Design Of Embedded OS Based On Cortex CPU

Embedded operating system as the software platform for embedded systems, is an important factor affecting the development of embedded systems. We designed and implemented an embedded operating system—CM3-OS, for the Cortex processor architecture. The system has a small amount of kernel code, good real-time performance, simple operation, easy to transplant, supports a variety of communication methods, etc.CM3-OS operating system kernel includes four modules:task management, time management, memory management and interrupt management. To facilitate the choice of scheduling mode, we use the preemptive/non-preemptive task scheduling mechanism based on priority. Synchronization and communication between tasks use shared memory, semaphores and message mechanism. The system provides precise software timers for users. We improved the real-time performance of the system with efficient interrupt processing functions of Cortex family processors. Using a simple memory management of fixed blocks, we can meet the free memory requirements and avoid system memory fragmentation.CM3-OS supports a variety of communication with embedded TCP/IP and ZigBee protocol stack, extended Bluetooth, WiFi and3G communication module. Under the precondition of meeting the basic communication requirements and maintaining system stability, we clipped protocol TCP/IP and ZigBee stack reasonably. External expansion Bluetooth, WiFi and3G modules ensure system’s Communication and network needs anytime and anywhere.We designed the hierarchical UI system, which is the basis of CM3-OS system’s HCI. Using the phone interface’s style, the operation of main interface and directory display is convenient and flexible. We provided text reading and BMP picture display. It implemented the operational monitoring of the CM3-OS operating system, including the running information of tasks, message management information and the monitoring of task switching time. We used SD card as storage medium and FAT32file system for file management.Finally, we completed the testing for CM3-OS operating system kernel, including the time properties of task management and scheduling, interrupt management, message and signal. We got better results.