Compiling problem when connecting ESP32 to Azure Iot Central.

Question

Refer to "Connect ESP32 to Azure IoT Central" topic in https://learn.microsoft.com/en-us/answers/questions/1627220/connect-esp32-to-azure-iot-central , I followed the guidance, specifically adjusting the Azure IoT_PnP_Template.cpp file. As a result, I successfully compiled the code, and the outcome meets expectations.

Moving forward, I am interested in enhancing the functionality of Azure IoT_PnP_Template.cpp by enabling the transmission of parameters from the void loop(). This adjustment would greatly enhance usability. Below, I've outlined the changes I made to Azure IoT_PnP_Template.cpp and Azure_IoT_Central_ESP32.ino for your review:

Azure _IoT_PnP__Template.cpp (Please see 'double x2', 'double x3' and 'temperature' in Azure _IoT_PnP__Template.cpp)

static int generate_telemetry_payload(
  uint8_t* payload_buffer, size_t payload_buffer_size, size_t* payload_buffer_length, double x2);
static int generate_telemetry_payload(uint8_t* payload_buffer, size_t payload_buffer_size, size_t* payload_buffer_length, double x2)
{
  az_json_writer jw;
  az_result rc;
  az_span payload_buffer_span = az_span_create(payload_buffer, payload_buffer_size);
  az_span json_span;
  float temperature, humidity, uvIndex;
  int32_t visibleLight, infraredLight;
  // Acquiring data from sensors.
  temperature = x2;
  humidity = 30;
  
  uvIndex = 200;
  // The index is multiplied by 100 so to get the
  // integer index, divide by 100!
  uvIndex /= 100.0;  
  
  visibleLight = 31;
  infraredLight = 32;
  rc = az_json_writer_init(&jw, payload_buffer_span, NULL);
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed initializing json writer for telemetry.");
  rc = az_json_writer_append_begin_object(&jw);
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed setting telemetry json root.");
  rc = az_json_writer_append_property_name(&jw, AZ_SPAN_FROM_STR(TELEMETRY_PROP_NAME_TEMPERATURE));
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed adding temperature property name to telemetry payload.");
  rc = az_json_writer_append_double(&jw, temperature, DOUBLE_DECIMAL_PLACE_DIGITS);
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed adding temperature property value to telemetry payload. ");
  rc = az_json_writer_append_property_name(&jw, AZ_SPAN_FROM_STR(TELEMETRY_PROP_NAME_HUMIDITY));
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed adding humidity property name to telemetry payload.");
  rc = az_json_writer_append_double(&jw, humidity, DOUBLE_DECIMAL_PLACE_DIGITS);
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed adding humidity property value to telemetry payload. ");
  rc = az_json_writer_append_property_name(&jw, AZ_SPAN_FROM_STR(TELEMETRY_PROP_NAME_UV_INDEX));
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed adding uv index property name to telemetry payload.");
  rc = az_json_writer_append_double(&jw, uvIndex, DOUBLE_DECIMAL_PLACE_DIGITS);
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed adding uv index property value to telemetry payload.");
  rc = az_json_writer_append_property_name(&jw, AZ_SPAN_FROM_STR(TELEMETRY_PROP_NAME_VISIBLE_LIGHT));
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed adding visible light property name to telemetry payload.");
  rc = az_json_writer_append_int32(&jw, visibleLight);
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed adding visible light property value to telemetry payload.");
  rc = az_json_writer_append_property_name(&jw, AZ_SPAN_FROM_STR(TELEMETRY_PROP_NAME_INFRARED_LIGHT));
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed adding infrared light property name to telemetry payload.");
  rc = az_json_writer_append_int32(&jw, infraredLight);
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed adding infrared light property value to telemetry payload.");
  rc = az_json_writer_append_end_object(&jw);
  EXIT_IF_AZ_FAILED(rc, RESULT_ERROR, "Failed closing telemetry json payload.");
  payload_buffer_span = az_json_writer_get_bytes_used_in_destination(&jw);
  if ((payload_buffer_size - az_span_size(payload_buffer_span)) < 1)
  {
    LogError("Insufficient space for telemetry payload null terminator.");
    return RESULT_ERROR;
  }
  payload_buffer[az_span_size(payload_buffer_span)] = null_terminator;
  *payload_buffer_length = az_span_size(payload_buffer_span);
 
  return RESULT_OK;
}
int azure_pnp_send_telemetry(azure_iot_t* azure_iot, double x3)
{
  _az_PRECONDITION_NOT_NULL(azure_iot);
  time_t now = time(NULL);
  if (now == INDEFINITE_TIME)
  {
    LogError("Failed getting current time for controlling telemetry.");
    return RESULT_ERROR;
  }
  else if (last_telemetry_send_time == INDEFINITE_TIME ||
           difftime(now, last_telemetry_send_time) >= telemetry_frequency_in_seconds)
  {
    size_t payload_size;
    last_telemetry_send_time = now;
    if (generate_telemetry_payload(data_buffer, DATA_BUFFER_SIZE, &payload_size, x3) != RESULT_OK)
    {
      LogError("Failed generating telemetry payload.");
      return RESULT_ERROR;
    }
    if (azure_iot_send_telemetry(azure_iot, az_span_create(data_buffer, payload_size)) != 0)
    {
      LogError("Failed sending telemetry.");
      return RESULT_ERROR;
    }
  }
  return RESULT_OK;
}

Azure_IoT_Central_ESP32.ino (Please see '42' in Azure_IoT_Central_ESP32.ino)

void loop()
{
  
  if (WiFi.status() != WL_CONNECTED)
  {
    azure_iot_stop(&azure_iot);
    connect_to_wifi();
  }
  else
  {
    switch(azure_iot_get_status(&azure_iot))
    {
      case azure_iot_connected:
        if (send_device_info)
        {
          (void)azure_pnp_send_device_info(&azure_iot, properties_request_id++);
           send_device_info = false; // Only need to send once.
        }
        else if (azure_pnp_send_telemetry(&azure_iot, 42) != 0)
        {
          LogError("Failed sending telemetry.");          
        }
        break;
      case azure_iot_error:
        LogError("Azure IoT client is in error state." );
        azure_iot_stop(&azure_iot);
        break;
      case azure_iot_disconnected:
        azure_iot_start(&azure_iot);
        break;
      default:
        break;
    }
    azure_iot_do_work(&azure_iot);
  }
}

After compiling, I encountered an error message stating "too many arguments to function 'int azure_pnp_send_telemetry(azure_iot_t*)". Despite my efforts to resolve this issue, I have been unable to find a solution. I'm still developing my coding skills. I would greatly appreciate your help and support. Thank you for assistance.

Answer 1

Hi @Abball Thank you for posting the question here.

The code linking is relied based on the included header file references. In this case, the compiler executes Azure_IoT_Central_ESP32.ino as the main program and looks for reference functions based on the definitions included in the header files. For this specific azure_pnp_send_telemetry function, the definition for reference has been defined in the line 70 of file. This lets the complier look for a function with the appropriate arguments.

Please make sure to modify the method signature in the following code Azure_IoT_PnP_Template.h too to resolve this error.

Hope this helps! Please let us know if you still encounter any issues.

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