analyze in detail. Then we design the benchmark program to test the real-time performance of the RTAI, and the results are compared to the original Linux.After investigating the characteristics of the Ethernet and analyzing the disadvantages of the standard Ethernet in real-time communication environment, the paper presents a way to achieve real-time communication based on the Ethernet through using the network protocol stacks on RTAI. The Intel 8255x's real-time driver has been written according to the RTnet driver model to transplant RTnet to the x86 experiment platform.Finally, the real-time performance test has been carried out on the Linux network subsystem and RTnet respectively in the circumstances of different network loads. The test results indicate that, through applying RTAI and RTnet on Linux, the real-time ability of the system can be guaranteed, and the hard real-time requirements can be met. |
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