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Connecting an ESP32 device to Azure IoT using the Azure SDK for Embedded C
c
azure-iot
azure-iot-pnp
azure-iot-dps
azure-iot-hub

How to Setup and Run Azure SDK for Embedded C ADU on Espressif ESP32

Before you proceed

This sample is based on the Azure IoT SDK for C, uses a bare metal (no RTOS) approach and has support for Arduino IDE.

There is a different sample for the ESP32 with the Azure IoT middleware for FreeRTOS (requires FreeRTOS to work).

If this is what you’re looking for please visit this GitHub repo.

Introduction

This is a "to-the-point" guide outlining how to run an Azure SDK for Embedded C ADU sample on an ESP32 microcontroller. The command line examples are tailored to Debian/Ubuntu environments.

What is Covered

  • Configuration instructions for the Arduino IDE to compile a sample using the Azure SDK for Embedded C.
  • Setting up and configuring the necessary services for the scenario.
  • Configuration, build, and run instructions for the IoT ADU sample.

The following was run on Windows 11, with Arduino IDE 2.1.0 and ESP32 board library version 2.0.9.

Prerequisites

  • Have an Azure account created.

  • Have an Azure IoT Hub created.

    Important: To use Azure Device Update you must have an Azure IoT Hub with scale unit S1, S2, S3. This sample will not work with a Azure IoT Hub 'Basic' scale unit or free tier.

  • Have an Azure Device Update instance created and linked to your Azure IoT Hub.

  • Have a logical device created in your Azure IoT Hub: using authentication type "Symmetric Key" or "X.509 self-signed".

    • Symmetric Key: follow this guidance to create a device.In this case, the device keys are used to automatically generate a SAS token for authentication.
    • X.509 self-signed cert: Instructions on how to create an X.509 cert for tests can be found here (Step 1). Please note that you might need to install some of the prerequisites like OpenSSL.

  • Have the latest Arduino IDE installed.

  • Have the ESP32 board support installed on Arduino IDE.

    • ESP32 boards are not natively supported by Arduino IDE, so you need to add them manually.
    • Follow the instructions in the official ESP32 repository.
    • If your ESP32 board is not recognized and a COM port is not mapped by your computer, try installing the serial port drivers recommended by ESPRESSIF.

  • Install Azure CLI and Azure IoT Module

    See steps to install both here.

Add Azure IoT Hub Device to an ADU Deployment Group

Add the "ADUGroup" tag to the device's top-level twin document. This is used to group devices together, and you may choose whichever tag you prefer (e.g., "embeddedSDK").

"tags": {
    "ADUGroup": "<your-tag-here>"
},

Viewing the device twin on the portal, the "tag" section should look similar to the following. Don't worry if you do or do not have a "deviceUpdate" section in the "ADUGroup" tag. ADU adds that as a default group.

img

Device Setup Instructions

  1. Run the Arduino IDE.

  2. Install the Azure SDK for Embedded C library.

    • On the Arduino IDE, go to menu Sketch, Include Library, Manage Libraries....
    • Search for and install azure-sdk-for-c.
    • Make sure to install version 1.1.0 or later to use the new Azure Device Update client of the Embedded C SDK.

  3. Open the ESPRESSIF ESP32 sample.

    • On the Arduino IDE, go to menu File, Examples, azure-sdk-for-c.
    • Click on Azure_IoT_Adu_ESP32 to open the sample.

  4. Configure the ESPRESSIF ESP32 sample.

    Enter your Azure IoT Hub and device information into the sample's iot_configs.h:

    • Add your Wi-Fi SSID to IOT_CONFIG_WIFI_SSID
    • Add your Wi-Fi password to IOT_CONFIG_WIFI_PASSWORD
    • Add you IoTHub Name to IOT_CONFIG_IOTHUB_FQDN
    • Add your Device ID to IOT_CONFIG_DEVICE_ID
    • If using X.509 Cert:
      • Uncomment the #define IOT_CONFIG_USE_X509_CERT
      • Add your cert to IOT_CONFIG_USE_X509_CERT
      • Add your cert PK to IOT_CONFIG_DEVICE_CERT_PRIVATE_KEY
    • If using Symmetric Key:
      • Add your device key to IOT_CONFIG_DEVICE_KEY

  5. Connect the ESP32 microcontroller to your USB port.

    After connecting the device,

    • Go to menu Tools, Board and select ESP32.
    • Go to menu Tools, Port and select the port to which the microcontroller is connected.

