CircuitPython Code

It's easy to use the INA219 sensor with CircuitPython and the Adafruit CircuitPython INA219 module.  This module allows you to easily write Python code that reads the current and more from the sensor.

First wire up a INA219 to your board exactly as shown on the previous pages for Arduino using an I2C interface.  Here's an example of wiring a Feather M0 to the sensor with I2C:

  • Board 3V to sensor Vcc
  • Board GND to sensor GND
  • Board SCL to sensor SCL
  • Board SDA to sensor SDA

In addition connect some load to measure the current from in series to the sensor's Vin- and Vin+ pins as mentioned on the wiring page.

Next you'll need to install the Adafruit CircuitPython INA219 library on your CircuitPython board.  Remember this module is for Adafruit CircuitPython firmware and not MicroPython.org firmware!

First make sure you are running the latest version of Adafruit CircuitPython for your board.

Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle.  For example the Circuit Playground Express guide has a great page on how to install the library bundle for both express and non-express boards.

Remember for non-express boards like the Trinket M0, Gemma M0, and Feather/Metro M0 basic you'll need to manually install the necessary libraries from the bundle:

  • adafruit_ina219.mpy
  • adafruit_bus_device

You can also download the adafruit_ina219.mpy from its releases page on Github.

Before continuing make sure your board's lib folder or root filesystem has the adafruit_ina219.mpy, and adafruit_bus_device files and folders copied over.

Next connect to the board's serial REPL so you are at the CircuitPython >>> prompt.

Usage

To demonstrate the usage of the sensor we'll initialize it and read the current and more from the board's Python REPL.  Run the following code to import the necessary modules and initialize the I2C connection with the sensor:

    import board
import busio
import adafruit_ina219
i2c = busio.I2C(board.SCL, board.SDA)
sensor = adafruit_ina219.INA219(i2c)
  

Remember if you're using a board that doesn't support hardware I2C (like the ESP8266) you need to use the bitbangio module instead:

import board
import bitbangio
import adafruit_ina219
i2c = bitbangio.I2C(board.SCL, board.SDA)
sensor = adafruit_ina219.INA219(i2c)

Now you're ready to read values from the sensor using any of these functions:

  • get_shunt_voltage_mV() - The shunt voltage in millivolts.
  • get_bus_voltage_V() - The bus voltage in volts.
  • get_current_mA() - The current in milliamps.
print('Shunt voltage: {} mV'.format(sensor.get_shunt_voltage_mV()))
print('Bus voltage: {} V'.format(sensor.get_bus_voltage_V()))
print('Current: {} mA'.format(sensor.get_current_mA()))

That's all there is to using the INA219 with CircuitPython!

Here's a full example to print the voltage and current every second.  Save this as main.py on your board's filesystem and check the output from the serial REPL.  Also remember if you're using the ESP8266 you need to change the initialization to use the bitbangio module!

import board
import busio
import time

import adafruit_ina219

# Initialize I2C bus and sensor.
i2c = busio.I2C(board.SCL, board.SDA)
sensor = adafruit_ina219.INA219(i2c)

# Main loop prints voltage and current every second.
while True:
    print('Shunt voltage: {} mV'.format(sensor.get_shunt_voltage_mV()))
    print('Bus voltage: {} V'.format(sensor.get_bus_voltage_V()))
    print('Current: {} mA'.format(sensor.get_current_mA()))
    time.sleep(1.0)
Last updated on 2018-01-17 at 12.11.40 PM Published on 2012-10-26 at 10.55.48 AM