File content as of revision 4:d32eaca53504:

/*!
LTC2945: 12-Bit Wide Range Power Monitor

@verbatim

The LTC2945 is a rail-to-rail system monitor that measures current, voltage, and
power. It features an operating range of 2.7V to 80V and includes a shunt
regulator for supplies above 80V to allow flexibility in the selection of input
supply. The current measurement range of 0V to 80V is independent of the input
supply. An onboard 0.75% accurate 12-bit ADC measures load current, input
voltage and an auxiliary external voltage. A 24-bit power value is generated by
digitally multiplying the measured 12-bit load current and input voltage data.
Minimum and maximum values are stored and an overrange alert with programmable
thresholds minimizes the need for software polling. Data is reported via a
standard I2C interface. Shutdown mode reduces power consumption to 20uA.

@endverbatim

http://www.linear.com/product/LTC2945

http://www.linear.com/product/ltc2945#demoboards

REVISION HISTORY
$Revision: 6237 $
$Date: 2016-12-20 15:09:16 -0800 (Tue, 20 Dec 2016) $

Copyright (c) 2013, Linear Technology Corp.(LTC)
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

The views and conclusions contained in the software and documentation are those
of the authors and should not be interpreted as representing official policies,
either expressed or implied, of Linear Technology Corp.

The Linear Technology Linduino is not affiliated with the official Arduino team.
However, the Linduino is only possible because of the Arduino team's commitment
to the open-source community.  Please, visit http://www.arduino.cc and
http://store.arduino.cc , and consider a purchase that will help fund their
ongoing work.
*/

//! @ingroup Power_Monitors
//! @{
//! @defgroup LTC2945 LTC2945: 12-Bit Wide Range Power Monitor
//! @}

/*! @file
   @ingroup LTC2945
   Library for LTC2945 12-Bit Wide Range Power Monitor
*/

#include "LT_I2C.h"
#include "LTC2945.h"

/* compatibility definitions */

#define i2c_start                       lt_i2c_start
#define i2c_stop                        lt_i2c_stop
#define i2c_write                       lt_i2c_write
#define i2c_write_byte_data             lt_i2c_write_byte_data
#define i2c_write_word_data             lt_i2c_write_word_data
#define i2c_write_block_data            lt_i2c_write_block_data
#define i2c_read                        lt_i2c_read
#define i2c_read_byte_data              lt_i2c_read_byte_data
#define i2c_read_word_data              lt_i2c_read_word_data
#define i2c_read_block_data             lt_i2c_read_block_data

/* definitions in Linduino.h, that doesn't exist here */
//! @todo Make a note about whether Arduino/Linduino is Big Endian or Little Endian. Raspberry Pi appears to be the opposite.
//! This union splits one int32_t (32-bit signed integer) or uint32_t (32-bit unsigned integer)
//! into four uint8_t's (8-bit unsigned integers) and vice versa.
union LT_union_int32_4bytes
{
  int32_t LT_int32;    //!< 32-bit signed integer to be converted to four bytes
  uint32_t LT_uint32;  //!< 32-bit unsigned integer to be converted to four bytes
  uint8_t LT_byte[4];  //!< 4 bytes (unsigned 8-bit integers) to be converted to a 32-bit signed or unsigned integer
};

// Write an 8-bit code to the LTC2945.
int8_t LTC2945_write(uint8_t i2c_address, uint8_t adc_command, uint8_t code)
// The function returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
{
  int32_t ack;

  ack = i2c_write_byte_data(i2c_address, adc_command, code);

  return ack;

}

// Write a 16-bit code to the LTC2945.
int8_t LTC2945_write_16_bits(uint8_t i2c_address, uint8_t adc_command, uint16_t code)
// The function returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
{
  int8_t ack;

  ack = i2c_write_word_data(i2c_address, adc_command, code);
  return(ack);
}

// Write a 24-bit code to the LTC2945.
int8_t LTC2945_write_24_bits(uint8_t i2c_address, uint8_t adc_command, int32_t code)
// The function returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
{
  int8_t ack;

