Proximity LED Display — Seeed XIAO ESP32-C3

A PlatformIO project that reads distance from an HC-SR04 ultrasonic sensor and lights a 5-LED NeoPixel strip to show how close an object is. The colour changes from green → yellow → red as the object gets farther away.

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Hardware Required

Component	Quantity
Seeed Studio XIAO ESP32-C3	1
HC-SR04 Ultrasonic Distance Sensor	1
WS2812B NeoPixel Strip (5 LEDs)	1
USB-C cable	1
Breadboard + jumper wires	—

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Wiring

Ultrasonic Sensor (HC-SR04)

HC-SR04 Pin	XIAO ESP32-C3 Pin
VCC	5V
GND	GND
TRIG	D3 (GPIO 5)
ECHO	D2 (GPIO 4)

Note: The HC-SR04 echo line outputs 5 V. The ESP32-C3 GPIO is 3.3 V tolerant only. Use a voltage divider (two resistors: 1 kΩ and 2 kΩ) or a logic-level shifter on the ECHO line to protect the microcontroller.

NeoPixel Strip

NeoPixel Pin	XIAO ESP32-C3 Pin
5V / VCC	5V
GND	GND
DIN (Data In)	D10 (GPIO 10)

Power the strip from the USB 5 V rail for up to ~5 LEDs at moderate brightness. For longer strips, use a separate 5 V supply with a shared ground.

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LED Behaviour

Distance from sensor	LEDs lit	Colour
0 – 2 cm	1	Green
2 – 4 cm	2	Yellow
4 – 6 cm	3	Red
6 – 8 cm	4	Red
> 8 cm	5	Red
Out of range / no echo	0 (all off)	—

The closer the object, the fewer LEDs glow — think of it as a reverse proximity warning bar.

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Software Setup

1. Install PlatformIO

• VS Code: Install the PlatformIO IDE extension.
• CLI only: pip install platformio

2. Clone this repository

git clone https://github.com/SanchakGarg/YSP-Electronics-Session-2026.git
cd YSP-Electronics-Session-2026

3. Open in PlatformIO

• VS Code: File → Open Folder → select the cloned folder. PlatformIO detects platformio.ini automatically.
• CLI: no extra steps needed.

4. Build & Upload

VS Code: Click the Upload button (right-arrow icon) in the PlatformIO toolbar at the bottom.

CLI:

pio run --target upload

PlatformIO will automatically download the espressif32 platform and the Adafruit NeoPixel library on first build.

5. Open Serial Monitor

VS Code: Click the plug icon in the PlatformIO toolbar.

CLI:

pio device monitor

Baud rate: 115200. You will see live distance readings printed every 100 ms.

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Project Structure

YSP-Electronics-Session-2026/
├── platformio.ini   # Board, framework, and library configuration
├── src/
│   └── main.cpp     # All application logic
└── README.md        # This guide

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How It Works

1. Trigger pulse — The code sends a 10 µs HIGH pulse on the TRIG pin.
2. Echo measurement — pulseIn() measures how long the ECHO pin stays HIGH.
3. Distance formula — distance (cm) = duration (µs) × 0.034 / 2
   (speed of sound ≈ 340 m/s; divide by 2 for round trip).
4. LED mapping — The distance is compared against 2 cm thresholds; showLEDs(count, colour) clears the strip and sets the correct number of pixels.

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Troubleshooting

Problem	Likely cause	Fix
LEDs don't light up	Wrong data pin / no 5 V	Check wiring; confirm D10 is the data line
Distance always -1	Sensor not connected or ECHO pin wired wrong	Verify HC-SR04 wiring and 5 V supply
ESP32-C3 resets randomly	Strip drawing too much current from USB	Lower setBrightness() or use external 5 V supply
Readings jump around	Object too close (<2 cm) or angled surface	Keep sensor flat; minimum reliable range is ~2 cm

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License

MIT — free to use for education and personal projects.