  6. Select the appropriate partition scheme for your device. Go to Tools -> Partition Scheme -> Minimal SPIFFS.

  7. Upload the sketch.

    • Go to menu Sketch and click on Upload.

      Expected output of the upload: 

      Executable segment sizes:
IROM   : 361788          - code in flash         (default or ICACHE_FLASH_ATTR)
IRAM   : 26972   / 32768 - code in IRAM          (ICACHE_RAM_ATTR, ISRs...)
DATA   : 1360  )         - initialized variables (global, static) in RAM/HEAP
RODATA : 2152  ) / 81920 - constants             (global, static) in RAM/HEAP
BSS    : 26528 )         - zeroed variables      (global, static) in RAM/HEAP
Sketch uses 392272 bytes (37%) of program storage space. Maximum is 1044464 bytes.
Global variables use 30040 bytes (36%) of dynamic memory, leaving 51880 bytes for local variables. Maximum is 81920 bytes.
/home/user/.arduino15/packages/esp8266/tools/python3/3.7.2-post1/python3 /home/user/.arduino15/packages/esp8266/hardware/esp8266/2.7.1/tools/upload.py --chip esp8266 --port /dev/ttyUSB0 --baud 230400 --before default_reset --after hard_reset write_flash 0x0 /tmp/arduino_build_826987/azure_iot_hub_telemetry.ino.bin
esptool.py v2.8
Serial port /dev/ttyUSB0
Connecting....
Chip is ESP8266EX
Features: WiFi
Crystal is 26MHz
MAC: dc:4f:22:5e:a7:09
Uploading stub...
Running stub...
Stub running...
Changing baud rate to 230400
Changed.
Configuring flash size...
Auto-detected Flash size: 4MB
Compressed 396432 bytes to 292339...

Writing at 0x00000000... (5 %)
Writing at 0x00004000... (11 %)
Writing at 0x00008000... (16 %)
Writing at 0x0000c000... (22 %)
Writing at 0x00010000... (27 %)
Writing at 0x00014000... (33 %)
Writing at 0x00018000... (38 %)
Writing at 0x0001c000... (44 %)
Writing at 0x00020000... (50 %)
Writing at 0x00024000... (55 %)
Writing at 0x00028000... (61 %)
Writing at 0x0002c000... (66 %)
Writing at 0x00030000... (72 %)
Writing at 0x00034000... (77 %)
Writing at 0x00038000... (83 %)
Writing at 0x0003c000... (88 %)
Writing at 0x00040000... (94 %)
Writing at 0x00044000... (100 %)
Wrote 396432 bytes (292339 compressed) at 0x00000000 in 13.0 seconds (effective 243.4 kbit/s)...
Hash of data verified.

Leaving...
Hard resetting via RTS pin...

  8. Monitor the MCU (microcontroller) locally via the Serial Port.

    • Go to menu Tools, Serial Monitor.

      If you perform this step right away after uploading the sketch, the serial monitor will show an output similar to the following upon success:

      1970/1/1 00:00:41 [INFO] WiFi connected, IP address: 192.168.1.123
1970/1/1 00:00:41 [INFO] Setting time using SNTP
....
2022/11/2 20:56:20 [INFO] Time initialized!
2022/11/2 20:56:20 [INFO] ------------------------------------------------------------------------------
2022/11/2 20:56:20 [INFO] ADU SAMPLE
2022/11/2 20:56:20 [INFO] Version: 1.0
2022/11/2 20:56:20 [INFO] ------------------------------------------------------------------------------
2022/11/2 20:56:20 [INFO] Client ID: mydeviceid
2022/11/2 20:56:20 [INFO] Username: myiothub.azure-devices.net/mydeviceid/?api-version=2020-09-30&DeviceClientType=c%2f1.4.0-beta.1(ard;esp32)&model-id=dtmi%3Aazure%3Aiot%3AdeviceUpdateModel%3B1
2022/11/2 20:202256/11/2: 20:56:2020 [INFO]  [INFO] MQTT event MQTT_EVENT_BEFORE_CONNECT
MQTT client started
2022/11/2 20:56:20 [INFO] Requesting all device properties
2022/11/2 20:56:20 [INFO] Client requesting device property document from service.
2022/11/2 20:56:27 [INFO] MQTT event MQTT_EVENT_CONNECTED

