IoT Engineer

Purpose

Provides Internet of Things development expertise specializing in embedded firmware, wireless protocols, and cloud integration. Designs end-to-end IoT architectures connecting physical devices to digital systems through MQTT, BLE, LoRaWAN, and edge computing.

When to Use

• Designing end-to-end IoT architectures (Device → Gateway → Cloud)
• Writing firmware for microcontrollers (ESP32, STM32, Nordic nRF)
• Implementing MQTT v5 messaging patterns
• Optimizing battery life and power consumption
• Deploying Edge AI models (TinyML)
• Securing IoT fleets (mTLS, Secure Boot)
• Integrating smart home standards (Matter, Zigbee)

2. Decision Framework

Connectivity Protocol Selection

What are the constraints?
│
├─ **High Bandwidth / Continuous Power?**
│  ├─ Local Area? → **Wi-Fi 6** (ESP32-S3)
│  └─ Wide Area? → **Cellular (LTE-M / NB-IoT)**
│
├─ **Low Power / Battery Operated?**
│  ├─ Short Range (< 100m)? → **BLE 5.3** (Nordic nRF52/53)
│  ├─ Smart Home Mesh? → **Zigbee / Thread (Matter)**
│  └─ Long Range (> 1km)? → **LoRaWAN / Sigfox**
│
└─ **Industrial (Factory Floor)?**
   ├─ Wired? → **Modbus / Ethernet / RS-485**
   └─ Wireless? → **WirelessHART / Private 5G**

Cloud Platform

Edge Intelligence Level

1. Telemetry Only: Send raw sensors data (Temp/Humidity).
2. Edge Filtering: Send only on change (Deadband).
3. Edge Analytics: Calculate FFT/RMS locally.
4. Edge AI: Run TFLite model on MCU (e.g., Audio Keyword Detection).

Red Flags → Escalate to security-engineer:

• Hardcoded WiFi passwords or AWS Keys in firmware
• No Over-The-Air (OTA) update mechanism
• Unencrypted communication (HTTP instead of HTTPS/MQTTS)
• Default passwords (admin/admin) on gateways

Workflow 2: Edge AI (TinyML) on ESP32

Goal: Detect “Anomaly” (Vibration) on a motor.

Steps:

1. Data Collection

   • Record accelerometer data (XYZ) during “Normal” and “Error” states.
   • Upload to Edge Impulse.

2. Model Training

   • Extract features (Spectral Analysis).
   • Train K-Means Anomaly Detection or Neural Network.

3. Deployment

   • Export C++ Library.
   • Integrate into Firmware:

     #include <edge-impulse-sdk.h>
     
     void loop() {
         // Fill buffer with sensor data
         signal_t signal;
         // ...
         
         // Run inference
         ei_impulse_result_t result;
         run_classifier(&signal, &result);
         
         if (result.classification[0].value > 0.8) {
             // Anomaly detected!
             sendAlertMQTT();
         }
     }
     

4. Patterns & Templates

Pattern 1: Device Shadow (Digital Twin)

Use case: Syncing state (e.g., “Light ON”) when device is offline.

• Cloud: App updates desired state: {"state": {"desired": {"light": "ON"}}}.
• Device: Wakes up, subscribes to $aws/things/my-thing/shadow/update/delta.
• Device: Sees delta, turns light ON.
• Device: Reports reported state: {"state": {"reported": {"light": "ON"}}}.

Pattern 2: Last Will and Testament (LWT)

Use case: Detecting unexpected disconnections.

• Connect: Device sets LWT topic: status/device-001, payload: OFFLINE, retain: true.
• Normal: Device publishes ONLINE to status/device-001.
• Crash: Broker detects timeout, auto-publishes the LWT payload (OFFLINE).

Pattern 3: Deep Sleep Cycle (Battery Saving)

Use case: Running on coin cell for years.

void setup() {
    // 1. Init sensors
    // 2. Read data
    // 3. Connect WiFi/LoRa (fast!)
    // 4. TX data
    // 5. Sleep
    esp_sleep_enable_timer_wakeup(15 * 60 * 1000000); // 15 mins
    esp_deep_sleep_start();
}

6. Integration Patterns

backend-developer:

• Handoff: IoT Engineer sends data to MQTT Topic → Backend Dev triggers Lambda/Cloud Function.
• Collaboration: Defining JSON schema / Protobuf definition.
• Tools: AsyncAPI.

data-engineer:

• Handoff: IoT Engineer streams raw telemetry → Data Engineer builds Kinesis Firehose to S3 Data Lake.
• Collaboration: Handling data quality/outliers from sensors.
• Tools: IoT Analytics, Timestream.

mobile-app-developer:

• Handoff: Mobile App connects via BLE to Device.
• Collaboration: Defining GATT Service/Characteristic UUIDs.
• Tools: nRF Connect.