GY-63_MS5611/libraries/INA219

INA219

Arduino library for INA219 voltage, current and power sensor.

Description

Experimental library for the INA219 power sensor. Minimal tested, so usage remarks and comments are welcome.

Read datasheet for details.

USE WITH CARE

The INA219 is a voltage, current and power measurement device. Maxima, see datasheet, chapter 7, esp 7.5

description	max	unit	notes
bus voltage	32	Volt	depends on BRNG setting
shunt voltage	320	mVolt	depends on PGA setting

0.2.0 Breaking change

Version 0.2.0 introduced a breaking change. You cannot set the pins in begin() any more. This reduces the dependency of processor dependent Wire implementations. The user has to call Wire.begin() and can optionally set the Wire pins before calling begin().

Special characters

• Ω == Ohm = ALT-234 (Windows)
• µ == micro = ALT-0181 (Windows)

Related

• https://www.ti.com/product/INA219#tech-docs
• https://www.ti.com/document-viewer/INA219/datasheet
• https://github.com/RobTillaart/INA219
• https://github.com/RobTillaart/INA226

I2C

Address

The sensor can be configured to use 1 of 16 I2C addresses between 0x40 and 0x4F. The address depends on how the A0 and A1 address lines are connected to the SCL, SDA, GND and VCC pins. (datasheet chapter 8.5.5.1 Serial Bus Address)

Performance

Datasheet states it supports 1 KHz .. 2.56 MHz. Note: higher speeds need smaller pull up resistors.

Some timings in micros for INA.getMode() on an Arduino UNO. This is just one readRegister call, similar to most functions.

Above 600 KHz there is little performance gain.

speed	time	speed	time	speed	time	speed	time
100000	560	150000	396	200000	320	250000	272
300000	232	350000	208	400000	196	450000	176
500000	172	550000	164	600000	152	650000	152
700000	144	750000	144	800000	140

use INA219_test_I2C.ino

Interface

#include "INA219.h"

Constructor

• INA219(const uint8_t address, TwoWire *wire = Wire) Constructor to set address and optional Wire interface.
• bool begin() UNO ea. initializes the class. Returns true if the INA219 address (set in the constructor) is on the I2C bus.
• bool isConnected() Returns true if the INA219 address (set in the constructor) is on the I2C bus.

Core Functions

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

• float getShuntVoltage() idem.
• float getBusVoltage() idem. Max 32 Volt.
• float getPower() returns the current times BusVoltage in Watt.
• float getCurrent() returns the current through the shunt in Ampere.

The library has helper functions to convert above output to a more appropriate scale of units.

Helper functions for the milli scale.

• float getBusVoltage_mV() idem, returns millivolts. Note: returns -100 if the math overflow bit is set.
• float getShuntVoltage_mV() idem, returns millivolts.
• float getCurrent_mA() idem in milliAmpere.
• float getPower_mW() idem in milliWatt.

Helper functions for the micro scale.

• float getBusVoltage_uV() idem microVolt.
• float getShuntVoltage_uV() idem microVolt.
• float getCurrent_uA() idem in microAmpere.
• float getPower_uW() idem, in microWatt.

Indicator flags

• bool getMathOverflowFlag() internal math overflow.
• bool getConversionFlag() conversion is ready. Especially useful in non-continuous modi.

Configuration

Note: the conversion runs in the background and if done the value is stored in a register. The core functions can always be read from the registers, so they will not block. Result can be that you get the very same value if no new value is ready.

