7Semi INA240 Arduino Library

Arduino library for the Texas Instruments INA240 high-side current sense amplifier.

The INA240 is a precision bidirectional current-sense amplifier designed for motor control, power monitoring, battery management systems, and other applications requiring accurate current measurements in noisy environments.

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Features

• Supports INA240A1 (20 V/V Gain)

• Supports INA240A2 (50 V/V Gain)

• Supports INA240A3 (100 V/V Gain)

• Bidirectional current measurement

  • Positive and negative current detection

• Output voltage measurement

• Shunt voltage calculation

• Current calculation

• Automatic offset calibration

• Manual offset adjustment

• ADC averaging support

  • Reduces measurement noise

• Compatible with:

  • Arduino AVR
  • ESP32
  • ESP8266
  • RP2040
  • STM32
  • Any platform supporting analogRead()

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Connections / Wiring

The INA240 output is connected to an ADC-capable input pin.

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Typical Connection

INA240 Pin	MCU Connection	Notes
VS	3.3V / 5V	Device supply
GND	GND	Common ground
OUT	ADC Pin	Analog output
REF1/REF2	Optional	Offset reference for bidirectional sensing

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Bidirectional Current Measurement

For bidirectional current sensing:

VOUT = VREF + (VSHUNT × GAIN)

Where:

• VREF is typically VCC / 2
• Positive current increases output voltage
• Negative current decreases output voltage

The library supports:

• Automatic offset calibration
• Manual offset voltage configuration

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Installation

Arduino Library Manager

1. Open Arduino IDE
2. Open Library Manager
3. Search for 7Semi INA240
4. Click Install

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Manual Installation

1. Download repository ZIP
2. Arduino IDE → Sketch → Include Library → Add ZIP Library

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Library Overview

Initialize Sensor

INA240_7Semi sensor(
    A0,
    INA240_7Semi::INA240_A1,
    0.01f,
    5.0f,
    1023);

Parameters:

• ADC pin
• Gain variant
• Shunt resistor value
• ADC reference voltage
• Maximum ADC value

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Supported Gain Variants

INA240_7Semi::INA240_A1
INA240_7Semi::INA240_A2
INA240_7Semi::INA240_A3

Variant	Gain
INA240_A1	20
INA240_A2	50
INA240_A3	100

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Read ADC Value

uint16_t adc = sensor.readAnalog();

Returns averaged ADC reading.

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Read Output Voltage

float voltage = sensor.readVoltage();

Returns INA240 output voltage.

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Read Shunt Voltage

float shuntVoltage = sensor.readShuntVoltage();

Returns voltage across the shunt resistor after offset compensation.

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Read Current

float current = sensor.readCurrent();

Returns measured current in amperes.

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Automatic Calibration

sensor.calibrate();

Performs automatic offset calibration.

Run this with zero current flowing.

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Manual Offset Adjustment

sensor.setOffsetVoltage(2.500f);

Useful when REF is externally driven.

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Get Offset Voltage

float offset = sensor.getOffsetVoltage();

Returns stored offset voltage.

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Basic Example

#include <7Semi_INA240.h>

INA240_7Semi CurrentSensor(
    A0,
    INA240_7Semi::INA240_A1,
    0.01f,
    5.0f,
    1023);

void setup()
{
    Serial.begin(115200);

    Serial.println("INA240 Calibration");

    delay(2000);

    // Ensure zero current during calibration
    CurrentSensor.calibrate();

    Serial.print("Offset Voltage: ");
    Serial.println(CurrentSensor.getOffsetVoltage(), 4);
}

void loop()
{
    Serial.print("ADC: ");
    Serial.print(CurrentSensor.readAnalog());

    Serial.print(" | Vout: ");
    Serial.print(CurrentSensor.readVoltage(), 4);

    Serial.print(" V | Current: ");
    Serial.print(CurrentSensor.readCurrent(), 4);

    Serial.println(" A");

    delay(500);
}

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Applications

• Battery monitoring
• Motor current sensing
• Solar power systems
• DC power monitoring
• Power supply testing
• Robotics
• Industrial automation
• Energy measurement systems

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Notes

• Use an appropriate shunt resistor for your current range.
• For best accuracy, run offset calibration after power-up.
• ADC quality affects measurement resolution.
• ESP32 users may benefit from ADC calibration for improved accuracy.

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License

MIT License

Copyright (c) 7Semi