Tero's Arduino Blog

Using Arduino with Ada

Measuring current with INA219 sensor

To optimize the power usage of my Arduino devices, I first needed to measure the power usage.

I could have done it traditionally with multimeter, but then I found Adafruit's INA219 sensor breakout board.

Adafruit also has nice tutorial for the sensor (which I actually bought from oomlout.co.uk to avoid customs/extra taxes as European).

So, for the setup I gathered following parts:

  • Arduino UNO, for reading the INA219 sensor
  • The INA219 sensor itself
  • Olimexino-328 as a target device for measurements
  • Sparkfun Breadboard Power Supply for providing power to Olimexino-328.
  • A small breadboard and a few jumper wires

When assembled together, the setup looks like this:


The code consists of my I2C package and translation of Adafruit's INA219 code (written in C) to Ada.

The INA219 Ada package interface looks like this:

package INA219 is
   procedure Init;

   function Get_Bus_Voltage return Interfaces.Unsigned_16;
   function Get_Shunt_Voltage return Interfaces.Unsigned_16;
   function Get_Current return Interfaces.Unsigned_16;
   function Get_Power return Interfaces.Unsigned_16;

   function Get_Error return Boolean;

   procedure Set_Calibration_32V_2A;
end INA219;

Procedure Init needs to be called before other functions. It initializes the I2C bus and sets the default calibration.

Once the device is initialized and calibrated, you can query voltage, current, and power values with the related functions.

   AVR.UART.Put ("   ***"); AVR.UART.CRLF;
   AVR.UART.Put (INA219.Get_Bus_Voltage); AVR.UART.CRLF;
   AVR.UART.Put (INA219.Get_Shunt_Voltage); AVR.UART.CRLF;
   AVR.UART.Put (INA219.Get_Current); AVR.UART.CRLF;
   AVR.UART.Put (INA219.Get_Power); AVR.UART.CRLF;
   delay 1.0;
end loop;

Using the above program and opening the serial console, we can see how much power our target device draws. If you want to know how to change this value, you need to either do it by yourself or wait for future articles about AVR power saving using AVR-Ada :).

The code for the program is available in my arduino-blog repository (see examples/ina219 directory).

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