Understanding Interrupt Handling in Microcontroller Programming

Signal to the processor emitted by hardware or software indicating an event that needs immediate attention.

Interrupts play a crucial role in microcontroller programming. They allow a microcontroller to pause its current task and execute a separate routine, before returning to the original task. This article will provide a comprehensive understanding of interrupts, their types, and how to handle them in microcontroller programming.

What are Interrupts?

In the context of microcontrollers, an interrupt is a signal that temporarily halts the execution of the program to execute a separate routine, known as an interrupt service routine (ISR). Once the ISR is complete, the microcontroller returns to the original program. Interrupts can be triggered by both hardware (external interrupts) and software (internal interrupts).

Polling vs Interrupts

Before diving into interrupts, it's important to understand the concept of polling. Polling is a method where the microcontroller continuously checks the status of a device. While this method is simple to implement, it can lead to inefficiencies as the microcontroller has to wait until the device is ready.

Interrupts, on the other hand, allow the device to notify the microcontroller when it's ready. This means the microcontroller can perform other tasks instead of waiting, leading to better utilization of resources.

Types of Interrupts

There are several types of interrupts, including:

1. Hardware Interrupts: These are triggered by external hardware devices. For example, a button press could trigger an interrupt that causes the microcontroller to execute a specific routine.

2. Software Interrupts: These are triggered by software events. For example, a timer reaching a certain value could trigger an interrupt.

3. Priority Interrupts: These allow certain interrupts to have priority over others. This is useful in situations where certain tasks are more important and should be executed immediately when their interrupt is triggered.

Handling Interrupts

When an interrupt is triggered, the microcontroller stops executing the current program and jumps to a predefined location where the ISR is stored. The first step in the ISR is usually to save the current state of the microcontroller, so it can be restored when the ISR is complete.

Next, the ISR performs the necessary actions to handle the interrupt. This could involve reading data from a device, performing calculations, or updating variables.

Once the ISR is complete, the state of the microcontroller is restored and execution of the original program resumes.

Conclusion

Interrupts are a powerful tool in microcontroller programming, allowing for efficient use of resources and responsive interaction with devices. Understanding how to handle interrupts is a key skill for any microcontroller programmer.