#define F_CPU 16000000UL
#include <avr/io.h>
#include <util/delay.h>

// DHT11 connection - connect to PORTD pin 2 (PD2)
#define DHT11_PIN PD2
#define DHT11_PORT PORTD
#define DHT11_DDR DDRD
#define DHT11_PIN_IN PIND

// Function prototypes
uint8_t dht11_read(uint8_t* temperature, uint8_t* humidity);
static uint8_t read_dht11_byte(void);

uint8_t dht11_read(uint8_t* temperature, uint8_t* humidity) {
    uint8_t data[5] = {0, 0, 0, 0, 0};
    uint8_t i, checksum;
    
    // Initial state
    DHT11_DDR |= (1 << DHT11_PIN);  // Set as output
    DHT11_PORT |= (1 << DHT11_PIN); // Pull high
    _delay_ms(100);  // Wait for sensor to stabilize
    
    // Send start signal
    DHT11_PORT &= ~(1 << DHT11_PIN); // Pull low
    _delay_ms(18);  // Wait at least 18ms
    DHT11_PORT |= (1 << DHT11_PIN);  // Pull high
    _delay_us(40);  // Wait 20-40us
    
    // Set as input to read data
    DHT11_DDR &= ~(1 << DHT11_PIN);
    
    // Check sensor response
    if ((DHT11_PIN_IN & (1 << DHT11_PIN))) {
        return 1;  // Sensor not responding
    }
    _delay_us(80); // Wait for sensor response
    
    if (!(DHT11_PIN_IN & (1 << DHT11_PIN))) {
        return 1;  // Sensor not responding
    }
    _delay_us(80);
    
    // Read 40 bits (5 bytes)
    for (i = 0; i < 5; i++) {
        data[i] = read_dht11_byte();
    }
    
    // Verify checksum
    checksum = data[0] + data[1] + data[2] + data[3];
    if (checksum != data[4]) {
        return 1;  // Checksum error
    }
    
    *humidity = data[0];      // Integer part of humidity
    *temperature = data[2];   // Integer part of temperature
    
    return 0;  // Success
}

static uint8_t read_dht11_byte(void) {
    uint8_t i, result = 0;
    
    for (i = 0; i < 8; i++) {
        // Wait for pin to go high
        while (!(DHT11_PIN_IN & (1 << DHT11_PIN)));
        _delay_us(30);
        
        // Check if bit is 1 or 0
        if (DHT11_PIN_IN & (1 << DHT11_PIN)) {
            result |= (1 << (7 - i));
        }
        
        // Wait for pin to go low
        while (DHT11_PIN_IN & (1 << DHT11_PIN));
    }
    
    return result;
    Serial.print(": result");
}

int main(void) {
    uint8_t temperature, humidity;
    Serial.begin(9600); 
    // Initialize ports
    DHT11_DDR |= (1 << DHT11_PIN);   // Set as output initially
    DHT11_PORT |= (1 << DHT11_PIN);  // Pull high
    
    while (1) {
        if (dht11_read(&temperature, &humidity) == 0) {
            // Data read successfully
            // Add your code here to use temperature and humidity values
            // For example, send to UART or display on LCD
        }
        
        _delay_ms(2000);  // Wait 2 seconds before next reading
    }
    
    return 0;
}