ina219 v0.1.0

INA219 high-side current and power monitor.

Application scenarios

• Battery or supply current logging.
• A motor or LED load monitor.
• A USB power budget check.

Contract

uint8_t ina219_init(ina219_t *device, ina219_port_t port, uint8_t i2c_address,
                    uint16_t shunt_milliohm, uint16_t current_lsb_ua);
uint8_t ina219_read_bus_voltage_mv(ina219_t *device, uint32_t *millivolts);
uint8_t ina219_read_shunt_voltage_uv(ina219_t *device, int32_t *microvolts);
uint8_t ina219_read_current_ua(ina219_t *device, int32_t *microamps);
uint8_t ina219_read_power_mw(ina219_t *device, uint32_t *milliwatts);

• init writes the 32 V / +-320 mV / 12-bit continuous configuration and

the calibration register.

• Bus voltage LSB is 4 mV; shunt voltage LSB is 10 uV.
• Current LSB is the value passed to init; power LSB is 20 times that.
• Returns 1 on success, 0 on a bad argument or a bus error.

Parameters

• I2C address 0x40..0x4F.
• Shunt resistor in milliohms; current LSB in microamps.
• Keep the shunt voltage within the selected PGA range.

Memory and timing

• 8 bytes; one 2-byte register write at init and one 2-byte read per value.
• Continuous conversion; a read returns the latest sample.

Integration

ina219_t monitor;
ina219_init(&monitor, board_i2c_port(), 0x40, 100, 100);
uint32_t millivolts;
ina219_read_bus_voltage_mv(&monitor, &millivolts);

Adapters

• The adapter issues a register write followed by a repeated-start read.
• Reference: LibDriver ina219 (MIT) and the Texas Instruments INA219 datasheet.
• This implementation is original.

When not to use

• A high-side voltage beyond 32 V; use an isolated or higher-voltage monitor.
• A precision energy meter; add a dedicated metering IC.

Verification

make test covers the config and calibration writes, bus/shunt/current/power

conversion, and range rejection.

void *context;
uint8_t (*write)(void *context, uint8_t address, uint8_t reg,
const uint8_t *data, uint16_t length);
uint8_t (*read)(void *context, uint8_t address, uint8_t reg,
uint8_t *data, uint16_t length);

ina219_port_t port;
uint8_t i2c_address;
uint16_t current_lsb_ua;