Summary of Interrupts in Rust for Embedded Systems

Introduction to Interrupts

What are Interrupts?

• Interrupts are signals that inform the processor about events requiring immediate attention.
• They allow the processor to pause its current tasks and execute a designated piece of code, known as an interrupt handler.

Key Concepts

Interrupt Service Routine (ISR)

• An ISR is a function called in response to an interrupt.
• ISRs should be short and efficient to prevent blocking other interrupts.

Types of Interrupts

• Hardware Interrupts: Generated by hardware devices, such as timers and buttons.
• Software Interrupts: Triggered by specific software conditions, like certain events in the code.

Interrupt Vector Table

• A data structure that holds addresses for all ISRs corresponding to different interrupts.
• The processor uses this table to locate the correct ISR to execute when an interrupt occurs.

Setting Up Interrupts

Enabling Interrupts

• Interrupts must be enabled in the system for the processor to respond.
• This usually involves setting specific bits in control registers.

Writing an ISR

• An ISR must adhere to specific conventions, including being marked with a specific attribute, such as #[interrupt] in Rust.

#[interrupt]
fn EXAMPLE_INTERRUPT() {
    // Code to handle the interrupt
}

Example of Using Interrupts

Using a Timer Interrupt

• Set up a timer to trigger an interrupt at regular intervals.
• Within the ISR, you might toggle an LED or update a variable.

#[interrupt]
fn TIMER_INTERRUPT() {
    // Code to execute when the timer interrupt occurs
    toggle_led();
}

Best Practices

Keep ISRs Short and Fast

• Avoid lengthy processing within an ISR. Use flags or variables to signal the main loop for further processing.

Avoid Blocking Calls

• Do not include functions that may block execution (like waiting for I/O) in ISRs.

Conclusion

Interrupts are a powerful feature in embedded systems programming, enabling responsive and efficient event handling. Understanding how to implement interrupts is essential for developing effective embedded applications in Rust.