• void reset() software power on reset. This implies that calibration with setMaxCurrentShunt() needs to be redone. See section below.
• bool setBusVoltageRange(uint8_t voltage = 16) set to 16 or 32. Values < 16 map to 16 and values between 16 and 32 map to 32. Values above 32 return false.
• uint8_t getBusVoltageRange() returns 16 or 32. (Volts)
• bool setGain(uint8_t factor = 1) factor = 1, 2, 4, 8. Determines the shunt voltage range. 40, 80, 160 or 320 mV. Returns false if factor is not a valid value.
• uint8_t getGain() returns set factor.
• bool setBusADC(uint8_t mask = 0x03) check datasheet for meaning of mask. Returns false if mask > 0x0F.
• uint8_t getBusADC() returns mask.
• bool setShuntADC(uint8_t mask = 0x03) check datasheet for meaning of mask. Returns false if mask > 0x0F.
• uint8_t getShuntADC() returns mask.

mask = both resolution + averaging multiple samples. minus - == don't care

bit mask	value	description	conversion time
0-00	0 / 4	9 bit resolution	84 μs
0-01	1 / 5	10 bit resolution	148 μs
0-10	2 / 6	11 bit resolution	276 μs
0-11	3 / 7	12 bit resolution	532 μs
1000	8	12 bit 1 sample	532 μs
1001	9	2 samples	1.06 ms
1010	10	4 samples	2.13 ms
1011	11	8 samples	4.26 ms
1100	12	16 samples	8.51 ms
1101	13	32 samples	17.02 ms
1110	14	64 samples	34.05 ms
1111	15	128 samples	68.10 ms

• note that a new value can take a while depending on value set.
• note that you cannot set e.g. 9 bits and 16 samples.

Operating mode

See details datasheet,

• bool setMode(uint8_t mode = 7) mode = 0..7. The value 7 == ShuntBusContinuous mode.
• uint8_t getMode() returns the mode (0..7) set.

Descriptive mode functions (convenience wrappers).

• bool shutDown() mode 0
• bool setModeShuntTrigger() mode 1 - how to trigger to be investigated.
• bool setModeBusTrigger() mode 2
• bool setModeShuntBusTrigger() mode 3
• bool setModeADCOff() mode 4
• bool setModeShuntContinuous() mode 5
• bool setModeBusContinuous() mode 6
• bool setModeShuntBusContinuous() mode 7 - default

Calibration

See details datasheet.

Calibration is mandatory for getCurrent() and getPower() to work.

• bool setMaxCurrentShunt(float ampere = 20.0, float ohm = 0.002) set the calibration register based upon the shunt and the max ampere. From this the LSB is derived. Note the function will round up the LSB to nearest round value by default. This may cause loss of precision. The function may force normalization if underflow detected. The user must check the return value == true, otherwise the calibration register is not set.
• bool isCalibrated() returns true if CurrentLSB has been calculated by setMaxCurrentShunt().
• float getCurrentLSB() returns the LSB in Ampere == precision of the calibration.
• float getCurrentLSB_mA() returns the LSB in milliampere.
• float getCurrentLSB_uA() returns the LSB in microampere.
• float getShunt() returns the value set for the shunt.
• float getMaxCurrent() returns the value for the maxCurrent which can be corrected.

To print these values one might use https://github.com/RobTillaart/printHelpers to get the values in scientific notation like "3.5e-6"

debugging

• uint16_t getRegister(uint8_t reg) fetch registers directly, meant for debugging only. Check datasheet.

Future

Must

• find time to test more
  • test different loads
  • all functions.
• update documentation

Should

• create unit tests
• test performance
  • verify conversion time
• write and verify examples
• add a setCurrentLSB(uint16_t mA) function ?
  • maxAmpere as derived value

Could

• calibration
  • autocorrect _current_LSB round number
  • maxCurrent? how much?
  • can the calibration math be optimized
    • integer only?
    • less iterations?
    • local var for current_lsb?
    • does this matter as it is often a one time action?
• disconnected load,
  • can it be recognized? => current drop?
• cache configuration ? ==> 2 bytes
  • what is gained? both getting and setting is faster. a few milliseconds per call?
  • about a dozen times used,
  • flag for forced read in functions setMode(uint8_t mode, bool forced = false)
• create defines for several masks / magic numbers

Wont

• initial current 20A and shunt 0.002 Ω in begin()
  • can't be sure so user is responsible

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