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This guide walks through setting up your ESP32 development board for the S-Parking system.

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Prerequisites

Before starting, ensure you have:
  • ESP32 development board (NodeMCU-32S or similar)
  • Arduino IDE 1.8.x or 2.x
  • USB cable (usually USB-A to Micro-USB)
  • WiFi network with 2.4 GHz support (ESP32 doesn’t support 5 GHz)

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Arduino IDE Configuration

1

Install ESP32 Board Support

Add the ESP32 board manager URL:
  1. Open Arduino IDE
  2. Go to File → Preferences
  3. Add this URL to “Additional Board Manager URLs”:
https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json
  1. Go to Tools → Board → Boards Manager
  2. Search for “esp32” and install “esp32 by Espressif Systems”
2

Install Required Libraries

Install these libraries via Sketch → Include Library → Manage Libraries:
  • Adafruit VL53L0X (for sensor communication)
  • ArduinoJson (for JSON parsing)
  • HTTPClient (usually pre-installed with ESP32 core)
Make sure to install ArduinoJson version 6.x, not 7.x. The firmware uses v6 API.
3

Select Board and Port

In the Arduino IDE:
  • Board: Tools → Board → ESP32 Arduino → “ESP32 Dev Module” or your specific board
  • Port: Tools → Port → Select the COM/USB port where your ESP32 is connected
  • Upload Speed: 115200 (can be increased to 921600 for faster uploads)

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WiFi Configuration

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Creating secrets.h File

The firmware uses a arduino_secrets.h file to store sensitive credentials. This file is not committed to version control.
1

Copy the Example File

Navigate to workspace/source/firmware/S-Parking/ and copy:
cp arduino_secrets.example.h arduino_secrets.h
2

Edit Configuration

Open arduino_secrets.h and fill in your actual values:
#pragma once

// --- WiFi Credentials ---
#define SECRET_SSID "YourWiFiNetwork"
#define SECRET_PASS "YourWiFiPassword"

// --- Google Cloud URLs ---
#define SECRET_GCP_URL_INGEST "https://your-ingest-url.run.app"
#define SECRET_GCP_URL_GET "https://your-get-status-url.run.app"

// --- Spot Identification ---
#define SECRET_SPOT_ID "A-01"

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Configuration Parameters

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SECRET_SSID
string
required
Your WiFi network name (SSID). Must be a 2.4 GHz network.
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SECRET_PASS
string
required
WiFi password for authentication.
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SECRET_GCP_URL_INGEST
string
required
Cloud Run URL for the ingest-parking-data function. Used to send sensor status updates.
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SECRET_GCP_URL_GET
string
required
Cloud Run URL for the get-parking-status function. Used to retrieve reservation status.
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SECRET_SPOT_ID
string
required
Unique identifier for this parking spot (e.g., “A-01”, “B-12”). Must match the spot ID in your Firestore database.
Never commit arduino_secrets.h to version control! It contains sensitive credentials.The .gitignore should include:
arduino_secrets.h

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WiFi Connection Logic

The firmware implements robust WiFi connection from S-Parking.ino:205-228: 
void connectToWiFi() {
  Serial.print("Conectando a WiFi: ");
  Serial.println(ssid);
  
  WiFi.mode(WIFI_STA); // Station mode
  WiFi.begin(ssid, password);
  
  int intentos = 0;
  while (WiFi.status() != WL_CONNECTED && intentos < 20) {
    delay(500);
    Serial.print(".");
    intentos++;
  }
  
  if (WiFi.status() == WL_CONNECTED) {
    Serial.println("\n¡WiFi Conectado!");
    Serial.print("IP asignada: ");
    Serial.println(WiFi.localIP());
  } else {
    Serial.println("\nFallo al conectar WiFi. Reiniciando...");
    delay(1000);
    ESP.restart(); // Auto-restart on failure
  }
}

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Connection Behavior

  • Retry Logic: Attempts connection 20 times (10 seconds total)
  • Auto-Restart: If connection fails, ESP32 restarts automatically
  • Station Mode: Uses WIFI_STA mode (not AP mode)
  • Serial Feedback: Prints connection status to Serial Monitor at 115200 baud

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Flashing Firmware

1

Open the Project

In Arduino IDE, open S-Parking/S-Parking.ino
2

Verify Configuration

Ensure arduino_secrets.h exists and contains valid credentials.
3

Compile and Upload

  1. Click the Verify button (checkmark) to compile
  2. Fix any compilation errors
  3. Click the Upload button (arrow) to flash
  4. Wait for “Done uploading” message
4

Monitor Serial Output

Open Serial Monitor (Tools → Serial Monitor) at 115200 baud:
Conectando a WiFi: YourNetwork
...........
¡WiFi Conectado!
IP asignada: 192.168.1.42
Cambio físico detectado: 1
Enviado a ingest. Codigo: 200
Sincronizando. Local: 1 | Nube: 1

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Common Upload Issues

  • Windows: Install CP210x or CH340 USB drivers
  • macOS: Driver usually automatic, check System Report → USB
  • Linux: Add user to dialout group: sudo usermod -a -G dialout $USER
  • Hold the BOOT button while clicking Upload
  • Try reducing upload speed to 115200
  • Check USB cable (some cables are power-only)
  • Power supply insufficient (use USB 3.0 port or powered hub)
  • Reduce WiFi power: Add WiFi.setTxPower(WIFI_POWER_19_5dBm); after WiFi.begin()
  • Verify SSID and password are correct
  • Ensure 2.4 GHz WiFi (not 5 GHz)
  • Check if network has MAC filtering or captive portal
  • Move ESP32 closer to router during testing

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Secrets Structure Reference

The arduino_secrets.h file structure: 
#pragma once

// --- CREDENCIALES WIFI ---
#define SECRET_SSID "NOMBRE_DE_TU_WIFI"
#define SECRET_PASS "PASSWORD_DE_TU_WIFI"

// --- TUS URLs DE GOOGLE CLOUD ---

// 1. URL para ENVIAR datos (ingest-parking-data)
#define SECRET_GCP_URL_INGEST "https://tu-url-ingest.run.app"

// 2. URL para LEER estado (get-parking-status)
// NOTA: Esta funcion devuelve TODOS los puestos.
// El ESP32 buscará su ID en la lista.
#define SECRET_GCP_URL_GET "https://tu-url-get-status.run.app"

// 3. Identificación del Puesto
#define SECRET_SPOT_ID "A-01"
The GET endpoint returns all parking spots. The ESP32 searches the JSON array for its specific spot_id. Make sure the ID matches exactly (case-sensitive).

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Testing Connectivity

After flashing, verify the system works:
  1. Check Serial Monitor for WiFi connection confirmation
  2. Verify LED lights up green (if no car present)
  3. Place hand over sensor - LED should turn red immediately
  4. Check cloud logs in GCP console for incoming requests
  5. Monitor state synchronization every 15 seconds
Expected Serial output: 
Conectando a WiFi: MyNetwork
...
¡WiFi Conectado!
IP asignada: 192.168.1.100
Cambio físico detectado: 1
Enviado a ingest. Codigo: 200
Sincronizando. Local: 1 | Nube: 1

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Next Steps

Sensor Calibration

Calibrate distance thresholds for accurate detection

LED Indicators

Wire and configure RGB LED indicators

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