INA228

January 10, 2026 · View on GitHub

INA228

Arduino library for the INA228 power sensor.

Description

Experimental

This library controls the INA228, a device that measures voltage, current, power, temperature and more.

The INA228 sensor differs from the better known INA226. Most important difference is that the INA228 has a 20 bit ADC. This should result in higher precision however this is expected to only be visible with stable loads and low noise.

An important difference is that the INA228 works up to 85 Volts, which is more than twice the 36 volt of the INA226. The INA228 has a build in temperature sensor (±1°C) to be used for monitoring and temperature compensation.

Finally the INA228 has an energy and charge register. These are values accumulated over time, and only work in continuous mode. (to be investigated what those mean ).

The INA228 also provides an ALERT line, to generate an interrupt in case a predefined threshold has been met. This can be an under- or over-voltage, temperature or power limit. The library does not handle these interrupts. The alert / limits part of the library's API still needs a redesign.

The library is limited tested and verified with hardware.

==> USE WITH CARE

Feedback as always is welcome.

Breaking change 0.3.0

The function getCharge() is updated as the value can be negative too. The previous versions assumed it could only be positive. See #22. 0.3.0 fixed the getEnergy() which only can have positive values and was broken in 0.2.0. Versions before 0.3.0 are obsolete now.

Details

The INA228 is a voltage, current and power measurement device. A few important data, Read the datasheet for the details, Section 7, Page 12++.

description	value	notes
bus voltage	85 Volt	unclear for how long.
ADC	20 bit
alert timing	75 µs.

Two breakout boards are known, with completely different maximum current. This max current depends on the width of the traces on the PCB and the shunt used. See the links below for more details.

supplier	Shunt Ω	Current	Shunt V	URL
Adafruit	0.015	10 Amp	150 mV	https://www.adafruit.com/product/5832
Mateksys	0.0002	204 Amp	41 mV	https://www.mateksys.com/?portfolio=i2c-ina-bm

Both are verified to work but not the full range. (See #10)

Calibrating

Note the power and the current are not meaningful without calibrating the sensor. Also the values are not meaningful if there is no shunt connected.

Schema LOW SIDE

         GND                           VCC
          |                             |
          |                             |
          |            +----[ LOAD ]----+
          |            |                |
          |            |                |
      /-------------------------------------\
      |  VIN-         VIN+             VBUS |
      |                                     |
      |                                     |
      |         INA 228 BREAKOUT            |
      |                                     |
      |                                     |
      \-------------------------------------/

Tested

Schema HIGH SIDE

         GND                          VCC
          |                            |
          |                            |
          +---[ LOAD ]---+        +----+
                         |        |    |
                         |        |    |
      /-------------------------------------\
      |                 VIN-     VIN+  VBUS |
      |                                     |
      |                                     |
      |         INA 228 BREAKOUT            |
      |                                     |
      |                                     |
      \-------------------------------------/

Tested

Special characters

Ω == Ohm = ALT-234 (Windows)
µ == micro = ALT-0181 (Windows)
° == degree = ALT-0176 (Windows)
± == plus minus = ALT-0177 (Windows)

https://www.ti.com/product/INA228#tech-docs
https://www.ti.com/product/INA228#params
https://www.ti.com/document-viewer/INA228/datasheet
https://github.com/RobTillaart/INA219 26 Volt, I2C, 12 bit
https://github.com/RobTillaart/INA226 36 Volt, I2C, 16 bit
https://github.com/RobTillaart/INA228 85 Volt, I2C, 20 bit
https://github.com/RobTillaart/INA236 48 Volt, I2C, 16 bit
https://github.com/RobTillaart/INA229 85 Volt, SPI, 20 bit
https://github.com/RobTillaart/INA239 85 Volt, SPI, 16 bit
https://github.com/RobTillaart/INA3221_RT 26 Volt, I2C, 13 bits (3 channel)
https://www.adafruit.com/product/5832
https://www.mateksys.com/?portfolio=i2c-ina-bm
https://github.com/RobTillaart/printHelpers (for scientific notation)

I2C

Address

The sensor can have 16 different I2C addresses, which depends on how the A0 and A1 address lines are connected to the SCL, SDA, GND and VCC pins.

See table - from datasheet table 7-2, page 19.

A1	A0	Addr	HEX	A1	A0	Addr	HEX
GND	GND	64	0x40	SDA	GND	72	0x48
GND	VCC	65	0x41	SDA	VCC	73	0x49
GND	SDA	66	0x42	SDA	SDA	74	0x4A
GND	SCL	67	0x43	SDA	SCL	75	0x4B
VCC	GND	68	0x44	SCL	GND	76	0x4C
VCC	VCC	69	0x45	SCL	VCC	77	0x4D
VCC	SDA	70	0x46	SCL	SDA	78	0x4E
VCC	SCL	71	0x47	SCL	SCL	79	0x4F

Note this might differ per breakout board.

Performance

Run INA228_performance.ino sketch to get a first indication. Numbers below are based upon tests with the Adafruit board.

Time in micros, I2C speed in kHz.

