How to Use NAU7802 ADC Converter: Examples, Pinouts, and Specs

The NAU7802 24-Bit ADC by Adafruit is a high-precision, low-power analog-to-digital converter (ADC) designed for applications requiring accurate measurement of analog signals. It is particularly well-suited for weighing scales, load cells, and other precision measurement systems. The NAU7802 features a 24-bit resolution, an integrated programmable gain amplifier (PGA), and supports I2C communication, making it easy to interface with microcontrollers such as the Arduino UNO or Raspberry Pi.

• Weighing scales and load cell systems
• Industrial measurement systems
• Portable instrumentation
• IoT devices requiring precise analog signal measurement
• Sensor data acquisition

The following table outlines the key technical details of the NAU7802 ADC:

The NAU7802 ADC is available on a breakout board with the following pin configuration:

To use the NAU7802 ADC with an Arduino UNO, follow these steps:

1. Wiring:

   • Connect the VIN pin of the NAU7802 to the 5V pin on the Arduino.
   • Connect the GND pin of the NAU7802 to the GND pin on the Arduino.
   • Connect the SCL pin of the NAU7802 to the A5 pin on the Arduino (I2C clock line).
   • Connect the SDA pin of the NAU7802 to the A4 pin on the Arduino (I2C data line).

2. Install Required Libraries:

   • Install the Adafruit NAU7802 library from the Arduino Library Manager.

3. Example Code: Use the following example code to read data from the NAU7802:

   #include <Wire.h>
   #include <Adafruit_NAU7802.h>
   
   // Create an instance of the NAU7802 ADC
   Adafruit_NAU7802 nau7802;
   
   void setup() {
     Serial.begin(115200); // Initialize serial communication
     while (!Serial);      // Wait for the serial monitor to open
   
     // Initialize the NAU7802
     if (!nau7802.begin()) {
       Serial.println("Failed to find NAU7802 chip!");
       while (1); // Halt execution if the chip is not found
     }
     Serial.println("NAU7802 found!");
   
     // Calibrate the internal offset
     if (!nau7802.calibrateAFE()) {
       Serial.println("Failed to calibrate AFE!");
       while (1); // Halt execution if calibration fails
     }
     Serial.println("Calibration complete.");
   }
   
   void loop() {
     // Check if data is ready
     if (nau7802.available()) {
       // Read the raw ADC value
       int32_t adcValue = nau7802.read();
       Serial.print("ADC Value: ");
       Serial.println(adcValue);
     }
     delay(100); // Small delay for readability
   }
   

• Power Supply: Ensure the power supply voltage matches the operating range of the NAU7802 (2.7V to 5.5V for AVDD).
• I2C Pull-Up Resistors: The breakout board includes pull-up resistors for the I2C lines. If multiple I2C devices are connected, ensure the total pull-up resistance is appropriate.
• Calibration: Always perform an internal offset calibration (calibrateAFE()) before taking measurements to ensure accuracy.
• Load Cell Connection: When using the NAU7802 with a load cell, connect the load cell's excitation and signal lines to the appropriate pins on the breakout board.

1. The NAU7802 is not detected on the I2C bus:

   • Ensure the wiring is correct and matches the pin configuration.
   • Verify that the I2C address (default: 0x2A) is not conflicting with other devices on the bus.
   • Check the pull-up resistors on the I2C lines.

2. ADC readings are unstable or noisy:

   • Ensure proper grounding and shielding of the analog input signals.
   • Use a stable power supply to minimize noise.
   • Verify that the load cell or sensor is properly connected and calibrated.

3. Calibration fails:

   • Ensure the load cell or sensor is not under stress during calibration.
   • Verify that the power supply voltage is stable and within the specified range.

Q: Can I use the NAU7802 with a 3.3V microcontroller?
A: Yes, the NAU7802 supports a wide range of supply voltages (2.7V to 5.5V for AVDD). Ensure the I2C logic levels are compatible with your microcontroller.

Q: What is the maximum sampling rate of the NAU7802?
A: The NAU7802 supports a maximum sampling rate of 320 samples per second (SPS), depending on the selected gain and filter settings.

Q: How do I change the I2C address of the NAU7802?
A: The I2C address of the NAU7802 is fixed at 0x2A and cannot be changed. If multiple NAU7802 devices are needed, consider using an I2C multiplexer.

Q: Can I use the NAU7802 for non-weighing applications?
A: Yes, the NAU7802 can be used for any application requiring high-precision analog-to-digital conversion, such as sensor data acquisition or instrumentation.

By following this documentation, you can effectively integrate the NAU7802 ADC into your projects and achieve accurate, high-resolution measurements.