/*   Filename: intEx1   
Author:    Renier Del Rosario
Date:    22/4/2024
Description:  interrupt detector for push button
*/

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>
#include <util/delay.h>

// Function prototype for initializing external interrupt PCINT0
void pcint0_init(void);
#define DEBOUNCE_DELAY_MS 50

volatile uint8_t lastState = 0xFF; // Initialize to all high (not pressed)
volatile uint8_t currentState = 0xFF; // Current state of PB0 to PB7

#define mask 0b11110000
volatile unsigned char SwitchState = 0x00;

// Global variables
volatile unsigned char PinChange = 0;  // Initialized to False
volatile unsigned char counter = 0;     // Global variable for debugging

// Main function
int main(void) {
    Serial.begin(9600);
    // User initializations
    DDRB = 0x00;  // Configure only PB0 (PCINT0) as input
    PORTB = 0x0F; // Activate pull-up resistor on PB0~PB3 
    DDRA = 0xFF;  // All Port A pins configured as output

    // Initialize external interrupt PCINT0
    pcint0_init();
    PORTA = mask;
    // Infinite loop
    while (1) {
        // Check if pin change detected
        if (PinChange) {
            // Toggle PA7 (LED or output)
            PORTA = mask ^ SwitchState;
            _delay_ms(1000);
            PORTA = 0xF0;

            // Reset pin change detection
            PinChange = 0;
        }
    }
}

// Function definition for initializing external interrupt PCINT0
void pcint0_init(void) {
    cli();                       // Disable interrupts
    PCICR |= (1 << PCIE0);       // Enable PCINT0 interrupt
    PCMSK0 |= (1 << PCINT0) | (1 << PCINT1) | (1 << PCINT2) | (1 << PCINT3);    // Enable interrupt on PB0
    PCIFR |= (1 << PCIF0);       // Clear interrupt flag for PCINT0
    sei();                       // Enable interrupts
}


ISR(PCINT0_vect) {
    // Read the state of PB0 ~ PB3
    uint8_t pb0State = PINB & (1 << PB0);
    uint8_t pb1State = PINB & (1 << PB1);
    uint8_t pb2State = PINB & (1 << PB2);
    uint8_t pb3State = PINB & (1 << PB3);

    currentState = PINB;

    // Check for a valid state change after debounce delay
    if (currentState != lastState) {
        _delay_ms(DEBOUNCE_DELAY_MS); // Debounce delay

        // Read the state again after debounce delay
        currentState = PINB;

        // Check if the state remains the same after debounce
        if (currentState != lastState) {
            // Update lastState to reflect the valid state change
            lastState = currentState;

    // Check if PB0 is pressed
    if (pb0State == 0) {
      Serial.println(PINB);
        // PB0 is pressed
        Serial.println("Button PB0 is pressed");
        SwitchState = 0b11110001;
        // Add your code here for handling PB0 press
    }

    // Check if PB1 is pressed
    if (pb1State == 0) {
      Serial.println(PINB);
        // PB1 is pressed
        Serial.println("Button PB1 is pressed");
        // Add your code here for handling PB1 press
         SwitchState = 0b11110010;
    }

    // Check if PB2 is pressed
    if (pb2State == 0) {
      Serial.println(PINB);
        // PB2 is pressed
        Serial.println("Button PB2 is pressed");
        // Add your code here for handling PB2 press
       SwitchState = 0b11110100;
    }

    // Check if PB3 is pressed
    if (pb3State == 0) {
      Serial.println(PINB);
        // PB3 is pressed
        Serial.println("Button PB3 is pressed");
        // Add your code here for handling PB3 press
        SwitchState = 0b11111000;
    }
        }}

    // Clear the pin change flag
    PinChange = 1;
    PCIFR |= (1 << PCIF0);
    
}