TI INA219 high-side current / power monitor codec (DETWS_ENABLE_INA219). More...

#include <stdint.h>

Macros
#define	INA219_REG_CONFIG 0x00
	configuration

#define	INA219_REG_SHUNT 0x01
	shunt voltage

#define	INA219_REG_BUS 0x02
	bus voltage

#define	INA219_REG_POWER 0x03
	power

#define	INA219_REG_CURRENT 0x04
	current

#define	INA219_REG_CALIBRATION 0x05
	calibration

Functions
int32_t	ina219_bus_mv (uint16_t raw)
	Decode the bus-voltage register to millivolts (value is bits [15:3], LSB 4 mV).

int32_t	ina219_shunt_uv (int16_t raw)
	Decode the shunt-voltage register to microvolts (signed, LSB 10 uV).

uint16_t	ina219_calibration (uint32_t current_lsb_ua, uint32_t shunt_mohm)
	Compute the calibration register from the current LSB (microamps per bit) and the shunt resistance (milliohms): `trunc(0.04096 / (current_LSB[A] * R[ohm]))` = `40960000 / (lsb_ua * shunt_mohm)`, clamped to 16 bits. (100 uA + 100 mohm -> 4096.) 0 on a zero denominator.

int32_t	ina219_current_ua (int16_t raw, uint32_t current_lsb_ua)
	Scale the raw current register to microamps (raw * current_lsb_ua).

int32_t	ina219_power_uw (int16_t raw, uint32_t current_lsb_ua)
	Scale the raw power register to microwatts (power LSB is 20 * current LSB).

bool	ina219_begin (uint8_t addr, uint32_t current_lsb_ua, uint32_t shunt_mohm)
	Program the INA219 at `addr:` write the calibration for `current_lsb_ua` (uA/bit) and `shunt_mohm` (milliohms), then the default 32 V / 320 mV continuous config.

bool	ina219_read_bus_mv (int32_t *millivolts)
	Read the bus voltage into `millivolts`.

bool	ina219_read_shunt_uv (int32_t *microvolts)
	Read the shunt voltage into `microvolts`.

bool	ina219_read_current_ua (int32_t *microamps)
	Read the current into `microamps` (needs the calibration set by ina219_begin).

bool	ina219_read_power_uw (int32_t *microwatts)
	Read the power into `microwatts` (needs the calibration set by ina219_begin).

Detailed Description

TI INA219 high-side current / power monitor codec (DETWS_ENABLE_INA219).

The INA219 measures the voltage across a shunt resistor (LSB 10 uV) and the bus voltage (LSB 4 mV, in the upper 13 bits of its register), and - once a calibration value derived from the shunt resistance and a chosen current LSB is programmed - reports current and power directly. From those you get how much current and power a circuit draws.

This codec is pure and host-tested: ina219_bus_mv / ina219_shunt_uv decode the voltage registers, ina219_calibration computes the calibration register, and ina219_current_ua / ina219_power_uw scale the raw current / power registers by the current LSB. On an ESP32 the binding programs the calibration + config and reads the registers over I2C (Wire); only that touches hardware.

A cheap solder-and-bench-test breakout: put it in series with a load and watch the current.

Author: Douglas Quigg (dstroy0)

Date: 2026

Definition in file ina219.h.

Macro Definition Documentation

◆ INA219_REG_CONFIG

#define INA219_REG_CONFIG 0x00

configuration

Definition at line 30 of file ina219.h.

◆ INA219_REG_SHUNT

#define INA219_REG_SHUNT 0x01

shunt voltage

Definition at line 31 of file ina219.h.

◆ INA219_REG_BUS

#define INA219_REG_BUS 0x02

bus voltage

Definition at line 32 of file ina219.h.

◆ INA219_REG_POWER

#define INA219_REG_POWER 0x03

power

Definition at line 33 of file ina219.h.

◆ INA219_REG_CURRENT

#define INA219_REG_CURRENT 0x04

current

Definition at line 34 of file ina219.h.

◆ INA219_REG_CALIBRATION

#define INA219_REG_CALIBRATION 0x05

calibration

Definition at line 35 of file ina219.h.

Function Documentation

◆ ina219_bus_mv()

int32_t ina219_bus_mv ( uint16_t raw )

Decode the bus-voltage register to millivolts (value is bits [15:3], LSB 4 mV).

◆ ina219_shunt_uv()

int32_t ina219_shunt_uv ( int16_t raw )

Decode the shunt-voltage register to microvolts (signed, LSB 10 uV).

◆ ina219_calibration()

uint16_t ina219_calibration	(	uint32_t	current_lsb_ua,
		uint32_t	shunt_mohm
	)

Compute the calibration register from the current LSB (microamps per bit) and the shunt resistance (milliohms): trunc(0.04096 / (current_LSB[A] * R[ohm])) = 40960000 / (lsb_ua * shunt_mohm), clamped to 16 bits. (100 uA + 100 mohm -> 4096.) 0 on a zero denominator.

◆ ina219_current_ua()

int32_t ina219_current_ua	(	int16_t	raw,
		uint32_t	current_lsb_ua
	)

Scale the raw current register to microamps (raw * current_lsb_ua).

◆ ina219_power_uw()

int32_t ina219_power_uw	(	int16_t	raw,
		uint32_t	current_lsb_ua
	)

Scale the raw power register to microwatts (power LSB is 20 * current LSB).

◆ ina219_begin()

bool ina219_begin	(	uint8_t	addr,
		uint32_t	current_lsb_ua,
		uint32_t	shunt_mohm
	)

Program the INA219 at addr: write the calibration for current_lsb_ua (uA/bit) and shunt_mohm (milliohms), then the default 32 V / 320 mV continuous config.

Returns: true on ack.

◆ ina219_read_bus_mv()

bool ina219_read_bus_mv ( int32_t * millivolts )

Read the bus voltage into millivolts.

Returns: false on I2C error.

◆ ina219_read_shunt_uv()

bool ina219_read_shunt_uv ( int32_t * microvolts )

Read the shunt voltage into microvolts.

Returns: false on I2C error.

◆ ina219_read_current_ua()

bool ina219_read_current_ua ( int32_t * microamps )

Read the current into microamps (needs the calibration set by ina219_begin).

◆ ina219_read_power_uw()

bool ina219_read_power_uw ( int32_t * microwatts )

Read the power into microwatts (needs the calibration set by ina219_begin).

Macros

Functions