You Don't Need an RTOS (Part 2)

You Don't Need an RTOS (Part 2)

Nathan Jones

Still RelevantIntermediate

In this second article, we'll tweak the simple superloop in three critical ways that will improve it's worst-case response time (WCRT) to be nearly as good as a preemptive RTOS ("real-time operating system"). We'll do this by adding task priorities, interrupts, and finite state machines. Additionally, we'll discuss how to incorporate a sleep mode when there's no work to be done and I'll also share with you a different variation on the superloop that can help schedule even the toughest of task sets.

Summary

Nathan Jones demonstrates how to improve a simple superloop by adding task priorities, interrupts, and finite state machines to achieve worst-case response times nearly matching a preemptive RTOS. The article also explains integrating sleep modes for low-power idle and presents an alternate superloop variant for harder scheduling problems.

Key Takeaways

Implement task priorities in a superloop to reduce worst-case response time for high-priority work.
Use interrupts to immediately service time-critical events while keeping main-loop logic deterministic.
Design tasks as finite state machines to avoid long blocking code and simplify timing analysis.
Incorporate low-power sleep modes with wake-on-interrupt to balance responsiveness and energy efficiency.
Apply an alternate superloop scheduling variant (cooperative/time-sliced pattern) to handle tighter task sets.

Who Should Read This

Embedded firmware engineers and developers with some microcontroller experience who need to decide between a lightweight superloop and an RTOS for real-time and low-power applications.

Still RelevantIntermediate