Simple_INA238

Easily Access the INA238’s Registers and Measured Values on Arduino

The INA238 is an ultra-precise digital power monitor with a 16-bit delta-sigma ADC, designed for high-accuracy current-sensing applications. With this Arduino library, you can quickly configure the INA238, read measurements (current, bus voltage, temperature, and power), and harness the device’s ultra-low offset, wide common-mode range, and built-in temperature sensor—all with minimal code.

Key Features

• High-Resolution 16-bit Delta-Sigma ADC
• Current Monitoring Accuracy
  • Offset Voltage: ±5 µV (max)
  • Offset Drift: ±0.02 µV/°C (max)
  • Gain Error: ±0.1% (max)
  • Gain Error Drift: ±25 ppm/°C (max)
  • Common Mode Rejection: 140 dB (min)
• Power Monitoring Accuracy
  • 0.7% full scale (–40°C to +125°C)
• Fast Alert Response: 75 µs
• Wide Common-Mode Range: –0.3 V to +85 V
• Bus Voltage Sense Input: 0 V to 85 V
• Shunt Full-Scale Differential Range: ±163.84 mV / ±40.96 mV
• Extremely Low Input Bias Current: 2.5 nA (max)
• Integrated Temperature Sensor: ±1°C accuracy (at 25°C)
• Programmable Conversion Time & Averaging
• High-Speed I2C Interface (2.94 MHz) with 16 Pin-Selectable Addresses
• Low-Power Operation
  • Supply Voltage: 2.7 V to 5.5 V
  • Operational Current: 640 µA (typ)
  • Shutdown Current: 5 µA (max)

Why Use the INA238?

1. Ultra-Low Offset & Drift
   Enables accurate measurements from micro-amps to kilo-amps without significant shunt power loss.
2. Wide Dynamic Range
   ±163.84 mV or ±40.96 mV full-scale input allows you to sense a broad range of current levels.
3. Built-In Power Calculations
   Automatically calculates current, voltage, temperature, and power—reducing microcontroller overhead.
4. High-Speed & Programmable
   Configure conversion times (50 µs to 4.12 ms) and averaging (1x to 1024x) for optimized noise vs. speed.

Getting Started

Installation

1. Using the Arduino IDE Library Manager

   • In the Arduino IDE, go to Sketch → Include Library → Manage Libraries...
   • Search for “Simple_INA238” and install the latest version.

2. Manual Installation

   • Download or clone this repository.
   • Move the Simple_INA238 folder into your Documents/Arduino/libraries directory.
   • Restart the Arduino IDE if it’s open.

Basic Usage

Here’s a quick example of how to initialize and read values from the INA238 using this library:

#include <Wire.h>
#include "Simple_Wire.h"
#include "Simple_INA238.h"

// Create an INA238 object
Simple_INA238 ina238;

// ESP32 Connection options:
#define SDA_PIN 14 // I am using an ESP32 and chose GPIO pin 14 for the I2C SDA connection
#define SCL_PIN 15 // I am using an ESP32 and chose GPIO pin 15 for the I2C SCL connection
// Arduino Uno Connection options:
//#define SDA_PIN A4 
//#define SCL_PIN A5

#define Shunt_Resistor_Value 0.002f // 0.002 ohms matching the INA-238 30A Breakout Board
#define Maximum_Expected_Current 25.5f // Amps 
#define DelayBetweenDisplayingReadings 1000 //ms
#define ina238Address 0x40

// your function that is called when readings are ready
void ShowReadings(){
  static int ReadingCount = 0;
  float current = ina238.Current();      // in Amps
  float voltage = ina238.VoltageBus();   // in Volts
  float power   = ina238.Power();        // in Watts
  float tempC    = ina238.Temperature();  // in °C (die temp)
  float tempF    = ina238.Temperature(true);  // in °F (die temp)
  Serial.print("\nReading# "); Serial.println(ReadingCount++);
  Serial.print("Current: "); Serial.print(current); Serial.println(" A");
  Serial.print("Voltage: "); Serial.print(voltage); Serial.println(" V");
  Serial.print("Power:   "); Serial.print(power);   Serial.println(" W");
  Serial.print("Temp:    "); Serial.print(tempC);    Serial.println(" °C");
  Serial.print("Temp:    "); Serial.print(tempF);    Serial.println(" °F");
}

void setup() {
  Serial.begin(115200);
  Serial.println(F("\n\nSimple_INA238 Volt Amp Meter"));

  if(!ina238.begin(SDA_PIN, SCL_PIN).SetAddress(ina238Address).Check_Address()){ // Comm Startup and Check
    Serial.println("Simple_INA238 failed to find device! \n !!! STOP !!!");
    while (1);
  }

// Simple_Config() uses the default settings of the INA238 and initializes the
// reading mode to trigger when Voltage and Current readings are complete
  ina238.Simple_Config(Maximum_Expected_Current,Shunt_Resistor_Value);

// When readings are ready call this function example "ShowReadings"
  ina238.setOnConversionReadyCallback(ShowReadings);
  Serial.println("INA238 initialized!");
}

void loop() {
// place the Alert() functin within your loop() functin to handle all the processes of the INA238 
// this has an optional non blocking delay that will skip checking until the timer has elapsed.
  ina238.Alert(DelayBetweenDisplayingReadings); // Callbacks are triggered withing this alert function
}

• ina238.begin(SDA_PIN, SCL_PIN).SetAddress(ina238Address).Check_Address(): Initializes the sensor at the specified I2C address and performs a connection test.
• Current(), VoltageBus(), Power(), Temperature(): High-level functions to retrieve sensor data.

Documentation

• Library Reference: Check out the inline comments in the source files for detailed usage and advanced configuration.
• INA238 Datasheet: For a deep dive into register definitions and electrical characteristics, see the official datasheet.

Contributing

1. Fork the repo on GitHub.
2. Create a feature branch for your changes (git checkout -b my-new-feature).
3. Commit your changes.
4. Open a Pull Request, describing what you’ve changed or added.

All contributions—bug reports, new features, and documentation improvements—are welcome!

License

This project is licensed under the MIT License. See the LICENSE file for details.

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Happy Measuring!

Enjoy using Simple_INA238 to accurately measure current, voltage, power, and temperature in your Arduino projects. If you have questions or run into issues, please open a GitHub issue, and we’ll be glad to help!