Adafruit_INA219.cpp

/*!
 * @file Adafruit_INA219.cpp
 *
 * @mainpage Adafruit INA219 current/power monitor IC
 *
 * @section intro_sec Introduction
 *
 *  Driver for the INA219 current sensor
 *
 *  This is a library for the Adafruit INA219 breakout
 *  ----> https://www.adafruit.com/products/904
 *
 *  Adafruit invests time and resources providing this open source code,
 *  please support Adafruit and open-source hardware by purchasing
 *  products from Adafruit!
 *
 * @section author Author
 *
 * Written by Kevin "KTOWN" Townsend for Adafruit Industries.
 *
 * @section license License
 *
 * BSD license, all text here must be included in any redistribution.
 *
 */

#if ARDUINO >= 100
 #include "Arduino.h"
#else
 #include "WProgram.h"
#endif

#include <Wire.h>

#include "Adafruit_INA219.h"

/**************************************************************************/
/*!
    @brief  Sends a single command byte over I2C
*/
/**************************************************************************/
void Adafruit_INA219::wireWriteRegister (uint8_t reg, uint16_t value)
{
  _i2c->beginTransmission(ina219_i2caddr);
  #if ARDUINO >= 100
    _i2c->write(reg);                       // Register
    _i2c->write((value >> 8) & 0xFF);       // Upper 8-bits
    _i2c->write(value & 0xFF);              // Lower 8-bits
  #else
    _i2c->send(reg);                        // Register
    _i2c->send(value >> 8);                 // Upper 8-bits
    _i2c->send(value & 0xFF);               // Lower 8-bits
  #endif
  _i2c->endTransmission();
}

/**************************************************************************/
/*!
    @brief  Reads a 16 bit values over I2C
*/
/**************************************************************************/
void Adafruit_INA219::wireReadRegister(uint8_t reg, uint16_t *value)
{

  _i2c->beginTransmission(ina219_i2caddr);
  #if ARDUINO >= 100
    _i2c->write(reg);                       // Register
  #else
    _i2c->send(reg);                        // Register
  #endif
  _i2c->endTransmission();

  delay(1); // Max 12-bit conversion time is 586us per sample

  _i2c->requestFrom(ina219_i2caddr, (uint8_t)2);
  #if ARDUINO >= 100
    // Shift values to create properly formed integer
    *value = ((_i2c->read() << 8) | _i2c->read());
  #else
    // Shift values to create properly formed integer
    *value = ((_i2c->receive() << 8) | _i2c->receive());
  #endif
}

/**************************************************************************/
/*!
    @brief  Configures to INA219 to be able to measure up to 32V and 2A
            of current.  Each unit of current corresponds to 100uA, and
            each unit of power corresponds to 2mW. Counter overflow
            occurs at 3.2A.

    @note   These calculations assume a 0.1 ohm resistor is present
*/
/**************************************************************************/
void Adafruit_INA219::setCalibration_32V_2A(void)
{
  // By default we use a pretty huge range for the input voltage,
  // which probably isn't the most appropriate choice for system
  // that don't use a lot of power.  But all of the calculations
  // are shown below if you want to change the settings.  You will
  // also need to change any relevant register settings, such as
  // setting the VBUS_MAX to 16V instead of 32V, etc.

  // VBUS_MAX = 32V             (Assumes 32V, can also be set to 16V)
  // VSHUNT_MAX = 0.32          (Assumes Gain 8, 320mV, can also be 0.16, 0.08, 0.04)
  // RSHUNT = 0.1               (Resistor value in ohms)

  // 1. Determine max possible current
  // MaxPossible_I = VSHUNT_MAX / RSHUNT
  // MaxPossible_I = 3.2A

  // 2. Determine max expected current
  // MaxExpected_I = 2.0A

  // 3. Calculate possible range of LSBs (Min = 15-bit, Max = 12-bit)
  // MinimumLSB = MaxExpected_I/32767
  // MinimumLSB = 0.000061              (61uA per bit)
  // MaximumLSB = MaxExpected_I/4096
  // MaximumLSB = 0,000488              (488uA per bit)

  // 4. Choose an LSB between the min and max values
  //    (Preferrably a roundish number close to MinLSB)
  // CurrentLSB = 0.0001 (100uA per bit)

  // 5. Compute the calibration register
  // Cal = trunc (0.04096 / (Current_LSB * RSHUNT))
  // Cal = 4096 (0x1000)

  ina219_calValue = 4096;

  // 6. Calculate the power LSB
  // PowerLSB = 20 * CurrentLSB
  // PowerLSB = 0.002 (2mW per bit)

