/* 
 * File:   main.c
 * Author: clement
 *
 * Created on July 14, 2025, 3:54 PM
 */

#include <stdio.h>
#include <stdlib.h>
#include <xc.h>

// Configuration bits
#pragma config FOSC = INTOSC    // Oscillator Selection bits (INTOSC oscillator: I/O function on CLKIN pin)
#pragma config WDTE = OFF       // Watchdog Timer Enable (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable (PWRT disabled)
#pragma config MCLRE = ON       // MCLR Pin Function Select (MCLR/VPP pin function is digital input)
#pragma config CP = OFF         // Flash Program Memory Code Protection (Program memory code protection is disabled)
#pragma config BOREN = OFF      // Brown-out Reset Enable (Brown-out Reset disabled)
#pragma config CLKOUTEN = OFF   // Clock Out Enable (CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin)
#pragma config LVP = OFF
#pragma config DEBUG = ON
#pragma config PLLEN = 0

// Pins define
#define DHT22_PIN_DIR TRISAbits.TRISA4
#define DHT22_DATA PORTAbits.RA4
#define CTRL_1 PORTAbits.RA5
#define CTRL_2 PORTAbits.RA2

// Clock frequency (used for __delay_xx)
#define _XTAL_FREQ 8000000

// Utils macro for waiting a pin state for DHT22_DATA, returning 1 if timed out.
#define waitDHTOrRet(up) TMR0 = 0; while(DHT22_DATA != (up)){ if(TMR0 > 240) return 1; }

uint8_t dhtBytes[5]; // 2 first bytes: humidity, 2 following: temperature, 5th: checksum
// Reads the DHT, returns 0 if error
int readDHT() {
    // Empty old payload
    for(uint8_t i = 0; i < 5; i++){
        dhtBytes[i] = 0;
    }
    
    // Wait for an old payload eventually aborted to end (lasts about 4ms)
    __delay_ms(5);

    // Sends the start signal: low for at least 1ms, then high for 20 to 40us
    DHT22_PIN_DIR = 0; // configure as output, then set it as 0 (= LATAbits.LATA4).
    __delay_ms(2);
    DHT22_PIN_DIR = 1; // configure as input, then set it as 1 (through pullup).
    __delay_us(40);
    
    // Check DHT start response
    waitDHTOrRet(0); // DHT pulls low
    waitDHTOrRet(1); // DHT pulls high for 80ms
    __delay_us(40);
    waitDHTOrRet(0); // DHT pulls low
                
    // Read the 5 DHT payload bytes in dhtBytes
    for (uint8_t n = 0; n < 5; n++) {
        for (int8_t i = 7; i >= 0; i--) {
            waitDHTOrRet(1); // Wait for up
            CTRL_1 = 1;
            waitDHTOrRet(0); // Wait for low. Waited time is TMR0.
            CTRL_1 = 0;

            if (TMR0 > 50) { // Low: 26-28us  High: 70us
                dhtBytes[n] |= 1 << i;
            }
        }
    }
    return 0;
}
// Fetches humidity & temp from DHT, returns 0 if error
int fetchClimate(int8_t* humidity, int8_t* temperature) {
    if(readDHT()) return 1;
    
    uint8_t checksum = dhtBytes[0] + dhtBytes[1] + dhtBytes[2] + dhtBytes[3];
    if (dhtBytes[4] != checksum) {
        return 1; // Checksum error
    }
    
    uint16_t hum = (((uint16_t) (dhtBytes[0])) << 8) | ((uint16_t) dhtBytes[1]);
    *humidity = (int8_t) (hum / 10);

    uint16_t temp = (((uint16_t) (dhtBytes[2])) << 8) | ((uint16_t) dhtBytes[3]);
    int8_t tempRound = (temp % 10) >= 5 ? 1 : 0;
    if (temp & 0x8000) { // If high bit is 1, temperature is negative.
        *temperature = - (int8_t) ((temp & 0x7FFF) / 10) - tempRound;
    }else {
        *temperature = (int8_t) (temp / 10) + tempRound;
    }
    
    
    return 0;
}

void main() {
    // 8MHz internal clock
    OSCCON = 0b01110000;
    
    // Ping config
    TRISA  = 0b11011011; // Declare RA2 and RA5 as output (bit = 0)
    ANSELA = 0b00000011; // Declare used pins as digital I/O (bit = 0)
    WPUA = 0b00010000; // Active la résistance de pull-up sur RA4
    LATAbits.LATA4 = 0; // Declare RA4 output value as 0 (only effective when DHT22_PIN_DIR = 0)

    // Timer 0 config
    OPTION_REGbits.PSA = 0; // Enable prescaler
    OPTION_REGbits.PS = 0b000; // 1/2 prescaler
    OPTION_REGbits.TMR0CS = 0; // Use internal clock
    OPTION_REGbits.TMR0SE = 0; // Increment on rising edge
    
    
    while (1) {
        int8_t hum = 0;
        int8_t temp = 0;
        
        int is_error = fetchClimate(&hum, &temp);
        if(is_error){
            __delay_ms(5000);
        }
        __delay_ms(200);
    }
}