New Image Instructions

In order to update our device, we have to build the image which our device will update to. We will have to direct the Arduino IDE to specify an output directory so that we can easily find the binary. Open the preferences.txt (find its path going to menu File, Preferences) and add build.path=C:\Arduino-output (or whichever directory you prefer), then restart the Arduino IDE.

Once you are done with the ADU sample, you may remove the added configuration to restore the build output to its original location.

  1. Update the image version in the sketch configuration

    • In iot_configs.h, change the ADU_DEVICE_VERSION to version 1.1.

  2. Click on "Verify" to build the update image.

    Once the build is complete, you should then have a file called Azure_IoT_Adu_ESP32.ino.bin in your output directory. Copy that file to a new directory C:\ADU-update, and rename it Azure_IoT_Adu_ESP32_1.1.bin

Generate the ADU Update Manifest

Open PowerShell.

Navigate to the C:\ADU-update directory.

Run the following command:

az iot du update init v5 --update-provider Contoso --update-name ESP32-Embedded --update-version 1.1 --compat deviceModel=ESP32-Embedded deviceManufacturer=ESPRESSIF --step handler=microsoft/swupdate:1 properties='{\"installedCriteria\":\"1.1\"}' --file path=./Azure_IoT_Adu_ESP32_1.1.bin > ./Contoso.ESP32-Embedded.1.1.importmanifest.json

Verify you have the following files in your ADU-update directory:

  • Azure_IoT_Adu_ESP32_1.1.bin
  • Contoso.ESP32-Embedded.1.1.importmanifest.json

Import the Update Manifest

To import the update (Azure_IoT_Adu_ESP32_1.1.bin) and manifest (Contoso.ESP32-Embedded.1.1.importmanifest.json), follow the instructions at the link below:

Deploy Update

To deploy the update to your ESP32, follow the link below:

Monitor the Update Process

In Arduino IDE, go to menu Tools, Serial Monitor.

Once the update request is received by the device, a log similar to this should be displayed:

2022/11/3 05:25:32 [INFO] Client received a properties topic.
2022/11/3 05:25:32 [INFO] Status: 200
2022/11/3 05:25:32 [INFO] Message Type: Desired Properties
2022/11/3 05:25:32 [INFO] Parsed Azure device update manifest.
2022/11/3 05:25:32 [INFO] [JWS] Calculated manifest SHA matches parsed SHA
2022/11/3 05:25:32 [INFO] Manifest authenticated successfully
2022/11/3 05:25:32 [INFO] Sending manifest property accept
...

And once the update is complete (including the device automatic reboot), the new version should be printed:

2022/11/3 05:26:22 [INFO] ------------------------------------------------------------------------------
2022/11/3 05:26:22 [INFO] ADU SAMPLE
2022/11/3 05:26:22 [INFO] Version: 1.1
2022/11/3 05:26:22 [INFO] ------------------------------------------------------------------------------

Certificates - Important to know

The Azure IoT service certificates presented during TLS negotiation shall be always validated, on the device, using the appropriate trusted root CA certificate(s).

The Azure SDK for C Arduino library automatically installs the root certificate used in the United States regions, and adds it to the Arduino sketch project when the library is included.

For other regions (and private cloud environments), please use the appropriate root CA certificate.

Additional Information

For important information and additional guidance about certificates, please refer to this blog post from the security team.

Troubleshooting

  • The error policy for the Embedded C SDK client library is documented here.
  • File an issue via Github Issues.
  • Check previous questions or ask new ones on StackOverflow using the azure and c tags.

Contributing

This project welcomes contributions and suggestions. Find more contributing details here.

License

Azure SDK for Embedded C is licensed under the MIT license.