  // 7. Compute the maximum current and shunt voltage values before overflow
  //
  // Max_Current = Current_LSB * 32767
  // Max_Current = 3.2767A before overflow
  //
  // If Max_Current > Max_Possible_I then
  //    Max_Current_Before_Overflow = MaxPossible_I
  // Else
  //    Max_Current_Before_Overflow = Max_Current
  // End If
  //
  // Max_ShuntVoltage = Max_Current_Before_Overflow * RSHUNT
  // Max_ShuntVoltage = 0.32V
  //
  // If Max_ShuntVoltage >= VSHUNT_MAX
  //    Max_ShuntVoltage_Before_Overflow = VSHUNT_MAX
  // Else
  //    Max_ShuntVoltage_Before_Overflow = Max_ShuntVoltage
  // End If

  // 8. Compute the Maximum Power
  // MaximumPower = Max_Current_Before_Overflow * VBUS_MAX
  // MaximumPower = 3.2 * 32V
  // MaximumPower = 102.4W

  // Set multipliers to convert raw current/power values
  ina219_currentDivider_mA = 10;  // Current LSB = 100uA per bit (1000/100 = 10)
  ina219_powerMultiplier_mW = 2;     // Power LSB = 1mW per bit (2/1)

  // Set Calibration register to 'Cal' calculated above
  wireWriteRegister(INA219_REG_CALIBRATION, ina219_calValue);

  // Set Config register to take into account the settings above
  uint16_t config = INA219_CONFIG_BVOLTAGERANGE_32V |
                    INA219_CONFIG_GAIN_8_320MV |
                    INA219_CONFIG_BADCRES_12BIT |
                    INA219_CONFIG_SADCRES_12BIT_1S_532US |
                    INA219_CONFIG_MODE_SANDBVOLT_CONTINUOUS;
  wireWriteRegister(INA219_REG_CONFIG, config);
}

/**************************************************************************/
/*!
    @brief  Configures to INA219 to be able to measure up to 32V and 1A
            of current.  Each unit of current corresponds to 40uA, and each
            unit of power corresponds to 800�W. Counter overflow occurs at
            1.3A.

    @note   These calculations assume a 0.1 ohm resistor is present
*/
/**************************************************************************/
void Adafruit_INA219::setCalibration_32V_1A(void)
{
  // By default we use a pretty huge range for the input voltage,
  // which probably isn't the most appropriate choice for system
  // that don't use a lot of power.  But all of the calculations
  // are shown below if you want to change the settings.  You will
  // also need to change any relevant register settings, such as
  // setting the VBUS_MAX to 16V instead of 32V, etc.

  // VBUS_MAX = 32V		(Assumes 32V, can also be set to 16V)
  // VSHUNT_MAX = 0.32	(Assumes Gain 8, 320mV, can also be 0.16, 0.08, 0.04)
  // RSHUNT = 0.1			(Resistor value in ohms)

  // 1. Determine max possible current
  // MaxPossible_I = VSHUNT_MAX / RSHUNT
  // MaxPossible_I = 3.2A

  // 2. Determine max expected current
  // MaxExpected_I = 1.0A

  // 3. Calculate possible range of LSBs (Min = 15-bit, Max = 12-bit)
  // MinimumLSB = MaxExpected_I/32767
  // MinimumLSB = 0.0000305             (30.5�A per bit)
  // MaximumLSB = MaxExpected_I/4096
  // MaximumLSB = 0.000244              (244�A per bit)

  // 4. Choose an LSB between the min and max values
  //    (Preferrably a roundish number close to MinLSB)
  // CurrentLSB = 0.0000400 (40�A per bit)

  // 5. Compute the calibration register
  // Cal = trunc (0.04096 / (Current_LSB * RSHUNT))
  // Cal = 10240 (0x2800)

  ina219_calValue = 10240;

  // 6. Calculate the power LSB
  // PowerLSB = 20 * CurrentLSB
  // PowerLSB = 0.0008 (800�W per bit)

  // 7. Compute the maximum current and shunt voltage values before overflow
  //
  // Max_Current = Current_LSB * 32767
  // Max_Current = 1.31068A before overflow
  //
  // If Max_Current > Max_Possible_I then
  //    Max_Current_Before_Overflow = MaxPossible_I
  // Else
  //    Max_Current_Before_Overflow = Max_Current
  // End If
  //
  // ... In this case, we're good though since Max_Current is less than MaxPossible_I
  //
  // Max_ShuntVoltage = Max_Current_Before_Overflow * RSHUNT
  // Max_ShuntVoltage = 0.131068V
  //
  // If Max_ShuntVoltage >= VSHUNT_MAX
  //    Max_ShuntVoltage_Before_Overflow = VSHUNT_MAX
  // Else
  //    Max_ShuntVoltage_Before_Overflow = Max_ShuntVoltage
  // End If

