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The S-Parking system uses ESP32 microcontrollers paired with VL53L0X time-of-flight sensors and RGB LEDs to create intelligent parking space monitors.

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Hardware Components

Each parking sensor unit consists of:
1

ESP32 Development Board

The main microcontroller that handles:
  • WiFi connectivity to backend services
  • Sensor data processing
  • LED control logic
  • State synchronization with cloud
2

VL53L0X Time-of-Flight Sensor

Laser-based distance sensor that:
  • Measures distances up to 2000mm
  • Uses I2C communication protocol
  • Provides accurate occupancy detection
  • Low power consumption
3

RGB LED (Common Anode)

Visual indicator showing:
  • Red: Space occupied
  • Green: Space available
  • Amber: Space reserved (red + green)

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ESP32 Specifications

The firmware is designed for ESP32 boards with the following requirements:
FeatureSpecification
CPUDual-core Tensilica LX6
WiFi802.11 b/g/n (2.4 GHz)
GPIO PinsMinimum 3 required for LED
I2CRequired for VL53L0X sensor
Flash4MB recommended
Operating Voltage3.3V

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Pin Configuration

The default pin configuration from S-Parking.ino:9-11: 
#define LED_RED_PIN 13
#define LED_GREEN_PIN 12
#define LED_BLUE_PIN 14
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LED_RED_PIN
GPIO
default:"13"
GPIO pin for red LED channel (common anode, active LOW)
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LED_GREEN_PIN
GPIO
default:"12"
GPIO pin for green LED channel (common anode, active LOW)
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LED_BLUE_PIN
GPIO
default:"14"
GPIO pin for blue LED channel (reserved, not used for amber)

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Sensor Types

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VL53L0X Time-of-Flight Sensor

The Adafruit VL53L0X sensor uses laser-based ToF technology: Technical Specifications:
  • Range: 30mm to 2000mm
  • Accuracy: ±3% at typical distances
  • Interface: I2C (address 0x29)
  • Voltage: 2.6V to 3.5V
  • Field of View: 25°
Why Time-of-Flight?
  • More accurate than ultrasonic sensors
  • Not affected by object color or reflectivity
  • Fast measurement cycle (500ms in our implementation)
  • Reliable in various lighting conditions

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LED Indicators

The system uses a common anode RGB LED with inverted logic:

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Color States

setColor(1, 0, 0); // Physical car detected

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State Priority Logic

From S-Parking.ino:173-191, the LED update logic follows this priority:
  1. Physical presence overrides everything - If sensor detects a car, show RED
  2. Reservation status - If no car but cloud shows reserved (status=2), show AMBER
  3. Available - If no car and no reservation, show GREEN
void updateLEDs() {
  // 1. Maximum Priority: Physical car present = RED
  if (estadoLocalSensor == 0) {
    setColor(1, 0, 0); // Red
    return;
  }

  // 2. Check cloud for reservation
  if (estadoNube == 2) {
    setColor(1, 1, 0); // Amber (Red + Green)
    return;
  }

  // 3. No car, no reservation = GREEN
  setColor(0, 1, 0); // Green (Available)
}
The LED uses common anode configuration, meaning the logic is inverted:
  • LOW (0V) turns the LED ON
  • HIGH (3.3V) turns the LED OFF
The setColor() function handles this inversion automatically.

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Timing and Intervals

The firmware uses two timing loops from S-Parking.ino:30-31:
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sensorInterval
milliseconds
default:"500"
Sensor reading frequency - checked every 0.5 seconds for immediate response when cars park
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cloudPollInterval
milliseconds
default:"15000"
Cloud synchronization frequency - checked every 15 seconds for reservation updates
Why different intervals?
  • Fast sensor reads ensure immediate red light when cars arrive
  • Slower cloud polls reduce network traffic and API costs
  • This asymmetric design balances responsiveness with efficiency

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Next Steps

ESP32 Setup

Configure your ESP32 and flash the firmware

Sensor Calibration

Calibrate VL53L0X sensors and set distance thresholds

LED Indicators

Wire and configure RGB LED indicators

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