Interrupt Handling in Robotics & Embedded Systems

1. Introduction

Interrupt handling is a critical aspect of embedded systems and robotics. It allows the microcontroller to respond to events in real-time by temporarily halting the current execution flow. This lesson will cover the essential concepts, types of interrupts, handling processes, and best practices for effective interrupt management.

2. Key Concepts

• Interrupt: A signal that prompts the processor to stop its current execution and execute a specific piece of code.
• Interrupt Service Routine (ISR): A special function that is executed in response to an interrupt.
• Context Switching: The process of saving the state of the current task and loading the state of the ISR.

3. Types of Interrupts

• Hardware Interrupts: Triggered by hardware devices (e.g., timers, sensors).
• Software Interrupts: Triggered by programs via specific instructions.
• Timer Interrupts: Generated by timers to perform periodic tasks.
• External Interrupts: Triggered by external events, such as button presses.

4. Interrupt Handling Process

The process of handling an interrupt can be broken down into the following steps:

            graph TD;
                A[Start] --> B{Interrupt Occurs?}
                B -- Yes --> C[Save Context]
                B -- No --> D[Continue Execution]
                C --> E[Execute ISR]
                E --> F[Restore Context]
                F --> D;
        

The flowchart above illustrates the interrupt handling process, where the system checks for an interrupt, saves the current context, executes the ISR, and finally restores the context to continue normal operation.

            #include 
            #include 

            ISR(INT0_vect) {
                // ISR Code for External Interrupt 0
                PORTB ^= (1 << PB0); // Toggle LED on PB0
            }

            int main(void) {
                DDRB |= (1 << PB0); // Set PB0 as output
                EIMSK |= (1 << INT0); // Enable INT0
                EICRA |= (1 << ISC01); // Trigger INT0 on falling edge
                sei(); // Enable global interrupts

                while (1) {
                    // Main loop
                }
            }
            

5. Best Practices

• Avoid using delays and long computations within ISRs.
• Use flags to indicate the status of an event rather than performing complex actions in the ISR.
• Ensure shared resources are properly managed to avoid race conditions.

6. FAQ