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/**************************************************************************/
/*!
@file Adafruit_INA219.cpp
@author K.Townsend (Adafruit Industries)
@license BSD (see license.txt)
Driver for the INA219 current sensor
This is a library for the Adafruit INA219 breakou
Adafruit invests time and resources providing this open source code,
please support Adafruit and open-source hardware by purchasing
products from Adafruit!
@section HISTORY
v1.0 - First release
*/
/**************************************************************************/
#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)
{
Wire.beginTransmission(ina219_i2caddr);
#if ARDUINO >= 100
Wire.write(reg); // Register
Wire.write((value >> 8) & 0xFF); // Upper 8-bits
Wire.write(value & 0xFF); // Lower 8-bits
#else
Wire.send(reg); // Register
Wire.send(value >> 8); // Upper 8-bits
Wire.send(value & 0xFF); // Lower 8-bits
#endif
Wire.endTransmission();
}
/**************************************************************************/
/*!
@brief Reads a 16 bit values over I2C
*/
/**************************************************************************/
void Adafruit_INA219::wireReadRegister(uint8_t reg, uint16_t *value)
{
Wire.beginTransmission(ina219_i2caddr);
#if ARDUINO >= 100
Wire.write(reg); // Register
#else
Wire.send(reg); // Register
#endif
Wire.endTransmission();
delay(1); // Max 12-bit conversion time is 586us per sample
Wire.requestFrom(ina219_i2caddr, (uint8_t)2);
#if ARDUINO >= 100
// Shift values to create properly formed integer
*value = ((Wire.read() << 8) | Wire.read());
#else
// Shift values to create properly formed integer
*value = ((Wire.receive() << 8) | Wire.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_powerDivider_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 |
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