Added device registration doc and functional description to station_example_main.c

duckdns/station/docs/device_registration.md

@@ -0,0 +1,35 @@
+# Device Registration and SAS Token Generation for Azure IoT Hub
+
+## 🔧 Prerequisites
+
+- Azure Subscription
+- Azure IoT Hub created
+- Azure CLI installed
+- Device created in IoT Hub
+
+---
+
+## 1️⃣ Register a Device
+
+```bash
+az login
+az account set --subscription "<your-subscription-id>"
+
+az iot hub device-identity create --hub-name <your-hub-name> --device-id <your-device-id>
+
+2️⃣ Get Device Connection String
+az iot hub device-identity show-connection-string --hub-name <your-hub-name> --device-id <your-device-id>
+
+3️⃣ Generate SAS Token
+
+import base64, hmac, hashlib, time, urllib.parse
+
+def generate_sas_token(uri, key, expiry=3600):
+    ttl = int(time.time()) + expiry
+    sign_key = f"{urllib.parse.quote_plus(uri)}\n{ttl}"
+    signature = base64.b64encode(hmac.new(base64.b64decode(key), sign_key.encode(), hashlib.sha256).digest())
+    return f"SharedAccessSignature sr={uri}&sig={urllib.parse.quote_plus(signature.decode())}&se={ttl}"
+
+4️⃣ Use SAS Token in Firmware
+Set the Authorization header in MQTT/TLS to the token string.
+

duckdns/station/main/station_example_main.c

@@ -1,3 +1,20 @@
+/*
+ * station_example_main.c
+ *
+ * Description:
+ *   This ESP32 app sets a static IP, updates a DuckDNS record,
+ *   and sends messages to Azure IoT Hub using SAS authentication.
+ *
+ * Functional Overview:
+ *   - Connects to Wi-Fi using static IP
+ *   - Sends updates to DuckDNS periodically
+ *   - Connects to Azure IoT Hub via MQTT over TLS
+ *   - Uses SAS tokens for secure device authentication
+ *
+ * Author: Advait Achanta
+ */
+
+
 #include <stdio.h>
 #include <string.h>
 #include "esp_wifi.h"