Abstract: In order to clearly understand the basic principle and mechanism of mbedos scheduling, the support characteristics of arm cortex-m4 kernel for real-time operating system is studied. The common scheduling strategies of real-time operating system is analyzed. Using the methods of flow chart analysis and
context core code analysis,this paper focuses on the implementation of three mbedos scheduling strategies, SVC( Supervisor Call) interrupt, pendsv interrupt and systick interrupt. Finally, taking stm32l431 chip of STMicroelectronics as an example, the thread scheduling analysis practice of mbedOS is given. By analyzing the thread scheduling of mbedOS, it is helpful for readers to deeply understand the scheduling mechanism of mbedOS, provide help for the design of multitasking system, and also provide reference for the analysis of other real-time operating systems.

Key words: real time operating system； , scheduling strategy, advanced RISC machines ( ARM) Cortex-M4； , mbedOS； , STM32 chip