❄️ How We Cut IoT Backend Calls by 85% with C++ and BLE Pairing on ESP32

Project Snowman is an embedded IoT system built on an ESP32. Our goal?

Collect real-time environmental data, send it to the cloud, and display it on a live frontend —

all while minimizing backend strain and keeping config secure.

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🔧 Hardware & Stack

• ESP32
• DS18B20 temperature sensors
• C++ with PlatformIO
• BLE + Wi-Fi
• REST API (Render backend)
• React + Vite frontend (Netlify)

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🧱 Modular C++ Architecture (S.O.L.I.D. Principles)

We designed the firmware using modern object-oriented programming:

• SensorManager handles DS18B20 readings
• WiFiManager connects to Wi-Fi and checks status
• BLEServerModule handles proximity-based setup
• APIClient pushes data only when requested

if (bleTriggeredReconnect && millis() - bleReconnectTime > 10000) {
  WiFi.begin(bleSSID.c_str(), blePassword.c_str());
  bleServer->stopAdvertising();
}

Each class has a single responsibility — easy to debug, maintain, and scale.

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🔐 BLE Pairing Mode with Proximity Logic

BLE is used for configuration. No insecure web portals.

• BLE GATT server activates only during setup mode
• Accepts Wi-Fi credentials from a phone
• Reconnects automatically and turns off BLE afterward

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⚙️ Request-Only Backend API Flow

Instead of pushing sensor data continuously, the ESP32 sends updates only when requested by the frontend.

• Dropped backend calls from 100+ per hour ➝ ~15
• Reduced bandwidth, power, and compute costs

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💻 Frontend Integration (React + Vite)

The frontend fetches sensor data and renders it in real-time using stat cards.

useEffect(() => {
  fetch("/api/data/latest")
    .then(res => res.json())
    .then(setData);
}, []);

Fast. Clean. Minimal load.

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🧠 What We Learned

• Event-driven IoT logic beats constant loop polling
• BLE provisioning improves security + UX
• PlatformIO and C++ OOP scale beautifully for embedded builds

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🔜 What’s Next

• Audit logging for BLE pairing events
• Push BLE config via mobile app
• Real-world vehicle deployments
• Publishing full Medium article + case study

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Let me know what you're building — and if you're working on embedded systems or sustainable tech, let's connect!

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Tags: #esp32 #c++ #iot #ble #embedded #platformio