I2C	function	time	notes
100	getBusVoltage	684	100%
100	getShuntVoltage	1248
100	getCurrent	684
100	getPower	684
100	getTemperature	580
100	getEnergy	940
100	getCharge	960
			other functions similar gain.
200	getBusVoltage	404	60%
400	getBusVoltage	252	37%
800	getBusVoltage	184	27%

Most non core functions are as fast as getTemperature()

I2C multiplexing

Sometimes you need to control more devices than possible with the default address range the device provides. This is possible with an I2C multiplexer e.g. TCA9548 which creates up to eight channels (think of it as I2C subnets) which can use the complete address range of the device.

Drawback of using a multiplexer is that it takes more administration in your code e.g. which device is on which channel. This will slow down the access, which must be taken into account when deciding which devices are on which channel. Also note that switching between channels will slow down other devices too if they are behind the multiplexer.

https://github.com/RobTillaart/TCA9548

Interface

#include "INA228.h"

Constructor

INA228(const uint8_t address, TwoWire *wire = Wire) Constructor to set the address and optional Wire interface.
bool begin() initializes the class. Returns true if the INA228 address is on the I2C bus.
- Note: one needs to set Wire.begin() before calling begin().
- Note: call setMaxCurrentShunt(maxCurrent, shunt) to calibrate your INA228
bool isConnected() returns true if the INA228 address is on the I2C bus.
uint8_t getAddress() returns the address set in the constructor.

BUS VOLTAGE

Main function + wrappers.

float getBusVoltage() idem. Returns value in volts. Max 85 Volt. This value is always positive.
float getBusVolt()
float getBusMilliVolt()
float getBusMicroVolt()

SHUNT VOLTAGE

float getShuntVoltage() idem. Returns value in volts. Note the value can be positive or negative as the INA228 is bidirectional.
float getShuntVolt()
float getShuntMilliVolt()
float getShuntMicroVolt()
int32_t getShuntVoltageRAW()

SHUNT CURRENT

float getCurrent() returns the current through the shunt in Ampere. Note this value can be positive or negative as the INA228 is bidirectional.
float getAmpere()
float getMilliAmpere()
float getMicroAmpere()

POWER

float getPower() returns the current x BusVoltage in Watt.
float getWatt()
float getMilliWatt()
float getMicroWatt()
float getKiloWatt()

TEMPERATURE

float getTemperature() returns the temperature in Celsius.

ENERGY

See page 13++, page 32, 8.1.2

The getEnergy() only has meaning in continuous mode. This is an accumulation register and can be reset to zero by setAccumulation(1). Note this function resets other accumulation registers too.

The accuracy of getEnergy() is 1.0% full scale (maximum).

double getEnergy() return Joule (elaborate).
double getJoule()
double getMegaJoule()
double getKiloJoule()
double getMilliJoule()
double getMicroJoule()
double getWattHour()
double getKiloWattHour()

CHARGE

The getCharge() only has meaning in continuous mode. This is an accumulation register and can be reset to zero by setAccumulation(1). Note this function resets other accumulation registers too.

The accuracy of getCharge() is 1.0% full scale (maximum).

double getCharge() return Coulomb (elaborate).
double getCoulomb()
double getMilliCoulomb()
double getMicroCoulomb()

Configuration

Read datasheet for details, section 7.6.1.1, page 22

void reset() Resets the device, be aware that you need to calibrate the sensor (shunt register) again ==> call setMaxCurrentShunt() and more.
bool setAccumulation(uint8_t value) value: 0 == normal operation,
1 = clear Energy and Charge accumulation registers.
bool getAccumulation() return set value. (TODO check).
void setConversionDelay(uint8_t steps) Conversion delay in 0..255 steps of 2 ms
uint8_t getConversionDelay() return set value.
void setTemperatureCompensation(bool on) see Shunt temperature coefficient below.
bool getTemperatureCompensation() return set value.
bool setADCRange(bool flag) flag = false => ~163.84 mV, true => ~40.96 mV Since 0.3.1 setADCRange() calls setMaxCurrentShunt() to update the internal LSB values.
bool getADCRange() return set value.

TODO: wrapper + better name for setAccumulation(). resetEnergyCharge() { setAccumulation(true) }

TODO: examples to show the effect of the ADC configuration.

ADC mode

Read datasheet for details, section 7.6.1.2, page 22++

bool setMode(uint8_t mode = INA228_MODE_CONT_TEMP_BUS_SHUNT) default all on.
uint8_t getMode() return set value.

