Overview

ina219 provides support for a popular power sensor from Texas Instruments:

Features

• Senses Bus Voltages from 0 to 26 V
• Reports Current, Voltage, and Power
• 16 Programmable Addresses
• High Accuracy: 0.5% (Maximum)
• Filtering Options
• Calibration Registers

Driver

The driver as the following functionality:

• Fast integer only calculation
• Support for I²C
• Calibration and Sense Resistor Options
• All measurement units are supported by physic

Tool

Use cmd/ina219 to retrieve measurement from the device.

Learn more

• INA219 at Adafruit

Example

Purpose: gather current, bus voltage and power.

This example uses either a INA219 connected via I²C.

package main

import (
    "fmt"
    "log"

    "periph.io/x/conn/v3/i2c/i2creg"
    "periph.io/x/devices/v3/ina219"
    "periph.io/x/host/v3"
)

func main() {
    // Make sure periph is initialized.
    if _, err := host.Init(); err != nil {
        log.Fatal(err)
    }

    // Open default I²C bus.
    bus, err := i2creg.Open("")
    if err != nil {
      log.Fatalf("failed to open I²C: %v", err)
    }
    defer bus.Close()

    // Create a new power sensor.
    sensor, err := ina219.New(bus, &ina219.DefaultOpts)
    if err != nil {
      log.Fatalln(err)
    }

    // Read values from sensor.
    measurement, err := sensor.Sense()
    if err != nil {
      log.Fatalln(err)
    }

    fmt.Println(measurement)
}

Calibration

The default options are for a 100mΩ sense resistor. To calibrate measure the actual value of the sense resistor and use that value in the ina219 options like so:

sensorOpts := ina219.Opts{
    Address       :0x40,
    SenseResistor :50 * physics.MilliOhm,
    MaxCurrent    :3200 * physics.MilliAmpere,
}
    //...
    sensor, err := ina219.New(bus, &sensorOpts)
    if err != nil {
        log.Fatal(err)
    }
    //...

Maximum Current

The maximum current for the ina219 is determined by the value of the sense resistor. There can’t be more than 320mV drop across the sense resistor. With a 100mΩ sense resistor the maximum current is 3.2Amps. Using V=IR, you can determine what the maximum current is for your sense resistor:

I = V/R

I = 0.320V / 0.1Ω

I = 3.2A

If the actual load current is bellow the maximum current for your sense resistor setting MaxCurrent to some amount above the maximum load current will give more resolution to the current and power readings. Example: Load of 500mA with 100mΩ.

sensorOpts := ina219.Opts{
    Address       :0x40,
    SenseResistor :100 * physics.MilliOhm,
    MaxCurrent    :1000 * physics.MilliAmpere,
}
    //...
    sensor, err := ina219.New(bus, &sensorOpts)
    if err != nil {
        log.Fatal(err)
    }
    //...

Buying

These links are for the INA219:

• Adafruit: adafruit.com
• Aliexpress:aliexpress.com (quality will vary among resellers)

ina219 products from Adafruit use the high accuracy B version of ina219, and good quality sense resistors. Other vendors my vary in quality of sense resistors and version of the ina219.

The periph authors do not endorse any specific seller. These are only provided for your convenience.

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