PIC16f877-DS18b20-DS18B20SensorFunctions

// Start DS18B20 communication and check response
unsigned char ds18b20_start(void) {
    unsigned char response;
    
    DS18B20_TRIS = 0;      // Set as output
    DS18B20_PIN = 0;       // Send reset pulse
    __delay_us(500);       // Hold for 500us
    
    DS18B20_TRIS = 1;      // Set as input
    __delay_us(100);       // Wait for response
    
    response = DS18B20_PIN; // Read response
    __delay_us(400);        // Wait 400us
    
    return !response;       // Return TRUE if sensor detected
}

// Write a single bit to DS18B20
void ds18b20_write_bit(unsigned char bit) {
    DS18B20_TRIS = 0;      // Set as output
    DS18B20_PIN = 0;       // Pull low
    __delay_us(2);
    
    if(bit) DS18B20_PIN = 1;  // Send bit
    __delay_us(80);        // Hold for 80us
    
    DS18B20_TRIS = 1;      // Release line
    __delay_us(2);
}

// Write a byte to DS18B20
void ds18b20_write_byte(unsigned char byte) {
    for(unsigned char i = 0; i < 8; i++) {
        ds18b20_write_bit(byte & 0x01);
        byte >>= 1;
    }
}

// Read a single bit from DS18B20
unsigned char ds18b20_read_bit(void) {
    unsigned char bit;
    
    DS18B20_TRIS = 0;      // Set as output
    DS18B20_PIN = 0;       // Pull low
    __delay_us(2);
    
    DS18B20_TRIS = 1;      // Release line
    __delay_us(5);         // Wait 5us
    
    bit = DS18B20_PIN;     // Read bit
    __delay_us(100);       // Wait 100us
    
    return bit;
}

// Read a byte from DS18B20
unsigned char ds18b20_read_byte(void) {
    unsigned char byte = 0;
    for(unsigned char i = 0; i < 8; i++) {
        byte >>= 1;
        if(ds18b20_read_bit()) byte |= 0x80;
    }
    return byte;
}

// Read temperature from DS18B20
unsigned char ds18b20_read(signed int *raw_temp_value) {
    unsigned char temp_l, temp_h;
    
    if(!ds18b20_start()) return 0;
    
    ds18b20_write_byte(0xCC);  // Skip ROM command
    ds18b20_write_byte(0x44);  // Start conversion
    
    while(!ds18b20_read_byte());  // Wait for conversion
    
    if(!ds18b20_start()) return 0;
    
    ds18b20_write_byte(0xCC);  // Skip ROM command
    ds18b20_write_byte(0xBE);  // Read scratchpad
    
    temp_l = ds18b20_read_byte();  // LSB
    temp_h = ds18b20_read_byte();  // MSB
    
    *raw_temp_value = (temp_h << 8) | temp_l;
    
    return 1;
}