Analyze Current Interrupt Configuration
- Review the existing interrupt handling mechanism in your firmware. Examine the interrupt vector table and ensure that all interrupts and exceptions are correctly mapped.
- Check the configuration of the microcontroller/processor, focusing on the interrupt levels and priority registers.
- Utilize debugger tools to pause execution at various interrupt priority levels, observing order and precedence. Confirm that priority levels correlate with the system design.
Identify Prioritization Issues
- Examine symptoms such as unresponsive hardware or tasks, missed data, and overrunning interrupts, which could indicate improper prioritization.
- Investigate specific cases where low-priority interrupts preempt more critical tasks. This can be observed using tracing tools and logging mechanisms in your development environment.
- Check for priority inversion situations, where higher priority interrupts wait indefinitely for lower priority tasks.
Refactor Interrupt Service Routines (ISRs)
- Ensure your ISRs are designed to execute quickly and perform minimal processing. Offload complex logic to lower priority tasks or deferred work using task schedulers or event flags.
- Refactor lengthy code within ISRs, utilizing flags or semaphore mechanisms that allow main tasks or background tasks to handle in-depth processing.
- Consider re-architecting interrupt flows by using techniques like nested interrupts, where supported, to handle high-priority tasks immediately.
Adjust Interrupt Priorities
Test and Validate Changes
- Conduct thorough testing using simulations of interrupt storms, edge cases, or peak load conditions to verify proper interrupt prioritization.
- Utilize hardware debuggers or logic analyzers to measure interrupt latency and ensure that high-priority interrupts are serviced as expected.
- Review performance metrics and confirm that all critical tasks meet their timing requirements without interruption overruns or missed deadlines.
Implement a Priority Handling Strategy
- Incorporate a dynamic priority adjustment mechanism, if applicable, to handle varying system loads where interrupt priorities might need real-time adjustments.
- Develop a priority ceiling protocol or similar strategy to prevent priority inversion in more sophisticated systems.
- Consider implementing a watchdog for ISR latency, which can trigger system alerts if certain timing thresholds are exceeded.