  LT_union_int32_4bytes data;
  data.LT_int32 = code;

  ack = i2c_write_block_data(i2c_address, adc_command, (uint8_t) 3, data.LT_byte);

  return(ack);
}

// Reads an 8-bit adc_code from LTC2945
int8_t LTC2945_read(uint8_t i2c_address, uint8_t adc_command, uint8_t *adc_code)
// The function returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
{
  int32_t ack;

  ack = i2c_read_byte_data(i2c_address, adc_command, adc_code);

  return ack;
}

// Reads a 12-bit adc_code from LTC2945
int8_t LTC2945_read_12_bits(uint8_t i2c_address, uint8_t adc_command, uint16_t *adc_code)
// The function returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
{
  // Use union type defined in Linduino.h to combine two uint8_t's (8-bit unsigned integers) into one uint16_t (unsigned 16-bit integer)
  // Then, shift by 4 bits and return in *adc_code
  int32_t ack;

  ack = i2c_read_word_data(i2c_address, adc_command, adc_code);

  *adc_code >>= 4;
  return ack;
}

// Reads a 16-bit adc_code from LTC2945
int8_t LTC2945_read_16_bits(uint8_t i2c_address, uint8_t adc_command, uint16_t *adc_code)
// The function returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
{
  int32_t ack;

  ack = i2c_read_word_data(i2c_address, adc_command, adc_code);

  return ack;
}

// Reads a 24-bit adc_code from LTC2945
int8_t LTC2945_read_24_bits(uint8_t i2c_address, uint8_t adc_command, int32_t *adc_code)
// The function returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
{
  int8_t ack;

  LT_union_int32_4bytes data;

  ack = i2c_read_block_data(i2c_address, adc_command, (uint8_t)3, data.LT_byte);

  *adc_code = 0x0FFFFFF & data.LT_int32;
  return(ack);
}

// Calculate the LTC2945 VIN voltage
float LTC2945_VIN_code_to_voltage(uint16_t adc_code, float LTC2945_VIN_lsb)
// Returns the VIN Voltage in Volts
{
  float voltage;
  voltage = (float)adc_code*LTC2945_VIN_lsb;    //! 1) Calculate voltage from code and lsb
  return(voltage);
}

// Calculate the LTC2945 ADIN voltage
float LTC2945_ADIN_code_to_voltage(uint16_t adc_code, float LTC2945_ADIN_lsb)
// Returns the ADIN Voltage in Volts
{
  float adc_voltage;
  adc_voltage = (float)adc_code*LTC2945_ADIN_lsb;   //! 1) Calculate voltage from code and ADIN lsb
  return(adc_voltage);
}

// Calculate the LTC2945 current with a sense resistor
float LTC2945_code_to_current(uint16_t adc_code, float resistor, float LTC2945_DELTA_SENSE_lsb)
// Returns the LTC2945 current
{
  float voltage, current;
  voltage = (float)adc_code*LTC2945_DELTA_SENSE_lsb;    //! 1) Calculate voltage from ADC code and delta sense lsb
  current = voltage/resistor;                           //! 2) Calculate current, I = V/R
  return(current);
}

// Calculate the LTC2945 power
float LTC2945_code_to_power(int32_t adc_code, float resistor, float LTC2945_Power_lsb)
// Returns The LTC2945 power
{
  float voltage, power;
  voltage = (float)adc_code*LTC2945_Power_lsb;  //! 1) Calculate V^2 from ADC code and power lsb
  power = voltage/resistor;                     //! 2) Calculate Power, P = V^2/R
  return(power);
}

// Calculate the LTC2945 power with the ADIN
float LTC2945_code_to_ADIN_power(int32_t adc_code, float resistor, float LTC2945_ADIN_DELTA_SENSE_lsb)
// Returns the LTC2945 power with the ADIN
{
  float voltage, power;
  voltage=(float)adc_code*LTC2945_ADIN_DELTA_SENSE_lsb;   //! 1) Calculate V^2 from ADC code and ADIN delta sense lsb
  power = voltage/resistor;                               //! 2) Calculate Power, P = V^2/R
  return(power);
}