ESP32 Forum

Posted: **Fri Jul 07, 2023 6:50 pm**

Hello Everyone,
I am new to ESP32 and wanted to write a simple application to get weather information from the OpenWeatherMap website.
It works fine for the first time, but when I try to request the data next time, my program crashes and restarts with the following message.

Code: [Select all] [Expand/Collapse]

Guru Meditation Error: Core  0 panic'ed (LoadProhibited). Exception was unhandled.

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The following is the piece of the code for reference, and it is crashing when "openweathermap_send_request" is called second time, and more specifically while calling the function "esp_err_t err = esp_http_client_perform(client);"

Code: [Select all] [Expand/Collapse]

// OpenWeatherMap Task
static void openweathermap_task(void *pvParameters)
{
  // Initialize the City Names
  strcpy(city_weather[0].city_name, "manali");
  strcpy(city_weather[1].city_name, "kashmir");
  strcpy(city_weather[2].city_name, "jaipur");
  strcpy(city_weather[3].city_name, "delhi");
  
  for( ; ; )
  {
    openweathermap_send_request();
    vTaskDelay(HTTP_REQ_EXEC_RATE / portTICK_PERIOD_MS);
  }
 
  vTaskDelete(NULL);
}
 
static void openweathermap_send_request(void)
{
  char openweathermap_url[200];
  city_weather_index = 0;  // added for debugging
  snprintf( openweathermap_url, sizeof(openweathermap_url), \
            "%s%s%s", CLIENT_REQ_PRE, city_weather[city_weather_index].city_name, CLIENT_REQ_POST);
 
  esp_http_client_config_t config =
  {
    .url = openweathermap_url,
    .method = HTTP_METHOD_GET,
    .event_handler = openweathermap_event_handler,
  };
 
  ESP_LOGI(TAG, "OpenWeatherMap Task Execution Started");
 
  esp_http_client_handle_t client = esp_http_client_init(&config);
  esp_http_client_set_header(client, CLIENT_KEY, CLIENT_VALUE);
  esp_err_t err = esp_http_client_perform(client);
  if( err == ESP_OK )
  {
    int status = esp_http_client_get_status_code(client);
    if(status == 200)
    {
      ESP_LOGI(TAG, "City=%s, Message Sent Successfully", city_weather[city_weather_index].city_name);
      city_weather_index++;
      // Reset back to Initial Position
      if( city_weather_index >= NUM_OF_CITIES )
      {
        city_weather_index = 0;
      }
    }
    else
    {
      ESP_LOGI(TAG, "City=%s, Message Sent Failed", city_weather[city_weather_index].city_name);
    }
  }
  else
  {
    ESP_LOGI(TAG, "City=%s, Message Sent Failed", city_weather[city_weather_index].city_name);
  }
  esp_http_client_cleanup(client);
  ESP_LOGI(TAG, "OpenWeatherMap Task Execution Complete");
}
 
static esp_err_t openweathermap_event_handler(esp_http_client_event_t *event)
{
  switch(event->event_id)
  {
    case HTTP_EVENT_ON_DATA:
      // Resize the Buffer to fit the new chunk of the data
      response_data = realloc(response_data, response_len + event->data_len);
      // Copy the Data
      memcpy(response_data+response_len, event->data, event->data_len);
      // Update the Length
      response_len += event->data_len;
      // Only used for debugging
      // ESP_LOGI("OpenWeatherAPI", "Partial Received Data: %d", event->data_len);
      break;
    case HTTP_EVENT_ON_FINISH:
      all_data_received = true;
      // NOTE: TAG is different here (debugging purpose)
      // ESP_LOGI("OpenWeatherAPI", "Received Data: %s", response_data);
      // Decode/Parse the weather data from the response data
      openweathermap_get_weather(response_data, &city_weather[0]);
      // free up the space, and reset the response length
      free(response_data);
      response_len = 0;
      ESP_LOGI("OpenWeatherAPI", "City=%s, Temp=%f, Pressure=%d, Humidity=%d", \
                city_weather[city_weather_index].city_name,   \
                city_weather[city_weather_index].temperature, \
                city_weather[city_weather_index].pressure,    \
                city_weather[city_weather_index].humidity);
      ESP_LOGI("OpenWeatherAPI", "Exiting Event Handler");
      break;
    default:
      break;
  }
  return ESP_OK;
}

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Logs on Terminal when code crashed.

Code: [Select all] [Expand/Collapse]

I (27940) WIFI: OpenWeatherMap Task Execution Complete
I (30920) WIFI: Hello World from Main Task
I (32940) WIFI: OpenWeatherMap Task Execution Started
I (35920) WIFI: Hello World from Main Task
I (35970) OpenWeatherAPI: City=manali, Temp=30.040001, Pressure=1007, Humidity=82
I (35970) OpenWeatherAPI: Exiting Event Handler
I (35970) WIFI: City=manali, Message Sent Successfully
I (35980) WIFI: OpenWeatherMap Task Execution Complete
I (40920) WIFI: Hello World from Main Task
I (40980) WIFI: OpenWeatherMap Task Execution Started
Guru Meditation Error: Core  0 panic'ed (LoadProhibited). Exception was unhandled.

Any sort of help is appreciated.
Thanks, and Regards

Posted: **Sat Jul 08, 2023 7:17 am**

I found the reason, it was not due to the "_perform()" function, while it was due to the realloc function, still don't know why, instead of crashing it should have returned the NULL pointer.
Anyways I changed the approach to use a big buffer and track the data with indexes, and it works.
The problem is solved, in case someone wanted to comment on something, feel free.
Thanks, and Regards

ESP32 Forum

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