How to Use Qwiic Scale: Examples, Pinouts, and Specs

The Qwiic Scale is a digital weight measurement module designed by SparkFun, featuring the NAU7802 analog-to-digital converter (ADC). This component is part of the Qwiic Connect System, which simplifies integration with microcontrollers by using a standardized I2C interface. The Qwiic Scale is ideal for applications requiring precise weight measurements, such as kitchen scales, industrial weighing systems, robotics, and IoT projects.

With its high-resolution ADC and easy-to-use interface, the Qwiic Scale enables accurate and reliable weight sensing in a compact form factor. Its plug-and-play design makes it accessible for both beginners and advanced users.

Below are the key technical details of the Qwiic Scale:

The Qwiic Scale uses the Qwiic connector for I2C communication. It also includes breakout pins for additional flexibility. Below is the pin configuration:

1. Hardware Setup:

   • Connect the Qwiic Scale to your microcontroller using a Qwiic cable.
   • If using a load cell, connect its wires to the AIN+ and AIN- pins on the Qwiic Scale.
   • Ensure the microcontroller operates at 3.3V logic levels to match the Qwiic Scale.

2. Software Setup:

   • Install the SparkFun NAU7802 library for Arduino from the Arduino Library Manager.
   • Include the library in your Arduino sketch to communicate with the Qwiic Scale.

Below is an example Arduino sketch to read weight data from the Qwiic Scale:

#include <Wire.h>
#include <SparkFun_Qwiic_Scale_NAU7802_Arduino_Library.h>

// Create an instance of the NAU7802 class
NAU7802 myScale;

void setup() {
  Serial.begin(9600); // Initialize serial communication
  while (!Serial);    // Wait for the serial port to connect

  Serial.println("Qwiic Scale Example");

  // Initialize the Qwiic Scale
  if (!myScale.begin()) {
    Serial.println("Failed to find Qwiic Scale. Check connections.");
    while (1); // Halt if initialization fails
  }

  Serial.println("Qwiic Scale initialized!");

  // Calibrate the scale
  if (!myScale.calibrateAFE()) {
    Serial.println("Failed to calibrate the scale.");
    while (1); // Halt if calibration fails
  }

  Serial.println("Scale calibrated. Ready to measure weight.");
}

void loop() {
  // Read the raw ADC value
  long rawValue = myScale.getReading();
  Serial.print("Raw ADC Value: ");
  Serial.println(rawValue);

  // Convert the raw value to weight (requires calibration for accuracy)
  float weight = myScale.getWeight();
  Serial.print("Weight: ");
  Serial.print(weight);
  Serial.println(" grams");

  delay(1000); // Wait 1 second before the next reading
}

• Calibration: For accurate weight measurements, calibrate the scale with a known weight using the calibrateScale() function in the library.
• Power Supply: Ensure a stable 3.3V power supply to avoid noise in the ADC readings.
• Load Cell Wiring: Connect the load cell wires securely to avoid inconsistent readings.

1. Qwiic Scale Not Detected:

   • Ensure the Qwiic cable is securely connected.
   • Verify the I2C address (default: 0x2A) matches the address in your code.
   • Check that the microcontroller operates at 3.3V logic levels.

2. Inaccurate Weight Readings:

   • Perform a proper calibration with a known weight.
   • Ensure the load cell is not under physical stress or improperly mounted.

3. No Data from the Scale:

   • Verify the DRDY pin is functioning if used for interrupts.
   • Check the power supply voltage and connections.

Q: Can I use the Qwiic Scale with a 5V microcontroller?
A: The Qwiic Scale operates at 3.3V logic levels. If using a 5V microcontroller, use a logic level shifter to prevent damage.

Q: How do I change the I2C address?
A: The I2C address can be changed by modifying the address in the library code or using the setI2CAddress() function.

Q: What is the maximum weight the Qwiic Scale can measure?
A: The maximum weight depends on the load cell used. Refer to the load cell's datasheet for its capacity.

Q: Can I use multiple Qwiic Scales on the same I2C bus?
A: Yes, but each scale must have a unique I2C address. Configure the address using the library functions.

By following this documentation, you can effectively integrate the Qwiic Scale into your projects for precise weight measurement.