Analyze the Current Interrupt Service Routine (ISR)
- Identify and list down all the ISRs in your firmware. Understanding which ones are causing delays is crucial.
- Use profiling tools to measure the execution time of each ISR. Aim to find any ISR that exceeds a reasonable duration.
- Inspect the source code for each ISR to understand its complexity and logic flow.
Minimize Critical Sections
- Reduce the amount of code executed within Critical Sections. These are often block sections of code in an ISR where no other code can run.
- Avoid the use of mutexes or other locking mechanisms inside ISRs. Locking mechanisms can introduce significant delays.
- If necessary, refactor critical sections by moving code out of the ISR where possible.
Offload Tasks to Background Processing
- Identify tasks executed within the ISR that do not require immediate execution. Move these tasks to the main loop or a lower priority task.
- Implement a simple message queue or a buffer where the ISR can place data for the main loop to process later.
- Use flags or events to signal the main loop that data processing is required outside the ISR.
Use Interrupt Prioritization
- Assign priorities to ISRs so that the most critical interrupts are processed first.
- By using the hardware's natural prioritization capabilities, ensure your system remains responsive.
- Balance priorities to avoid interrupt starvation, where less critical interrupts are never serviced.
Optimize ISR Code
- Ensure that your compiler optimization settings are appropriate for ISR code to reduce execution time.
- Refactor and simplify complex logic within ISRs. Avoid loops or recursive function calls.
- Utilize inline functions instead of standard function calls to reduce overhead time.
- Make use of volatile keyword for variables shared between ISRs and other code to prevent optimization issues.
Use Interrupt Vectors Wisely
- Directly manipulate hardware registers in ISRs when needed, instead of using higher-level abstractions which can be slower.
- Ensure that ISR vectors are correctly configured in your vector table, avoiding unnecessary ISR calls.
Test and Validate Changes
- After making changes to the ISR, perform thorough testing to ensure the modifications haven’t introduced new issues.
- Use hardware-debugging tools to monitor ISR execution times and check for unintended behavior.
- Continuously measure and log ISR durations to ensure they meet your performance criteria.
