// PIC18 in C - Versione 0.3 - Dicembre 2014
// Copyright (c) 2014, Vincenzo Villa
// Creative Commons | Attribuzione-Condividi allo stesso modo 3.0 Unported.
// Creative Commons | Attribution-Share Alike 3.0 Unported
// https://www.vincenzov.net/tutorial/PIC18/hello-2.htm

// Reference: PIC18F2431 data sheet

// [1] REGISTER 3-2: OSCCON: OSCILLATOR CONTROL REGISTER - Page 36
// [2] PORTB, TRISB and LATB Registers - Page 116
// [3] REGISTER 10-2: INTCON2: INTERRUPT CONTROL REGISTER 2 - Page 100
// [4] PORTC, TRISC and LATC Registers - Page 119

#include "configurationsbits.h"

#define _XTAL_FREQ 31250 // CPU clock: 31.250 kHz [1]

#define MY_DELAY 2 // Debounce time [ms] - Set as 1 or 2 ms

#define KEY_RISE 2
#define KEY_FALL 3

int button_R4(void); // Return pin 25 (RB4) status - With debounce

void main(void) {

    TRISBbits.RB4 = 1; // Set RB0 pin as input [2]
    INTCON2bits.nRBPU = 0; // Enable all input PORTB pullup [3]

    TRISC = 0; // Set all PORTC pins as output [4]
    PORTC = 1; // Turn on the first LED [4]

    while (1) {
        if (button_R4() == KEY_FALL)
            LATC <<= 1; // Shift PORTC data  [4]
        if (LATC == 0)
            LATC = 1; // Reset PORTC: turn on the first LED [4]
    }
}

int button_R4(void)
// Return pin 21 (RB0) status - With debounce
// Return code: 0        - Pin is low
//              1        - Pin is high
//              KEY_FALL - Pin from 1 to 0 (from the previous call)
//              KEY_RISE - Pin from 0 to 1 (from the previous call)
{
    static unsigned char old_button;
    unsigned char new_button, status;

    __delay_ms(MY_DELAY);
    new_button = PORTBbits.RB4; // Read actual bit [2]

    if (new_button == old_button) // If actual bit equal old bit-> no change
        status = new_button;

    if (old_button && !new_button) // bit value changed
        status = KEY_FALL;

    if (!old_button && new_button) // bit value changed
        status = KEY_RISE;

    old_button = new_button;
    return (status);
}