Introduction
Interrupts are essential in embedded systems, allowing microcontrollers to respond to external and internal events in real-time. Understanding how to use them efficiently can improve system performance and power management. This blog explores practical examples and best practices to master interrupts.
What Are Interrupts?
Interrupts temporarily halt the normal execution of a program to handle high-priority tasks before resuming normal operations. They can be classified into:
- Hardware Interrupts: Triggered by external events (e.g., button press, sensor data).
- Software Interrupts: Triggered by program instructions (e.g., system calls, timer events).
Hands-On Example: External Interrupt with Push Button
Objective: Toggle an LED using a push-button interrupt instead of polling.
Hardware Required:
- Microcontroller (Arduino, STM32, ESP32)
- Push-button
- LED
- Resistors and jumper wires
Circuit Connection:
- Connect the push-button to an interrupt-capable GPIO pin.
- Connect the LED to another GPIO pin.
Code Example (Arduino):
Explanation:
- attachInterrupt() links the button press to the handleInterrupt() function.
- The interrupt triggers on a falling edge (button press).
- The ISR (Interrupt Service Routine) toggles the LED state.
Best Practices for Using Interrupts
- Keep ISRs Short and Fast:
- Avoid long computations or delays inside the ISR.
- Set flags and process data in the main loop.
- Use Volatile Variables:
- Ensure shared variables between ISR and main code are declared volatile to prevent compiler optimization issues.
- Debounce Inputs:
- Mechanical buttons can generate multiple signals; implement software debouncing using timers or state machines.
- Avoid Serial Communication in ISRs:
- Functions like Serial.print() can cause deadlocks inside ISRs. Use flags instead.
- Prioritize Critical Interrupts:
- Use NVIC (Nested Vectored Interrupt Controller) for priority management in ARM-based microcontrollers.
Conclusion
Interrupts are powerful tools that enhance system responsiveness and efficiency. By implementing best practices and using well-structured code, you can design reliable embedded applications. Stay tuned for more embedded systems insights
