Getting Started with the ProtoCentral FDC1004 Capacitance Sensor Breakout Board

Introduction

The ProtoCentral FDC1004 breakout board uses the Texas Instruments FDC1004 capacitance-to-digital converter to measure tiny changes in capacitance with femtofarad-level resolution. This makes it ideal for non-contact applications like proximity sensing, liquid level detection through tank walls, and touch interfaces — all without requiring direct contact with the target.

The board connects to any Arduino or ESP32 via I2C (just 4 wires), includes an onboard 3.3V regulator, and supports up to 4 independent capacitance measurement channels.

This guide walks you through connecting the board, installing the Arduino library, and taking your first capacitance reading.

Key Features

• Texas Instruments FDC1004 capacitance-to-digital converter
• 4 independent measurement channels (CIN1–CIN4)
• Measurement range: ±15 pF with up to 100 pF offset capacitance
• Resolution: 0.5 fF (femtofarads)
• Output data rate: up to 400 samples per second
• I2C interface (address: 0x50)
• Onboard 3.3V voltage regulator — connect directly to 5V Arduino boards
• Compact breakout with standard 2.54mm headers

What’s in the Box

• 1x ProtoCentral FDC1004 breakout board (assembled and tested)
• Header pins (if not pre-soldered)

You will also need an Arduino Uno (or compatible board), jumper wires, and a USB cable.

Pin Connections

FDC1004 Breakout to Arduino Uno

Note: The FDC1004 breakout has an onboard 3.3V regulator, so you can safely connect Vcc to the Arduino’s 5V pin. The I2C pull-up resistors are included on the board.

Wiring Diagram

FDC1004 Breakout to ESP32

Tip: The ESP32 has multiple I2C buses. The library supports selecting an alternate bus (e.g., Wire1) — see the Advanced Usage section below.

Capacitance Input Channels

The board exposes four capacitance input channels: CIN1, CIN2, CIN3, and CIN4. Each channel measures the capacitance between its input pin and ground. For a basic reading, connect your sensing element (a copper pad, wire, or probe) to CIN1.

Installing the Arduino Library

Option 1: Arduino Library Manager (Recommended)

1. Open the Arduino IDE
2. Go to Sketch → Include Library → Manage Libraries…
3. In the search box, type “Protocentral FDC1004”
4. Find “ProtoCentral FDC1004 Capacitive Sensor Library” and click Install

Option 2: Manual Installation from GitHub

1. Go to github.com/Protocentral/ProtoCentral_fdc1004_breakout
2. Click Code → Download ZIP
3. In the Arduino IDE, go to Sketch → Include Library → Add .ZIP Library…
4. Select the downloaded ZIP file

Your First Reading

Open the basic example from the library:

File → Examples → ProtoCentral FDC1004 → Measure Raw Capacitance

This example initializes the FDC1004 at 100 samples per second, reads channel 1, and outputs the raw capacitance value over serial.

#include <Wire.h>
#include <Protocentral_FDC1004.h>

FDC1004 sensor(FDC1004_RATE_100HZ);

#define CHANNEL 0    // CIN1 (channels are 0-indexed: 0=CIN1, 1=CIN2, etc.)

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

    Wire.begin();
    sensor.begin();

    Serial.println("ProtoCentral FDC1004 - Capacitance Measurement");
    Serial.println("-----------------------------------------------");
}

void loop() {
    // Configure measurement on channel 0 (CIN1) vs CAPDAC
    sensor.configureMeasurementSingle(FDC1004_MEAS1, CHANNEL, FDC1004_CAPDAC);

    // Trigger a single measurement
    sensor.triggerSingleMeasurement(FDC1004_MEAS1, FDC1004_RATE_100HZ);

    delay(15);   // Wait for conversion to complete

    // Read the result
    uint16_t value[2];
    if (sensor.readMeasurement(FDC1004_MEAS1, value) == 0) {
        // Convert raw value to capacitance in pF
        int32_t capacitance = ((int32_t)(int16_t)value[0]) << 8;
        capacitance |= (value[1] >> 8);

        float capPf = (float)capacitance / 524288.0;  // Convert to pF

        Serial.print("Capacitance: ");
        Serial.print(capPf, 3);
        Serial.println(" pF");
    }

    delay(200);
}

What to Expect

After uploading the sketch and opening the Serial Monitor at 115200 baud, you should see output like:

ProtoCentral FDC1004 - Capacitance Measurement
-----------------------------------------------
Capacitance: 0.234 pF
Capacitance: 0.231 pF
Capacitance: 0.228 pF

With nothing connected to CIN1, you will see a small baseline capacitance from the PCB traces. Bring your finger close to the CIN1 pin (without touching it) and you should see the value increase — this is proximity detection in action.

Advanced: Using Multiple I2C Buses

On boards with multiple I2C ports (ESP32, Arduino Mega), you can specify an alternate bus:

// Use Wire1 instead of Wire
FDC1004 sensor(&Wire1, FDC1004_RATE_100HZ);

void setup() {
    Wire1.begin(25, 26);  // SDA=GPIO25, SCL=GPIO26 on ESP32
    sensor.begin();
}

Troubleshooting

No readings / I2C device not found

• Double-check SDA and SCL wiring (these are the most common mistake)
• Verify Vcc is connected to 5V (Arduino) or 3.3V (ESP32) and GND to GND
• Run an I2C scanner sketch — the FDC1004 should appear at address 0x50
• If using an ESP32 with custom pins, make sure Wire.begin(SDA_PIN, SCL_PIN) matches your wiring

Readings are stuck at zero

• Ensure you are calling triggerSingleMeasurement() before readMeasurement()
• Check that the delay between trigger and read is at least 15ms
• Verify the channel number matches where your sensing element is connected (channels are 0-indexed)

Readings are very noisy

• Keep wires short between the board and sensing element
• Shield the sensing wire if possible (connect shield to GND)
• Increase the averaging by taking multiple readings and computing the mean
• Ensure the sensing element is not physically vibrating

Readings are saturated (stuck at max)

• The capacitance on the channel may exceed the ±15 pF measurement range
• Reduce the area of your sensing element or increase the distance to the target
• Check for a short circuit on the capacitance input pins

Resources

• Arduino Library on GitHub
• FDC1004 Datasheet (TI)
• Hardware Design Files (Schematic + Board)

License

• Hardware: Creative Commons Share-alike 4.0 International (CC BY-SA 4.0)
• Software / Library: MIT License
• Documentation: Creative Commons Share-alike 4.0 International (CC BY-SA 4.0)