#include <stdio.h>
#include <stdlib.h>
#include <xc.h>
#define _XTAL_FREQ 32000000

// Define Timing
#define T_US 600

// Define IR LED pin
#define LED    LATAbits.LATA5

// Define Buttons (Active Low)
#define BTN_CH_INC_PIN PORTAbits.RA0
#define BTN_CH_DEC_PIN PORTAbits.RA1
#define BTN_VOL_UP_PIN PORTAbits.RA2
#define BTN_VOL_DOWN_PIN PORTAbits.RA3
#define BTN_POWER_PIN PORTAbits.RA4

#pragma config FEXTOSC = OFF,RSTOSC = HFINT32  // HFINTOSC (32MHz)
#pragma config CLKOUTEN = OFF,CSWEN = OFF,FCMEN = OFF
#pragma config MCLRE = OFF,PWRTE = OFF,WDTE = OFF,LPBOREN = OFF
#pragma config BOREN = OFF,BORV = LOW,PPS1WAY = OFF,STVREN = ON
#pragma config DEBUG = OFF
#pragma config WRT = OFF,LVP = OFF,CP = OFF,CPD = OFF

// Function Prototypes
void SYSTEM_Initialize(void);
void PWM5_Initialize(void);
void IR_Send(uint16_t data);

int main(int argc, char** argv) {
    SYSTEM_Initialize();
    
    // Enable Interrupt-on-Change for Wake-up
    // GIE=0: Execution continues after SLEEP (no ISR vector)
    // PEIE=1: Peripheral Interrupts Enabled (required for IOC)
    INTCONbits.GIE = 0;
    INTCONbits.PEIE = 1;

    while(1){
        // 1. Enter Sleep if no buttons are pressed (All inputs High)
        if ((PORTA & 0b00011111) == 0b00011111) {
            IOCAF = 0; // Clear IOC flags
            SLEEP();
            NOP();
        }
        
        // 2. Debounce/Wake-up delay
        __delay_ms(20);

        uint16_t command = 0;
        
        // Check Buttons (Active Low)
        if (BTN_CH_INC_PIN == 0) {
            // RA0: 000010010000
            command = 0b000010010000;
        } else if (BTN_CH_DEC_PIN == 0) {
            // RA1: 100010010000
            command = 0b100010010000;
        } else if (BTN_VOL_UP_PIN == 0) {
            // RA2: 010010010000
            command = 0b010010010000;
        } else if (BTN_VOL_DOWN_PIN == 0) {
            // RA3: 110010010000
            command = 0b110010010000;
        } else if (BTN_POWER_PIN == 0) {
            // Power: 101010010000
            command = 0b101010010000;
        }
        
        if( command != 0 ){
            T2CONbits.TMR2ON = 1; // Start Timer 2
            IR_Send(command);
            T2CONbits.TMR2ON = 0; // Stop Timer 2
            __delay_ms(40);
        }
    }
    return (EXIT_SUCCESS);
}

void SYSTEM_Initialize(void) {
    LATA = 0x00;
    TRISA = 0b00011111; // RA5(bit 5) output , others input
    ANSELA = 0x00;      // All digital
    WPUA = 0b00011111;  // WPUA: Weak Pull Up. Enable for RA0-RA4
    RA5PPS = 2;         // PPS - Peripheral Pin Select. Map PWM5 to RA5
    
    // IOC Setup
    // Enable Negative Edge IOC for RA0-RA4
    IOCAN = 0b00011111; 
    IOCAP = 0x00;
    IOCAF = 0x00;
    PIE0bits.IOCIE = 1; // Enable IOC Interrupt

    // Initialize PWM
    PWM5_Initialize();
}

void PWM5_Initialize() {
    // Using Timer 2 for PWM5
    T2CON  = 0b00000000; // TMR2 OFF (bit 2 = 0), Prescale 1:1
    // Configure Timer 2
    // Fosc = 32MHz. 
    // Target Freq = 40kHz -> Period = 25us.
    // T2PR = [Period / (4 * Tosc * Prescale)] - 1
    // Tosc = 1/32M = 31.25ns.
    // 4 * Tosc = 125ns.
    // 25us / 125ns = 200.
    // With Prescale 1.
    // PR2 = 200 - 1 = 199.
    PR2    = 199;
    // PWM5CON= 0b11000000; // PWM5 enable PWM5CONbits.PWM5EN = 1 (bit7), Active High (bit4:PWM5POL=0)
    PWM5CON= 0b00000000; // PWM5 enable PWM5CONbits.PWM5EN = 1 (bit7), Active High (bit4:PWM5POL=0)
    PWM5DCH= 60;
}

void IR_Send(uint16_t data) {
    PWM5CONbits.PWM5EN = 1;
    __delay_us(T_US * 4);
     for (int i = 11; i >= 0; i--) {
        int bit = (data >> i) & 1;
        if(bit){
            PWM5CONbits.PWM5EN = 0;
            __delay_us(T_US);
            PWM5CONbits.PWM5EN = 1;
            __delay_us(T_US * 2);
        } else {
            PWM5CONbits.PWM5EN = 0;
            __delay_us(T_US);
            PWM5CONbits.PWM5EN = 1;
            __delay_us(T_US);
        }
    }
    PWM5CONbits.PWM5EN = 0;
}