ESP32 IoT Azure

ESP32 library to access Azure IoT Services, using the Azure IoT Middleware for FreeRTOS interface, in an easier and cleaner way.
Just clone, configure using menuconfig and connect!

Characteristics

• ESP-IDF: v5.1
• Written in C using:
  • ESP-IDF Framework
  • Azure IoT Middleware for FreeRTOS
  • Azure SDK for Embedded C
• APIs:
  • All functions from Azure IoT Middleware for FreeRTOS
  • Custom extensions
• Features supported (IoT Hub/IoT Central):
  • Device Provisioning Service (DPS)
  • Device Update
  • Digital Twins
  • IoT Plug and Play
• Transport:
  • Socket: esp_tls with built-in connection retries and updated Azure certificates.
  • HTTP: FreeRTOS coreHTTP
  • MQTT: FreeRTOS coreMQTT
• Cryptography: mbedtls
• Configurable: using menuconfig

Documentation

• Everything is at the docs folder.
• Examples:
  • Azure IoT Hub: examples/iot_hub
  • Azure Device Provisioning Service: examples/provisioning
  • Azure Device Update: examples/adu

Code Size

Build options:

• Compile optimized for size (CONFIG_COMPILER_OPTIMIZATION_SIZE=y).
• Error logging (CONFIG_LOG_DEFAULT_LEVEL_ERROR=y).
• Azure Cloud RSA certificate: (CONFIG_ESP32_IOT_AZURE_HUB_CERT_USE_AZURE_RSA=y)

This chart already includes the Azure IoT certificate and Device Update root key sizes.

	DRAM (bss,data)	Flash (code,rodata)
IoT Hub + PnP + DPS + ADU + ADU workflow	874 B	97.41 KB
IoT Hub + PnP + DPS	12 B	54.73 KB
IoT Hub + PnP	12 B	44.37 KB

Example: Getting Device and Hub Info from DPS

#include "esp32_iot_azure/azure_iot_sdk.h"
#include "esp32_iot_azure/azure_iot_provisioning.h"
#include "esp32_iot_azure/extension/azure_iot_provisioning_extension.h"

void app_main(void)
{
    // 1. Configure this library via menuconfig.
    // 2. Connect to WiFi.
    // 3. Set up SNTP.

    buffer_t symmetric_key = BUFFER_FROM_LITERAL("you_device_enrollment_symmetric_key");
    buffer_t registration_id = BUFFER_FROM_LITERAL("your_device_registration_id");

    buffer_t registration_payload = BUFFER_FOR_DPS_PNP_REGISTRATION_PAYLOAD();
    buffer_t hostname = BUFFER_WITH_FIXED_LENGTH(AZURE_CONST_HOSTNAME_MAX_LENGTH);
    buffer_t device_id = BUFFER_WITH_FIXED_LENGTH(AZURE_CONST_DEVICE_ID_MAX_LENGTH);

    azure_iot_sdk_init();

    AzureIoTProvisioningClientOptions_t *dps_client_options = NULL;
    buffer_t buffer = {
        .length = 2048,
        .buffer = (uint8_t *)malloc(2048)};

    azure_dps_context_t *dps = azure_dps_create(&buffer);
    azure_dps_options_init(dps, &dps_client_options);
    azure_dps_init_default(dps, registration_id->buffer, registration_id->length);
    azure_dps_auth_set_symmetric_key(dps, symmetric_key->buffer, symmetric_key->length);
    azure_dps_create_pnp_registration_payload(registration_payload.buffer, &registration_payload.length);
    azure_dps_set_registration_payload(dps, registration_payload.buffer, registration_payload.length);
    azure_dps_register(dps);
    azure_dps_get_device_and_hub(dps,
                                 hostname->buffer,
                                 &hostname->length,
                                 device_id->buffer,
                                 &device_id->length);
    azure_dps_deinit(dps);
    azure_dps_free(dps);

    free(buffer.buffer);

    azure_iot_sdk_deinit();

    ESP_LOGI(TAG, "hostname: %.*s", (int)hostname.length, (char *)hostname.buffer);
    ESP_LOGI(TAG, "device_id: %.*s", (int)device_id.length, (char *)device_id.buffer);
}