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Azure: IoT Dashboard for ESP32 Telemetry

23 Sep 2024

  1. Services covered
  2. Lab description
  3. Prerequisites
  4. Lab steps
  5. Lab files
  6. Troubleshooting
  7. Acknowledgements

Services covered

  • Azure IoT Hub (free tier)
  • Azure IoT Central (free tier)

Lab description

This lab demonstrates how to collect built-in telemetry from an ESP32 microcontroller and visualize it using a real-time dashboard in Azure IoT Central. Telemetry data includes:

  • Wi-Fi signal strength
  • Free heap memory
  • CPU temperature
  • Uptime

The ESP32 will send telemetry to Azure IoT Hub, and Azure IoT Central will be used to build a graphical dashboard for real-time monitoring and analysis.

Prerequisites

  1. Hardware:

  2. ESP32 microcontroller

  3. Software:

  4. Arduino IDE with ESP32 board support

  5. Azure IoT SDK (AzureIoTHub library)

  6. Azure Setup:

  7. Azure account with access to Azure IoT Hub and Azure IoT Central.

Lab steps

1. Create an Azure IoT Hub

  1. Go to the Azure portal.
  2. Click Create a resource, search for IoT Hub, and click Create.
  3. Choose Free Tier to avoid costs.
  4. Create a resource group (e.g. ESP32-Telemetry-RG) and give the IoT Hub a name (e.g., ESP32Hub).
  5. Networking: Public Access is fine. Communication is encrypted (TLS) and authenticated (SAS tokens) and works on Free Tier.

  6. Management: Shared Access Policies + RBAC

    • The ESP32 uses Shared Access Policies (with a SAS token).
    • You'll use RBAC to access the IoT Hub through the portal.
    • The monitoring app can be use RBAC to read telemetry to display it on a dashboard.

  7. After creation, go to IoT Hub > IoT Devices and click + New to register a new device.

  8. Save the device connection string; you’ll use this in the ESP32 code.

2. Code the ESP32 for Sending Telemetry

  1. Install the required libraries in Arduino IDE:
  2. Azure IoT SDK for ESP32 (AzureIoTHub via Library Manager).

  3. WiFi Library (built-in).

  4. Use the following code to send Wi-Fi signal strength, free heap memory, CPU temperature, and uptime to Azure IoT Hub:

#include <WiFi.h>
#include <Esp32MQTTClient.h>

const char* ssid = "your-SSID";
const char* password = "your-PASSWORD";
const char* connectionString = "HostName=your-iot-hub.azure-devices.net;DeviceId=your-device-id;SharedAccessKey=your-device-key";

static const char* telemetryMessageTemplate = "{\"wifiSignalStrength\":%d,\"freeHeapMemory\":%d,\"cpuTemperature\":%d,\"uptime\":%d}";

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
  }
  Esp32MQTTClient_Init((const uint8_t*)connectionString, true);
}

void loop() {
  int wifiSignalStrength = WiFi.RSSI();
  int freeHeapMemory = ESP.getFreeHeap();
  int cpuTemperature = (esp_random() % 20) + 50;
  int uptime = millis() / 1000;

  char telemetryMessage[256];
  sprintf(telemetryMessage, telemetryMessageTemplate, wifiSignalStrength, freeHeapMemory, cpuTemperature, uptime);

  if (Esp32MQTTClient_SendEvent(telemetryMessage)) {
    Serial.println("Telemetry sent:");
    Serial.println(telemetryMessage);
  } else {
    Serial.println("Telemetry failed.");
  }

  delay(5000);
}
  1. Upload the code to your ESP32 and monitor the serial console to ensure it's sending telemetry.

3. Set Up Azure IoT Central

  1. Go to Azure IoT Central and create a new application using the Free Tier.
  2. Under Device Templates, create a new template for your ESP32 (e.g., ESP32-Template).
  3. Define telemetry fields (wifiSignalStrength, freeHeapMemory, cpuTemperature, uptime), set their types to Number, and save.

4. Connect Your ESP32 Device to IoT Central

  1. Under Devices, create a new device based on the ESP32-Template and copy the Device Connection String.
  2. Update the ESP32 connection string in the code if necessary and re-upload the code to the ESP32.
  3. Verify that the device connects and sends telemetry data by checking the Telemetry tab for your device in IoT Central.

5. Create a Dashboard in IoT Central

  1. Navigate to Dashboards and create a new dashboard.
  2. Add the following widgets:
  3. Line Chart for wifiSignalStrength and cpuTemperature.
  4. Gauge for freeHeapMemory.
  5. Number Widget for uptime.
  6. Save your dashboard and monitor real-time data from the ESP32.

Lab files

Troubleshooting

  • Connection Issues: Ensure that your Wi-Fi credentials are correct and the ESP32 is within range.
  • Azure IoT Hub Configuration: Verify that the device connection string matches the one from Azure IoT Hub or IoT Central.
  • Telemetry Not Appearing: Check the serial monitor for errors. If telemetry isn’t sent, check the IoT Central Device page for any communication issues.

Acknowledgements