Firebase Cloud Functions

Relevant source files

The following files were used as context for generating this wiki page:

• HomeSecurity/README.md
• HomeSecurity/src/firebase_notifier.cpp
• HomeSecurity/include/firebase_notifier.h
• HomeSecurity/src/motion_logic.cpp
• HomeSecurity/src/main.cpp

The Firebase Cloud Function serves as a serverless backend component in the HomeSecurity system. Its primary role is to act as a secure gateway between the ESP32 microcontroller and the Firebase Cloud Messaging (FCM) service. Instead of the ESP32 communicating directly with FCM, it sends a simple HTTP request to the Cloud Function, which then orchestrates the delivery of a push notification to the user's Android device.

This serverless architecture simplifies the logic on the ESP32, offloads authentication and complex API interactions to the cloud, and enhances security by abstracting away sensitive service credentials from the edge device.

Sources: HomeSecurity/README.md:29-53, 303-311

System Architecture

The Cloud Function is a critical component of the Cloud Tier, bridging the Edge Tier (ESP32) and the Client Tier (Android App). The ESP32 does not directly send push notifications; it triggers the Cloud Function, which in turn uses FCM to deliver the alert.

This diagram illustrates the notification data flow from the ESP32 to the mobile application.

ESP32 Implementation

On the ESP32, interaction with the Firebase Cloud Function is managed by the FirebaseNotifier class. This class encapsulates the logic for making secure HTTP POST requests to the function's endpoint.

Sources: HomeSecurity/include/firebase_notifier.h, HomeSecurity/src/firebase_notifier.cpp

FirebaseNotifier Class

The FirebaseNotifier class provides a straightforward interface for sending notifications.

This class diagram shows the structure of the FirebaseNotifier class.

Configuration

The FirebaseNotifier is instantiated in motion_logic.cpp with a hardcoded URL for the deployed Cloud Function. The FCM token for the target device is also hardcoded in this file.

// File: HomeSecurity/src/motion_logic.cpp

FirebaseNotifier notifier("https://trimitenotificare-k4cqa7es6q-uc.a.run.app");

const char* fcmToken = "d-OlFNUNSaSStUUsL05ofB:APA91bEd8ifGV-IIX15CJZHAbQovskC4MzL32mM5iDDON5GwLeoFdeWnYgYar0-lrmNf4lxb0AK54yycQB8TD_DMpMU4LOOp-UwBM_8Bi4DTAi1pYVpuNbA";

Sources: HomeSecurity/src/motion_logic.cpp:4, 7

HTTP Request Logic

The sendNotification method constructs and sends the HTTP request.

1. It establishes a secure connection using WiFiClientSecure. Note that it uses client.setInsecure() which is not recommended for production environments.
2. It initializes an HTTPClient instance with the function URL.
3. It sets the Content-Type header to application/json.
4. It constructs a JSON payload containing the notification title, body, and the device token.
5. It sends the payload via an HTTP POST request.
6. It returns true if the HTTP response code is 200 (OK), indicating success.

// File: HomeSecurity/src/firebase_notifier.cpp

bool FirebaseNotifier::sendNotification(const String& title, const String& body, const String& token) {
    WiFiClientSecure client;
    client.setInsecure(); // ⚠️ folosește cu grijă în producție

    HTTPClient https;
    if (!https.begin(client, url)) {
        // ... error handling
        return false;
    }

    https.addHeader("Content-Type", "application/json");

    String jsonPayload = "{\"title\":\"" + title + "\",\"body\":\"" + body + "\",\"token\":\"" + token + "\"}";

    int httpCode = https.POST(jsonPayload);

    if (httpCode > 0) {
        // ... success handling
        return (httpCode == 200);
    } else {
        // ... error handling
        return false;
    }
}

Sources: HomeSecurity/src/firebase_notifier.cpp:6-28

Payload Structure

The HTTP POST request sent to the Cloud Function contains a JSON body with the following structure:

Field	Type	Description
title	String	The title of the push notification.
body	String	The main content/message of the notification.
token	String	The FCM registration token of the target device.

Sources: HomeSecurity/src/firebase_notifier.cpp:16, HomeSecurity/README.md:313-317

Notification Triggers

Notifications are triggered from two separate FreeRTOS tasks based on sensor events, implementing a two-stage alert system.

Sources: HomeSecurity/src/main.cpp:12-13, HomeSecurity/src/motion_logic.cpp

Stage 1: Initial Alert

The possibleHumanMovementDetectedTask sends an initial warning notification when either the PIR sensor or the Hall effect sensor is triggered.

• Title: "Mișcare detectată"
• Body: "Sistemul a detectat o posibilă mișcare umană."

Sources: HomeSecurity/src/motion_logic.cpp:73-77

Stage 2: Confirmed Alert

The handleRadarMovementTask sends a confirmation notification if the microwave radar sensor detects continuous movement for more than 2 seconds.

• Title: "Mișcare confirmată"
• Body: "Radarul a detectat o mișcare continuă."

Sources: HomeSecurity/src/motion_logic.cpp:111-115

Sequence Diagram

This diagram shows the sequence of events when a PIR or Hall sensor triggers an initial alert.

Summary

The Firebase Cloud Function is a vital architectural element that decouples the ESP32 from the complexities of the Firebase Cloud Messaging service. It provides a simple, scalable, and secure HTTP endpoint for the embedded device to trigger push notifications. This design keeps the device-side code minimal and delegates the responsibility of notification delivery to a robust, serverless cloud environment.

Sources: HomeSecurity/README.md:29-53, 303-311