MODE	value	notes
INA228_MODE_SHUTDOWN	0x00	See 0x08.
INA228_MODE_TRIG_BUS	0x01
INA228_MODE_TRIG_SHUNT	0x02
INA228_MODE_TRIG_BUS_SHUNT	0x03
INA228_MODE_TRIG_TEMP	0x04
INA228_MODE_TRIG_TEMP_BUS	0x05
INA228_MODE_TRIG_TEMP_SHUNT	0x06
INA228_MODE_TRIG_TEMP_BUS_SHUNT	0x07
INA228_MODE_SHUTDOWN2	0x08	There are two shutdowns.
INA228_MODE_CONT_BUS	0x09
INA228_MODE_CONT_SHUNT	0x0A
INA228_MODE_CONT_BUS_SHUNT	0x0B
INA228_MODE_CONT_TEMP	0x0C
INA228_MODE_CONT_TEMP_BUS	0x0D
INA228_MODE_CONT_TEMP_SHUNT	0x0E
INA228_MODE_CONT_TEMP_BUS_SHUNT	0x0F

ADC conversion time

bool setBusVoltageConversionTime(uint8_t bvct = INA226_1052_us)
uint8_t getBusVoltageConversionTime() return set value.
bool setShuntVoltageConversionTime(uint8_t svct = INA226_1052_us)
uint8_t getShuntVoltageConversionTime() return set value.
bool setTemperatureConversionTime(uint8_t tct = INA226_1052_us)
uint8_t getTemperatureConversionTime() return set value.

TIMING	value	notes
INA228_50_us	0
INA228_84_us	1
INA228_150_us	2
INA228_280_us	3
INA228_540_us	4
INA228_1052_us	5
INA228_2074_us	6
INA228_4120_us	7

ADC Average

bool setAverage(uint8_t avg = INA228_1_SAMPLE)
uint8_t getAverage() return set value.

AVERAGE	value	notes
INA228_1_SAMPLE	0
INA228_4_SAMPLES	1
INA228_16_SAMPLES	2
INA228_64_SAMPLES	3
INA228_128_SAMPLES	4
INA228_256_SAMPLES	5
INA228_512_SAMPLES	6
INA228_1024_SAMPLES	7

Shunt Calibration

To elaborate, read datasheet for details.

Note: setMaxCurrentShunt() must be called to calibrate your sensor. Otherwise several functions will return zero or incorrect data.

int setMaxCurrentShunt(float maxCurrent, float shunt) The maxCurrent depends on breakout used, See section above. The shunt should be 0.0001 Ω and up.
- returns 0 if OK.
- returns -2 if shunt < 0.0001 Ohm. ( Mateksys == 0.0002 Ω )
- returns -3 if maxCurrent < 0.0.
bool isCalibrated() is valid calibration value. The currentLSB > 0.
float getMaxCurrent() return set value.
float getShunt() return set value.
float getCurrentLSB() return actual currenLSB. 0.0 means not calibrated.

Shunt temperature coefficient

Read datasheet for details, page 16.

The INA228 can compensate for shunt temperature variance to increase accuracy. The reference temperature is 25°C.

Enter the coefficient with setShuntTemperatureCoefficent(uint16_t ppm).
Enable the function with setTemperatureCompensation(true).

In formula:

Radjusted = Rnominal + (Rnominal x (temperature - 25) x PPM) * 10e-6;

bool setShuntTemperatureCoefficent(uint16_t ppm = 0) ppm = 0..16383 ppm/°C. Default 0 for easy reset. Returns false if ppm is out of range.
uint16_t getShuntTemperatureCoefficent() returns the set value (default 0).

Diagnose alert

Read datasheet for details, section 7.6.1.12, page 26++.

void setDiagnoseAlert(uint16_t flags) set all flags as bit mask.
uint16_t getDiagnoseAlert() return all flags as bit mask.

INA228.h has an enum for the bit fields.

void setDiagnoseAlertBit(uint8_t bit) set individual bit.
void clearDiagnoseAlertBit(uint8_t bit) clear individual bit.
uint16_t getDiagnoseAlertBit(uint8_t bit) return individual bit.

Threshold and Limits

Read datasheet for details, section 7.3.7, page 16++

Note: the implementation of this part is rather minimalistic and might be changed / extended in the future.

Shunt

void setShuntOvervoltageTH(uint16_t threshold)
uint16_t getShuntOvervoltageTH()
void setShuntUndervoltageTH(uint16_t threshold)
uint16_t getShuntUndervoltageTH()

Bus

void setBusOvervoltageTH(uint16_t threshold)
uint16_t getBusOvervoltageTH()
void setBusUndervoltageTH(uint16_t threshold)
uint16_t getBusUndervoltageTH()

Temperature

void setTemperatureOverLimitTH(uint16_t threshold)
uint16_t getTemperatureOverLimitTH()

Power

void setPowerOverLimitTH(uint16_t threshold)
uint16_t getPowerOverLimitTH()

Manufacturer and ID

bool getManufacturer() Returns 0x5449, can be used to check right sensor.
uint16_t getDieID() Returns 0x228, can be used to check right sensor.
uint16_t getRevision() Returns revision, probably 0x01.

Future

Must

update documentation.
test and verify.
DiagnoseAlertBit functions
- redo API (0.2.0)
keep in sync with INA226 where possible.
keep in sync with INA238 where possible.

Should

TODO's in code and docs.
add error handling.
keep in sync with INA226 where possible.
how to detect nothing connected?
- vshunt > maxVShunt (new variable)
- current > maxCurrent

Could

write examples, (please share yours).
improve unit tests
clean up magic numbers in the code

Won't

cache registers for performance
- first get library working / tested.
- reset should reread all cached values...

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