INA219

A library for interacting with the Texas Instruments INA219 high side current and power monitoring chip via I2C using Elixir ALE.

I'm using the Adafruit INA219 breakout for prototyping, so am using their calibrations straight from their Arduino library, but you can do the maths and calibrate it yourself if you're using a different shunt resistor value.

Usage

In your config.exs add the following:

config :ina219,
  devices: [
    %{
      bus: "i2c-1",
      address: 0x41,
      commands: [:calibrate_32V_2A!],
      current_divisor: 10,
      power_divisor: 2
    }
  ]

You must set the bus and address values according to your system.

Calibration

Calibrating these wee chips is a bit of a pain in the donkey, but is easily achieved by following the equation in the data sheet. Once you have the calibration and divisor values you wish to use you can configure the device manually (see the hexdocs for INA219.Commands for more information). For example:

%{
  bus: "i2c-1",
  address: 0x41,
  commands: [
    calibrate: 8192,
    bus_voltage_range: 32,
    shunt_voltage_pga: 8,
    bus_adc_resolution_and_averaging: {1, 12},
    shunt_adc_resolution_and_averaging: {1, 12},
    mode: :shunt_and_bus_voltage_continuous
  ],
  current_divisor: 10,
  power_divisor: 2
}

Installation

If available in Hex, the package can be installed by adding ina219 to your list of dependencies in mix.exs:

def deps do
  [
    {:ina219, "~> 0.1.0"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/ina219.