ardupilot/libraries/AP_TemperatureSensor/AP_TemperatureSensor_MLX90614.cpp

#include "AP_TemperatureSensor_config.h"

#if AP_TEMPERATURE_SENSOR_MLX90614_ENABLED

#include "AP_TemperatureSensor_MLX90614.h"

#include <AP_HAL/AP_HAL.h>
#include <AP_HAL/I2CDevice.h>
#include <AP_Math/AP_Math.h>


extern const AP_HAL::HAL &hal;

#define MLX90614_I2CDEFAULTADDR 0x5A    // Device default slave address 
#define MLX90614_BROADCASTADDR  0       // Device broadcast slave address 

//  RAM addresses
#define MLX90614_RAWIR1         0x04    //  RAM reg - Raw temperature, source #1 
#define MLX90614_RAWIR2         0x05    //  RAM reg - Raw temperature, source #2 
#define MLX90614_TA             0x06    //  RAM reg - Linearized temperature, ambient 
#define MLX90614_TOBJ1          0x07    //  RAM reg - Linearized temperature, source #1 
#define MLX90614_TOBJ2          0x08    //  RAM reg - Linearized temperature, source #2 

void AP_TemperatureSensor_MLX90614::init()
{
    _params.bus_address.set_default(MLX90614_I2CDEFAULTADDR);
    
    _dev = std::move(hal.i2c_mgr->get_device(_params.bus, _params.bus_address));
    if (!_dev) {
        return;
    }

    WITH_SEMAPHORE(_dev->get_semaphore());

    _dev->register_periodic_callback(50 * AP_USEC_PER_MSEC,
                                     FUNCTOR_BIND_MEMBER(&AP_TemperatureSensor_MLX90614::_timer, void));
}


void AP_TemperatureSensor_MLX90614::_timer()
{
    const uint16_t _crude_value = read_data(MLX90614_TA);
    
    if (_crude_value == 0) {
        return;
    }

    WITH_SEMAPHORE(_dev->get_semaphore());
        
    // temp * 0.02 - 273.15 = degrees, temp * 0.02 is temperature in kelvin
    const float tmp = KELVIN_TO_C(_crude_value * 0.02);
    set_temperature(tmp);
}



uint16_t AP_TemperatureSensor_MLX90614::read_data(uint8_t cmd)
{
    uint8_t val[3];
  
    if (!_dev->transfer(&cmd, 1, val, 3)) {
        return 0;
    }
    return UINT16_VALUE(val[1],val[0]);
}
#endif // AP_TEMPERATURE_SENSOR_MLX90614_ENABLED