  // 8. Compute the Maximum Power
  // MaximumPower = Max_Current_Before_Overflow * VBUS_MAX
  // MaximumPower = 1.31068 * 32V
  // MaximumPower = 41.94176W

  // Set multipliers to convert raw current/power values
  ina219_currentDivider_mA = 25;      // Current LSB = 40uA per bit (1000/40 = 25)
  ina219_powerMultiplier_mW = 0.8f;   // Power LSB = 800uW per bit

  // Set Calibration register to 'Cal' calculated above
  wireWriteRegister(INA219_REG_CALIBRATION, ina219_calValue);

  // Set Config register to take into account the settings above
  uint16_t config = INA219_CONFIG_BVOLTAGERANGE_32V |
                    INA219_CONFIG_GAIN_8_320MV |
                    INA219_CONFIG_BADCRES_12BIT |
                    INA219_CONFIG_SADCRES_12BIT_1S_532US |
                    INA219_CONFIG_MODE_SANDBVOLT_CONTINUOUS;
  wireWriteRegister(INA219_REG_CONFIG, config);
}

/**************************************************************************/
/*!
    @brief set device to alibration which uses the highest precision for
      current measurement (0.1mA), at the expense of
      only supporting 16V at 400mA max.
*/
/**************************************************************************/
void Adafruit_INA219::setCalibration_16V_400mA(void) {

  // Calibration which uses the highest precision for
  // current measurement (0.1mA), at the expense of
  // only supporting 16V at 400mA max.

  // VBUS_MAX = 16V
  // VSHUNT_MAX = 0.04          (Assumes Gain 1, 40mV)
  // RSHUNT = 0.1               (Resistor value in ohms)

  // 1. Determine max possible current
  // MaxPossible_I = VSHUNT_MAX / RSHUNT
  // MaxPossible_I = 0.4A

  // 2. Determine max expected current
  // MaxExpected_I = 0.4A

  // 3. Calculate possible range of LSBs (Min = 15-bit, Max = 12-bit)
  // MinimumLSB = MaxExpected_I/32767
  // MinimumLSB = 0.0000122              (12uA per bit)
  // MaximumLSB = MaxExpected_I/4096
  // MaximumLSB = 0.0000977              (98uA per bit)

  // 4. Choose an LSB between the min and max values
  //    (Preferrably a roundish number close to MinLSB)
  // CurrentLSB = 0.00005 (50uA per bit)

  // 5. Compute the calibration register
  // Cal = trunc (0.04096 / (Current_LSB * RSHUNT))
  // Cal = 8192 (0x2000)

  ina219_calValue = 8192;

  // 6. Calculate the power LSB
  // PowerLSB = 20 * CurrentLSB
  // PowerLSB = 0.001 (1mW per bit)

  // 7. Compute the maximum current and shunt voltage values before overflow
  //
  // Max_Current = Current_LSB * 32767
  // Max_Current = 1.63835A before overflow
  //
  // If Max_Current > Max_Possible_I then
  //    Max_Current_Before_Overflow = MaxPossible_I
  // Else
  //    Max_Current_Before_Overflow = Max_Current
  // End If
  //
  // Max_Current_Before_Overflow = MaxPossible_I
  // Max_Current_Before_Overflow = 0.4
  //
  // Max_ShuntVoltage = Max_Current_Before_Overflow * RSHUNT
  // Max_ShuntVoltage = 0.04V
  //
  // If Max_ShuntVoltage >= VSHUNT_MAX
  //    Max_ShuntVoltage_Before_Overflow = VSHUNT_MAX
  // Else
  //    Max_ShuntVoltage_Before_Overflow = Max_ShuntVoltage
  // End If
  //
  // Max_ShuntVoltage_Before_Overflow = VSHUNT_MAX
  // Max_ShuntVoltage_Before_Overflow = 0.04V

  // 8. Compute the Maximum Power
  // MaximumPower = Max_Current_Before_Overflow * VBUS_MAX
  // MaximumPower = 0.4 * 16V
  // MaximumPower = 6.4W

  // Set multipliers to convert raw current/power values
  ina219_currentDivider_mA = 20;    // Current LSB = 50uA per bit (1000/50 = 20)
  ina219_powerMultiplier_mW = 1.0f; // Power LSB = 1mW per bit

  // Set Calibration register to 'Cal' calculated above
  wireWriteRegister(INA219_REG_CALIBRATION, ina219_calValue);

  // Set Config register to take into account the settings above
  uint16_t config = INA219_CONFIG_BVOLTAGERANGE_16V |
                    INA219_CONFIG_GAIN_1_40MV |
                    INA219_CONFIG_BADCRES_12BIT |
                    INA219_CONFIG_SADCRES_12BIT_1S_532US |
                    INA219_CONFIG_MODE_SANDBVOLT_CONTINUOUS;
  wireWriteRegister(INA219_REG_CONFIG, config);
}

