How to Use FDC1004: Examples, Pinouts, and Specs

The FDC1004 is a high-precision capacitance-to-digital converter (CDC) manufactured by Protocentral. It is designed to measure capacitance with exceptional accuracy and resolution, making it ideal for a wide range of sensing applications. The FDC1004 supports up to four measurement channels and features an integrated shield driver to minimize interference and noise, ensuring reliable performance in challenging environments.

• Proximity Sensing: Detecting the presence or absence of objects.
• Liquid Level Detection: Measuring liquid levels in tanks or containers.
• Touch Sensing: Implementing touch-sensitive interfaces.
• Environmental Monitoring: Measuring changes in capacitance due to environmental factors.
• Industrial Automation: Non-contact sensing for automation systems.

The FDC1004 is a versatile component with the following key technical details:

The FDC1004 is typically available in a 10-pin package. Below is the pinout and description:

The FDC1004 is straightforward to use in a circuit, but proper configuration and design considerations are essential for optimal performance.

1. Power Supply: Connect the VDD pin to a stable 3.0V to 3.6V power source and the GND pin to ground.
2. I²C Communication: Connect the SDA and SCL pins to the corresponding I²C lines of your microcontroller. Use pull-up resistors (typically 4.7 kΩ) on both lines.
3. Capacitance Measurement: Connect the capacitance to be measured to one of the CAPx pins (e.g., CAP1). If shielding is required, connect the SHLDx pin to the shield of the sensor.
4. Initialization: Configure the FDC1004 via I²C commands to set the measurement mode, channel, and other parameters.

• Shielding: Use the integrated shield driver (SHLDx pins) to reduce noise and interference in capacitive measurements.
• Offset Calibration: The FDC1004 supports offset calibration to account for parasitic capacitance in the system.
• I²C Address: The default I²C address of the FDC1004 is 0x50. Ensure no address conflicts if multiple devices are on the same bus.
• Bypass Capacitor: Place a 0.1 µF ceramic capacitor close to the VDD pin for power supply decoupling.

Below is an example of how to interface the FDC1004 with an Arduino UNO to measure capacitance on channel 1:

#include <Wire.h>

// FDC1004 I2C address
#define FDC1004_ADDRESS 0x50

// Registers for FDC1004
#define FDC1004_MEAS1_MSB 0x00  // Measurement 1 MSB register
#define FDC1004_MEAS1_LSB 0x01  // Measurement 1 LSB register

void setup() {
  Wire.begin(); // Initialize I2C communication
  Serial.begin(9600); // Initialize serial communication for debugging

  // Configure FDC1004 (example: set measurement mode for channel 1)
  Wire.beginTransmission(FDC1004_ADDRESS);
  Wire.write(0x08); // Configuration register for channel 1
  Wire.write(0x10); // Enable measurement on channel 1
  Wire.endTransmission();
}

void loop() {
  uint16_t capacitanceMSB, capacitanceLSB;
  float capacitance;

  // Request measurement data from FDC1004
  Wire.beginTransmission(FDC1004_ADDRESS);
  Wire.write(FDC1004_MEAS1_MSB); // Point to MSB register
  Wire.endTransmission();
  Wire.requestFrom(FDC1004_ADDRESS, 2); // Request 2 bytes (MSB + LSB)

  if (Wire.available() == 2) {
    capacitanceMSB = Wire.read(); // Read MSB
    capacitanceLSB = Wire.read(); // Read LSB
    capacitance = ((capacitanceMSB << 8) | capacitanceLSB) * 0.000244; 
    // Convert to pF (example scaling factor)
    Serial.print("Capacitance: ");
    Serial.print(capacitance);
    Serial.println(" pF");
  }

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

• The scaling factor (0.000244) is an example and may need adjustment based on your configuration.
• Ensure proper pull-up resistors are connected to the SDA and SCL lines.

1. No I²C Communication:

   • Ensure the SDA and SCL lines are correctly connected to the microcontroller.
   • Verify that pull-up resistors are present on the I²C lines.
   • Check the I²C address of the FDC1004 (default is 0x50).

2. Inaccurate Capacitance Measurements:

   • Verify that the shield driver (SHLDx) is properly connected to reduce noise.
   • Perform offset calibration to account for parasitic capacitance.
   • Ensure the sensor is not exposed to excessive environmental noise.

3. Device Not Responding:

   • Confirm that the power supply voltage is within the specified range (3.0V to 3.6V).
   • Check for loose or incorrect connections.

Q: Can the FDC1004 measure negative capacitance?
A: No, the FDC1004 measures capacitance in the range of ±15 pF with an offset of up to 100 pF.

Q: What is the maximum I²C clock speed supported?
A: The FDC1004 supports I²C clock speeds up to 400 kHz (Fast Mode).

Q: Can I use all four channels simultaneously?
A: Yes, the FDC1004 can measure capacitance on up to four channels, but measurements are taken sequentially.

Q: How do I reduce noise in my measurements?
A: Use the integrated shield driver (SHLDx pins) and ensure proper grounding and shielding in your circuit design.