How does RTOS context switching work for ARM Cortex-M MCUs?
To understand how RTOS context switching works for ARM Cortex-M MCUs, it’s critical to have foundational knowledge about the primitives the architecture provides to make it possible.
How is hardware designed to support context switching?
We will discuss how the hardware was designed to support this operation, features that impact the context switching implementation such as the Floating Point Unit (FPU), and common pitfalls seen when porting an RTOS to a platform.
Which is the special register for context switching?
After any Thread mode transition from privileged to unprivileged execution, software must issue an ISB instruction to ensure instruction fetch correctness. For context switching, one of the most important special registers is the CONTROL register. Bits in the register read-as-zero unless they are implemented.
What do you mean by context switch in RTOS?
The operation of switching from one task to another is known as a context switch. A Real Time Operating System ( RTOS) will typically provide this functionality. Having a foundational knowledge of how the core of an RTOS works can be a valuable skill set for an embedded engineer to have.
Which is the context switcher in FreeRTOS for interrupt?
We will also walk through a practical example of analyzing the FreeRTOS context switcher, xPortPendSVHandler, utilizing gdb to strengthen our understanding. If you’d rather listen to me present this information and see some demos in action, watch this webinar recording. Like Interrupt? Subscribe to get our latest posts straight to your mailbox.
Is there a FreeRTOS demo for the Kinetis K60?
This page documents a FreeRTOS ARM Cortex-M4 demo application that targets the Freescale Kinetis K60 microcontroller . An IAR project is provided that is pre-configured to run on the TWR-K60N512 controller module. The FreeRTOS plug-in included in the main IAR tools distribution can be used with this demo!
Do you need ewarm v6.20 to use FreeRTOS?
IAR’s EWARM V6.20 or higher is required to open the workspace. The official FreeRTOS zip file download contains source code for all the FreeRTOS ports, and every demo application project. It therefore contains many more files than are required to build and run the Kinetis K60 demo.
How big is address space in ARM Cortex M?
The address space for ARM Cortex-M devices is 32 bits. However, it’s not possible for a branch and link ( bl) instruction to jump across the entire address region (because some bits encode the instruction itself).
Is there a floating point unit in Cortex-M4?
Cortex-M4, Cortex-M7 and Cortex-M33s can implement an optional unit to natively support floating point operations, known as the Floating Point ( FP) extension. Fun fact: The FP extension is itself based off implementations originally defined for ARMv7-A and ARMv7-R architectures, known as VFPv4-D16.