/**************************************************************************/
/*!
    @brief  Instantiates a new INA219 class
    @param addr the I2C address the device can be found on. Default is 0x40
*/
/**************************************************************************/
Adafruit_INA219::Adafruit_INA219(uint8_t addr) {
  ina219_i2caddr = addr;
  ina219_currentDivider_mA = 0;
  ina219_powerMultiplier_mW = 0.0f;
}

/**************************************************************************/
/*!
    @brief  Setups the HW (defaults to 32V and 2A for calibration values)
    @param theWire the TwoWire object to use
*/
/**************************************************************************/
void Adafruit_INA219::begin(TwoWire *theWire) {
  _i2c = theWire;
  init();
}

/**************************************************************************/
/*!
    @brief  Setups the HW using the default Wire object
*/
/**************************************************************************/
void Adafruit_INA219::begin(void) {
  _i2c = &Wire;
  init();
}

/**************************************************************************/
/*!
    @brief  begin I2C and set up the hardware
*/
/**************************************************************************/
void Adafruit_INA219::init() {
  _i2c->begin();
  // Set chip to large range config values to start
  setCalibration_32V_2A();
}

/**************************************************************************/
/*!
    @brief  Gets the raw bus voltage (16-bit signed integer, so +-32767)
    @return the raw bus voltage reading
*/
/**************************************************************************/
int16_t Adafruit_INA219::getBusVoltage_raw() {
  uint16_t value;
  wireReadRegister(INA219_REG_BUSVOLTAGE, &value);

  // Shift to the right 3 to drop CNVR and OVF and multiply by LSB
  return (int16_t)((value >> 3) * 4);
}

/**************************************************************************/
/*!
    @brief  Gets the raw shunt voltage (16-bit signed integer, so +-32767)
    @return the raw shunt voltage reading
*/
/**************************************************************************/
int16_t Adafruit_INA219::getShuntVoltage_raw() {
  uint16_t value;
  wireReadRegister(INA219_REG_SHUNTVOLTAGE, &value);
  return (int16_t)value;
}

/**************************************************************************/
/*!
    @brief  Gets the raw current value (16-bit signed integer, so +-32767)
    @return the raw current reading
*/
/**************************************************************************/
int16_t Adafruit_INA219::getCurrent_raw() {
  uint16_t value;

  // Sometimes a sharp load will reset the INA219, which will
  // reset the cal register, meaning CURRENT and POWER will
  // not be available ... avoid this by always setting a cal
  // value even if it's an unfortunate extra step
  wireWriteRegister(INA219_REG_CALIBRATION, ina219_calValue);

  // Now we can safely read the CURRENT register!
  wireReadRegister(INA219_REG_CURRENT, &value);

  return (int16_t)value;
}

/**************************************************************************/
/*!
    @brief  Gets the raw power value (16-bit signed integer, so +-32767)
    @return raw power reading
*/
/**************************************************************************/
int16_t Adafruit_INA219::getPower_raw() {
  uint16_t value;

  // Sometimes a sharp load will reset the INA219, which will
  // reset the cal register, meaning CURRENT and POWER will
  // not be available ... avoid this by always setting a cal
  // value even if it's an unfortunate extra step
  wireWriteRegister(INA219_REG_CALIBRATION, ina219_calValue);

  // Now we can safely read the POWER register!
  wireReadRegister(INA219_REG_POWER, &value);

  return (int16_t)value;
}

/**************************************************************************/
/*!
    @brief  Gets the shunt voltage in mV (so +-327mV)
    @return the shunt voltage converted to millivolts
*/
/**************************************************************************/
float Adafruit_INA219::getShuntVoltage_mV() {
  int16_t value;
  value = getShuntVoltage_raw();
  return value * 0.01;
}

/**************************************************************************/
/*!
    @brief  Gets the shunt voltage in volts
    @return the bus voltage converted to volts
*/
/**************************************************************************/
float Adafruit_INA219::getBusVoltage_V() {
  int16_t value = getBusVoltage_raw();
  return value * 0.001;
}

/**************************************************************************/
/*!
    @brief  Gets the current value in mA, taking into account the
            config settings and current LSB
    @return the current reading convereted to milliamps
*/
/**************************************************************************/
float Adafruit_INA219::getCurrent_mA() {
  float valueDec = getCurrent_raw();
  valueDec /= ina219_currentDivider_mA;
  return valueDec;
}

/**************************************************************************/
/*!
    @brief  Gets the power value in mW, taking into account the
            config settings and current LSB
    @return power reading converted to milliwatts
*/
/**************************************************************************/
float Adafruit_INA219::getPower_mW() {
  float valueDec = getPower_raw();
  valueDec *= ina219_powerMultiplier_mW;
  return valueDec;
}