STM32-IoT-Humdity-Sensor

IoT humidity sensor using STM32 and AHT15
YouTube Tutorial: https://www.youtube.com/watch?v=hdkGWKNdzSs
Try this IoT humidity sensor: http://viktorvano.ddns.net/

Info about ESP8266 12F

ESP8266 12F Boot Modes

Wiring Diagram

Screenshots and Pictures

Web Page screenshot

IoT sensor photo

AHT15 Humidity sensor read registers

Software

WiFi Credentials

Update your WiFi credentials in ESP8266.h:

#define WiFi_Credentials	"AT+CWJAP=\"WiFiSSID\",\"WiFiPASSWORD\"\r\n"

Code snippet of main.c, where:

humidity is measured every 30 seconds
messageHandler() is called when ESP8266 sends a string to STM32
the whole system is reset every 24 hours for safety to prevent ESP8266 firmware from getting stuck (or STM32 also)

  /* USER CODE BEGIN 2 */
  HAL_TIM_Base_Start_IT(&htim2);// 20 ms
  HAL_TIM_Base_Start_IT(&htim3);// 1 s
  HAL_Delay(100);
  AHT15_reset();
  HAL_Delay(100);
  AHT15_init();
  AHT15_read_data();
  __HAL_UART_ENABLE_IT(&huart1, UART_IT_RXNE);
  ESP_Server_Init();
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
	  if(measure_humidity)
	  {
		  AHT15_read_data();
		  measure_humidity = 0;
	  }

	  if(messageHandlerFlag)
	  {
		  messageHandler();
		  messageHandlerFlag = 0;
	  }

	  if(seconds > 86400)// 24 hours
		  NVIC_SystemReset();
  }
  /* USER CODE END 3 */

Code Snipped of ESP8266.c

Function messageHandler() does two things:

responds to "GET" request sent by a browser and sends back a response
auto reconnects to a WiFi Access Point, if disconnected

Response is in sendData(), where:

"HTTP/1.1 200 OK\r\n" says that the response by server is OK
"Content-Length: %i\r\n" gives info about upcomming page html code length
"Content-Type: text/html\r\n\r\n" says that the upcomming code is html (other option for a plain text is "Content-Type: text/plain\r\n\r\n")

In "outputString" is the HTML code, where:

<title>STM32 IoT</title> in the title visible in a web browser tab
<meta http-equiv=\"refresh\" content=\"30\"> makes the webpage auto refresh in 30 seconds
<body><h1>Humidity: %i%%</h1></body> is body of the HTML code

void messageHandler()
{
	__HAL_UART_DISABLE_IT(&huart1, UART_IT_RXNE);
	int position = 0;
	if((position = string_contains((char*)buffer, "GET", buffer_index)) != -1)
	{
		sendData();
	}else if(string_contains((char*)buffer, "+CWJAP:", buffer_index) != -1
			&& (string_contains((char*)buffer, "FAIL", buffer_index) != -1
			|| string_contains((char*)buffer, "DISCONNECT", buffer_index) != -1))
	{
		HAL_UART_Transmit(&huart1, (uint8_t*)WiFi_Credentials, strlen(WiFi_Credentials), 100);
	}
	ESP_Clear_Buffer();
	__HAL_UART_ENABLE_IT(&huart1, UART_IT_RXNE);
}

void sendData()//sends data compatible with a browser
{
	char outputString[300], cipsend[50], response[600];
	memset(outputString, 0, 300);
	memset(cipsend, 0, 50);
	memset(response, 0, 600);

	sprintf(outputString, "<html><head><meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\"><title>STM32 IoT</title><meta http-equiv=\"refresh\" content=\"30\"></head><body><h1>Humidity: %i%%</h1></body></html>", (int)AHT15_relative_humidity);
	sprintf(response, "HTTP/1.1 200 OK\r\nContent-Length: %i\r\nContent-Type: text/html\r\n\r\n%s", strlen(outputString), outputString);
	sprintf(cipsend, "AT+CIPSEND=0,%i\r\n", strlen(response));

	HAL_UART_Transmit(&huart1, (uint8_t*)cipsend, strlen(cipsend), 100);
	HAL_Delay(50);
	HAL_UART_Transmit(&huart1, (uint8_t*)response, strlen(response), 100);
	HAL_Delay(50);
	HAL_UART_Transmit(&huart1, (uint8_t*)"AT+CIPCLOSE=0\r\n", strlen("AT+CIPCLOSE=0\r\n"), 100);
}