Input Devices

🐲 1. Project Overview

This week, I focused on using an input sensor with the custom board I previously designed. I chose the APDS-9960 sensor, which is capable of detecting color, proximity, gesture, and ambient light. It’s compact, powerful, and perfect for interactive applications.

I used the same Grove-style shield I created earlier — based on the XIAO ESP32C3 — which includes Grove connectors that make connecting sensors really easy without messy wiring. My goal was to plug in the APDS-9960, read values from it, and get a better understanding of how microcontrollers interact with physical sensor data.

🐲 2. Sensor Selection & Connection

I picked the APDS-9960 mainly for its multi-functional features, but for this week’s test I focused specifically on the color sensing capability.

- Proximity Detection
- Gesture Recognition
- Ambient & Color Sensing (used for this test)

I connected the sensor to one of the Grove ports on my board — since the APDS-9960 communicates using I2C, it routes SDA and SCL straight to the microcontroller without any extra setup. Before powering up, I quickly checked the wiring with a multimeter just to be safe.

🐲 3. Programming & Testing

For the code, I used the Arduino IDE and the SparkFun_APDS9960 library. I wrote a sketch to read red, green, blue, and clear light values and printed the results in the Serial Monitor — plus a little logic to guess what color the sensor was seeing based on RGB values.

💻 Example Code: APDS-9960 Color Sensor on XIAO ESP32C3

#include <Wire.h>
#include <SparkFun_APDS9960.h>

SparkFun_APDS9960 apds;

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

  if (!apds.init()) {
    Serial.println("APDS-9960 initialization failed!");
    while (1);
  }

  Serial.println("APDS-9960 Color Sensor Initialized.");
  apds.enableLightSensor(false); // RGB mode only
  delay(500); // Let sensor settle
}

void loop() {
  uint16_t r, g, b, c;

  if (apds.readRedLight(r) && apds.readGreenLight(g) && apds.readBlueLight(b) && apds.readAmbientLight(c)) {
    Serial.print("R: "); Serial.print(r);
    Serial.print("  G: "); Serial.print(g);
    Serial.print("  B: "); Serial.print(b);
    Serial.print("  Clear: "); Serial.print(c);

    String detectedColor = detectColor(r, g, b);
    Serial.print("  → Detected Color: ");
    Serial.println(detectedColor);
  } else {
    Serial.println("Error reading color values.");
  }

  delay(1000);
}

String detectColor(uint16_t r, uint16_t g, uint16_t b) {
  if (r > g && r > b) {
    if (r > 200 && g > 100 && b < 100) return "Orange/Yellow";
    return "Red";
  } else if (g > r && g > b) {
    if (g > 200 && r > 200) return "Yellow";
    return "Green";
  } else if (b > r && b > g) {
    return "Blue";
  } else if (r > 150 && g > 150 && b > 150) {
    return "White/Light";
  } else if (r < 50 && g < 50 && b < 50) {
    return "Black/Dark";
  } else {
    return "Unknown";
  }
}

This setup let me see the color data update live in the Serial Monitor, and it was a great way to understand how RGB intensity translates to human-readable color.

🐲 4. Results & Observations

Sensor Focus: I worked specifically with the color sensing function of the APDS-9960. During my testing, I observed that:

Red, Green, and Blue values changed dynamically based on the surface color placed in front of the sensor.
White surfaces reflected high readings across all three RGB channels.
Colored objects (like paper or plastic) showed dominant readings in their respective color bands.

Unexpected Behavior: One thing that stood out was that when I pointed the sensor into open air (i.e., "nothing"), it still returned a strong red reading.

This is likely due to:

- Internal IR reflections from the sensor's housing.
- Light scattering from particles in the air or nearby surfaces.
- The red channel being more sensitive to ambient reflections compared to others.

Easy Connectivity: Using the Grove connector made everything extremely convenient. No jumper wires, no breadboarding — just plug in the sensor, upload the code, and start testing.