Seed: 一個適合網路設備之嵌入式即時作業系統核心

Abstract

嵌入式系統在現代日常生活中到處可見，並且扮演了一個相當重要的角色。嵌入式系統的特點在於它是一個應用程式特定的系統，而且通常硬體資源較為不足。除此之外，有愈來愈多的嵌入式應用程式要求能夠即時地完成自己的工作，並且希望能有與其他系統利用網際網路溝通的能力。 為了能夠滿足以上的系統需求，我們發展了一個支援網際網路的即時嵌入式作業系統，名叫Seed。Seed是一個小尺寸、富有彈性、高效能、具可攜性的嵌入式作業系統核心。此外，Seed核心為了支援即時系統，所提供的服務都是可預測或者固定時間的行為模式。最後，為了能讓系統更進一步能夠有網際網路溝通的能力，我們也移植了一個名叫lwIP的小型TCP/IP 網路溝通協定模組在Seed作業系統上。 Seed作業系統核心目前支援先佔式多工、執行緒彼此間溝通和同步的機制、以及記憶體、定時器、中斷的管理。核心影像檔若包含lwIP大小為75 Kbytes，若是不包含lwIP大小是21 Kbytes。核心的尺寸相當地小因而適合嵌入式系統。然後我們把Seed的效能測量出來，結果顯示出我們的系統相當適合小型的即時嵌入式網路設備。

Embedded systems are ubiquitous and play a significant role in modern daily life. The characteristics of embedded systems are application-specific and scarce hardware resources. Besides, more and more applications in embedded system care not only real-time to complete their works, but also want to own Internet-access capability which allows the devices to communicate with other systems. To achieve these requirements, we developed an Internet-supported embedded real-time operating system called Seed. The Seed kernel is small, flexible, high performance, and portable for embedded system. Besides Seed have deterministic or constant timing behavior to support real-time system. Finally, to enable the Internet-access capability, we ported a small TCP/IP stack, lwIP, to Seed. Seed kernel currently provides preemptive multitasking, task synchronization / communication, and management of memory, timers and interrupts. The size of the kernel image is about 75Kbytes with lwIP, or 21Kbytes without lwIP. It is quite small and suitable to embedded system. The performance results show that Seed is quite suitable for a small real-time embedded network appliance.