Analysis And Improvement An Embedded Kernel On The MCU Of ATmega128

The key of the embedded network technology is an embedded network server that offers an agreement transformation tools for traditional nonstandard equipments and offers the software and hardware to support for users who manage these. With the development of embedded technology, embedded network imprison products appear, which are based on small and low cost microprocessor. But these products were mostly come to develop by the traditional mode of single task, it is not only difficult with the real-time character and dependability of the security system, but also very low to develop efficiency for the complicated applications. According to the requisition for embedded system of network applications, on the more typical equipment platform of hardware based on ATmega128 and software platform of Ethernut operating system, above-mentioned problems are to be researched and discussed in this thesis.At first, the system structure of Ethernut kernel is explained in detail in this thesis, the characteristic of the kernel is summarized by analyzing the task management, task scheduling mechanism, interrupt management, simultaneity and communication mechanism, timer management and memory management in kernel Nut/OS, therefore in order to meet the need of the real-time character system the corresponding tactics are put forward.In this thesis, in order to solve the problem that the kernel Nut/OS real-time character is weaker, the factors influencing real-time character are analyzed, and preemptive scheduling tactics is introduced, at the same time scheduling in ISR is realized. Through the mechanism of search unrepeatable function by the way of setting up overall sign, and through the Exit Critical method realizes repeating solve the problem of using unrepeatable function in non_preemptive kernel. Thereupon, utilizing the software way to solve the problem of one-chip computer ATmega128 does not support interrupt nesting.Secondly, the thesis analyses kernel Nut/OS cause systematic dependability reduce issue because of lacking the memory and protecting the tactics, according to the particularity ofmemory management in the embedded system, compare to the tactics of memory protection in PC, designed the tactics of memory protection based on ATmega128 and expanding tactics.Finally, experiments are made on the above-mentioned hardware platform according to the tactics put forward in this thesis. Context Switching time and interrupt forbid time are compared to each other before and after improvement, and the kernel performance after improving is analyzed.