Why interrupts are needed in Embedded C

Introduction

Interrupts help a microcontroller stop what it is doing and quickly respond to important events. This makes programs faster and more efficient.

When a button is pressed and the program must react immediately.

When a sensor sends data and the microcontroller needs to read it right away.

When a timer reaches a certain count and the program must perform a task.

When communication data arrives and must be processed without delay.

Syntax

Embedded C

void ISR_Function(void) {
    // code to handle interrupt
}

// Enable interrupt in microcontroller registers
// Attach ISR_Function to the interrupt vector

An ISR (Interrupt Service Routine) is a special function that runs when an interrupt happens.

Interrupts must be enabled in hardware and software to work.

Examples

This ISR runs when a button press interrupt occurs.

Embedded C

void button_press_ISR(void) {
    // code to run when button is pressed
}

This ISR runs when a timer interrupt happens.

Embedded C

void timer_ISR(void) {
    // code to run when timer overflows
}

Sample Program

This simple program simulates an interrupt by calling the ISR function. When the ISR runs, it sets a flag. The main program checks the flag and prints a message.

Embedded C

#include <stdio.h>
#include <stdbool.h>

volatile bool button_pressed = false;

// Simulated ISR for button press
void button_press_ISR(void) {
    button_pressed = true;
}

int main() {
    printf("Program started\n");

    // Simulate button press interrupt
    button_press_ISR();

    if (button_pressed) {
        printf("Button was pressed!\n");
    }

    printf("Program ended\n");
    return 0;
}

Important Notes

Interrupts let your program do other things and still respond quickly to events.

Keep ISR code short and fast to avoid delays.

Use volatile variables to share data between ISR and main code safely.

Summary

Interrupts allow quick response to important events.

ISRs are special functions triggered by interrupts.

Using interrupts makes programs efficient and responsive.