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PCINT2.md

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This document covers the configuration and usage of Pin Change Interrupt 2 (PCINT2) on the ATmega328 microcontroller. It explains how to enable interrupts for pins PD0–PD7 using PCICR and PCMSK2, how to clear the PCIF2 flag, write the ISR, and apply it in practical applications.

PCINT2 Overview

Group Pins Port Interrupt Vector
PCINT2 PD0–PD7 PORTD PCINT2_vect

Pin Change Interrupt 2 monitors all pins on PORTD. Any logical change (rising or falling edge) on an enabled pin will trigger the interrupt.

PCICR – Pin Change Interrupt Control Register

Bit Name Description
2 PCIE2 Enable Pin Change Interrupt for PCINT2 group

Enable PCINT2 Group:

bitSet(PCICR, PCIE2); // Enable pin change interrupt for PORTD (PCINT2 group)

PCMSK2 – Pin Change Mask Register 2

Bit Name Pin Description
0 PCINT16 PD0 Enable pin change interrupt for PD0
1 PCINT17 PD1 Enable pin change interrupt for PD1
2 PCINT18 PD2 Enable pin change interrupt for PD2
3 PCINT19 PD3 Enable pin change interrupt for PD3
4 PCINT20 PD4 Enable pin change interrupt for PD4
5 PCINT21 PD5 Enable pin change interrupt for PD5
6 PCINT22 PD6 Enable pin change interrupt for PD6
7 PCINT23 PD7 Enable pin change interrupt for PD7

Enable Interrupts for Port D Pins (Examples)

bitSet(PCMSK2, PCINT16); // Enable interrupt for PD0
bitSet(PCMSK2, PCINT17); // Enable interrupt for PD1
bitSet(PCMSK2, PCINT18); // Enable interrupt for PD2
bitSet(PCMSK2, PCINT19); // Enable interrupt for PD3
bitSet(PCMSK2, PCINT20); // Enable interrupt for PD4
bitSet(PCMSK2, PCINT21); // Enable interrupt for PD5
bitSet(PCMSK2, PCINT22); // Enable interrupt for PD6
bitSet(PCMSK2, PCINT23); // Enable interrupt for PD7

You can enable multiple pins simultaneously by setting multiple bits.

PCMSK2 |= (1 << PCINT18) | (1 << PCINT20); // Enable PD2 and PD4

PCIFR – Pin Change Interrupt Flag Register

Bit Name Description
2 PCIF2 Pin Change Interrupt Flag for PCINT2

Clear PCINT2 Flag Manually:

intFlag_clear(PCIFR, PCIF2); // Clear PCINT2 interrupt flag

Note

The flag is automatically cleared when the ISR is executed.

Writing the ISR for PCINT2

The ISR is triggered on any logical change of enabled pins in PORTD. You must read the current pin state and compare it to the previous state to detect rising or falling edges.

Example ISR:

ISR(PCINT2_vect) 
{
    if (bitCheckHigh(PIND, 4)) 
    {
        // Rising edge on PD4
    } 
    else 
    {
        // Falling edge on PD4
    }
}

Complete Initialization Example

void pcint2_Init(void) 
{
    GPIO_Config_INPUT(DDRD, PD4);     // Configure PD4 as input
    bitSet(PCICR, PCIE2);             // Enable PCINT2 group
    bitSet(PCMSK2, PCINT20);          // Enable interrupt for PD4
    globalInt_Enable;                 // Enable global interrupts
}

Summary of PCINT2 Setup

Step Register Action
Configure PDx as input DDRD GPIO_Config_INPUT(DDRD, PDx)
Enable PCINTx in mask PCMSK2 Set PCINTx bit
Enable PCINT2 group PCICR Set PCIE2 bit
Enable global interrupts SREG Set SREG_I bit
Write ISR PCINT2_vect Detect and handle pin changes

Caution

Pin change interrupts are edge-agnostic. You must track previous pin states to determine rising or falling edges.

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