1. Introduction to Interrupt

Introduction

An interrupt is a mechanism used in microcontroller programming to pause the execution of the current program and call a specific routine or function when a particular event occurs. These events, defined by the programmer, can range from a specific condition on an input pin to a timer overflow or other hardware-defined triggers. Once the routine or function finishes executing, the program resumes from the exact point where it was interrupted.

The Arduino Uno (ATMega328P) provides two primary types of interrupts: External Interrupts and Timer Interrupts. While their functions and triggers differ, they share the same goal: interrupting the main program flow to handle specific events immediately.

External Interrupt

An External Interrupt is triggered by a change in the voltage level on specific input pins of the microcontroller. On the Arduino Uno, there are two pins dedicated to external interrupts: Pin 2 and Pin 3. These are the most commonly used pins when implementing interrupts via the Arduino programming language.

Internal Interrupt

An Internal Interrupt is triggered by modules located inside the microcontroller itself. In the ATMega328P, these are generated by timers and are referred to as Timer Interrupts. A Timer Interrupt is specifically triggered by a timer overflow. The Arduino Uno features three internal timers: Timer0, Timer1, and Timer2. (For more details on how timers operate, please refer to the previous module).