File content as of revision 32:0a09505a656d:

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#include <I2C.h>
#include "MAX44009.hpp"

static const int I2C_OK = 0;

MAX44009::MAX44009(mbed::I2C & I2C_interface, uint8_t I2C_address)
    : m_I2C_interface(I2C_interface), m_I2C_address(I2C_address) {}

MAX44009::Result MAX44009::read_current_lux(double & lux) const {
  uint8_t I2C_data, mantissa, exponent;

  I2C_data = Lux_High_Byte_Reg;
  if (m_I2C_interface.write(m_I2C_address, reinterpret_cast<char *>(&I2C_data),
                            1, true) != I2C_OK) {
    m_I2C_interface.stop();
    return Hardware_Failure;
  }
  if (m_I2C_interface.read(m_I2C_address, reinterpret_cast<char *>(&I2C_data),
                           1, true) != I2C_OK) {
    m_I2C_interface.stop();
    return Hardware_Failure;
  }
  mantissa = (I2C_data << 4);
  exponent = (I2C_data >> 4);

  I2C_data = Lux_Low_Byte_Reg;
  if (m_I2C_interface.write(m_I2C_address, reinterpret_cast<char *>(&I2C_data),
                            1, true) != I2C_OK) {
    m_I2C_interface.stop();
    return Hardware_Failure;
  }
  if (m_I2C_interface.read(m_I2C_address, reinterpret_cast<char *>(&I2C_data),
                           1, false) != I2C_OK) {
    m_I2C_interface.stop();
    return Hardware_Failure;
  }
  mantissa |= (I2C_data & 0x0F);

  unsigned long calc_result = 1;
  if (exponent > 0) {
    calc_result <<= exponent;
  }
  calc_result *= mantissa;
  lux = calc_result * 0.045;

  return Success;
}