INA3221 I2C

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mongoose-os-libs/ina3221-i2c	mgos_ina3221.h

A Mongoose library for Texas Instruments' 3-channel current sensor.

Implementation details

The INA3221 is a simple I2C device that measures current through shunt resistors on three separate channels. It is able to measure the voltage on each channel (max 26V, in 8mV increments) and the voltage drop over the shunt resistor in 40uV increments with a range of 163.8mV, and is quite precise.

Using a 0.1Ohm shunt resistor, the maximum current that can be measured is 1.638A. Each channel can be enabled/disabled and polled individually.

API Description

Create an INA3221 object using mgos_ina3221_create(), set the shunt resistor values for each channel using mgos_ina3221_set_shunt_resistance(), then call mgos_ina3221_get_bus_voltage() to get the bus voltage, call mgos_ina3221_get_shunt_voltage() to get the voltage drop over the shunt resistor, and mgos_ina3221_get_current() to get the current flowing through the channel.

Valid channels are 1, 2 or 3 (ie. they are 1-based).

Example application

#include "mgos.h"
#include "mgos_config.h"
#include "mgos_ina3221.h"

static void ina3221_timer_cb(void *user_data) {
  struct mgos_ina3221 *sensor = (struct mgos_ina3221 *)user_data;

  if (!sensor) return;

  for (uint8_t i=1; i<4; i++) {
    float bus, shunt, current, res;
    mgos_ina3221_get_bus_voltage(sensor, i, &bus);
    mgos_ina3221_get_shunt_resistance(sensor, i, &res);
    mgos_ina3221_get_shunt_voltage(sensor, i, &shunt);
    mgos_ina3221_get_current(sensor, i, &current);
    LOG(LL_INFO, ("Chan[%u]: Vbus=%.3f V Vshunt=%.0f uV Rshunt=%.3f Ohm Ishunt=%.1f mA",
      i, bus, shunt*1e6, res, current*1e3));
  }
}

enum mgos_app_init_result mgos_app_init(void) {
  struct mgos_ina3221 *sensor;

  sensor = mgos_ina3221_create(mgos_i2c_get_global(), mgos_sys_config_get_ina3221_i2caddr());
  if (!sensor) {
    LOG(LL_ERROR, ("Could not create INA3221 sensor"));
    return false;
  }

  mgos_set_timer(1000, true, ina3221_timer_cb, sensor);

  return MGOS_APP_INIT_SUCCESS;
}

Disclaimer

This project is not an official Google project. It is not supported by Google and Google specifically disclaims all warranties as to its quality, merchantability, or fitness for a particular purpose.

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mgos_ina3221_create

struct mgos_ina3221 *mgos_ina3221_create(struct mgos_i2c *i2c, uint8_t i2caddr);

Initialize a INA3221 on the I2C bus i2c at address specified in i2caddr parameter (default INA3221 is on address 0x40). The sensor will be polled for validity, upon success a new struct mgos_ina3221 is allocated and returned. If the device could not be found, NULL is returned.

mgos_ina3221_destroy

void mgos_ina3221_destroy(struct mgos_ina3221 **sensor);

Destroy the data structure associated with a INA3221 device. The reference to the pointer of the struct mgos_ina3221 has to be provided, and upon successful destruction, its associated memory will be freed and the pointer set to NULL.

mgos_ina3221_get_bus_voltage

bool mgos_ina3221_get_bus_voltage(struct mgos_ina3221 *sensor, uint8_t chan, float *volts);

Measure the bus voltage on channel chan (which can be 1, 2, or 3). Return the measured voltage in *volts, in units of Volts. Returns true on success and false on failure, in which case *volts is unspecified.

mgos_ina3221_get_shunt_voltage

bool mgos_ina3221_get_shunt_voltage(struct mgos_ina3221 *sensor, uint8_t chan, float *volts);

Measure the shunt voltage on channel chan (which can be 1, 2, or 3). Return the measured voltage in *volts, in units of Volts. Returns true on success and false on failure, in which case *volts is unspecified.

mgos_ina3221_set_shunt_resistance

bool mgos_ina3221_set_shunt_resistance(struct mgos_ina3221 *sensor, uint8_t chan, float ohms);

Set the shunt resistor value in units of Ohms on channel chan (which can be 1, 2 or 3). Typical values is ohms=0.100 (which yields a 1.6A range on the current sensor). Returns true on success and false on failure.

mgos_ina3221_get_shunt_resistance

bool mgos_ina3221_get_shunt_resistance(struct mgos_ina3221 *sensor, uint8_t chan, float *ohms);

Get the shunt resistor value in units of Ohms on channel chan (which can be 1, 2 or 3). Returns true on success and false on failure, in which case *ohms is unspecified.

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