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Monday, December 6, 2021

arduino-esp32: ESP32 + DHT11 temperature & humidity sensor with display on ST7789 and BLE function

Exercise on ESP32 (Arduino framework) work with DHT11 temperature & humidity sensor, with display on ST7789 SPI LCD and also with BLE function.

The DHT11 (or DHT22 and similar) are cheap temperature and humidity sensors. The communicate with a uC is over a single wire.

The electric connection to the ESP32 is very simple, as the DHT series can be powered direct with 3.3V. Only 3 wires are needed: VCC, GND and the data line.

Important is that a 10kΩ or at least 4.7kΩ resistor is needed between the data line and VCC. Sometimes this resistor is already integrated in the module, sometimes its necessary to add it.

ref: https://desire.giesecke.tk/index.php/2018/01/30/esp32-dht11/



Library used:

DHT sensor library for ESPx by beegee_tokyo is used in this exercise.

To display on ST7789 SPI SPI LCD, Adafruit ST7735 and ST7789 Library and Adafruit GFX Library are used. (related: ESP32-C3/arduino-esp32 to display on ST7735 and ST7789 SPI LCDs)


Connection:


	Connection between DHT11 and ESP32 (GPIO#)
	-----------------------------------------------
	DHT11         ESP32
	-----         -----
	VCC*          3V3
	DATA**        32
	NC    
	GND           GND

	* - depends on module, my DHT11 module is 3V3~5V operate. 

	** - depends on your module, maybe you have to add a 
	     pull-up resistor (~10K Ohm) betwee DATA and VCC.

	Connection between ST7789 SPI and ESP32 (GPIO#)
	-----------------------------------------------
	ST7789 SPI    ESP32
	----------    -----
	GND           GND
	VCC           3V3
	SCL           18
	SDA           23
	RES           26
	DC            25
	CS            33
	BLK           3V3
 

Exercise code:

ESP32_DHT_ST789.ino, modified from DHT_ESP32 example of DHT sensor library for ESPx, with interface to ST7789 SPI LCD.

#include "DHTesp.h"
#include <Ticker.h>
#include <Adafruit_GFX.h>    // Core graphics library
#include <Adafruit_ST7789.h> // Hardware-specific library for ST7789
#include <Fonts/FreeMonoBold12pt7b.h>
#include <SPI.h>

#ifndef ESP32
#pragma message(THIS EXAMPLE IS FOR ESP32 ONLY!)
#error Select ESP32 board.
#endif

/**************************************************************/
/* Example how to read DHT sensors from an ESP32 using multi- */
/* tasking.                                                   */
/* This example depends on the Ticker library to wake up      */
/* the task every 5  seconds                                  */
/**************************************************************/

DHTesp dht;

void tempTask(void *pvParameters);
bool getTemperature();
void triggerGetTemp();

/** Task handle for the light value read task */
TaskHandle_t tempTaskHandle = NULL;
/** Ticker for temperature reading */
Ticker tempTicker;
/** Comfort profile */
ComfortState cf;
/** Flag if task should run */
bool tasksEnabled = false;
/** Pin number for DHT11 data pin */
int dhtPin = 32;  //17;

#define TFT_CS        33
#define TFT_RST       26
#define TFT_DC        25
Adafruit_ST7789 tft = Adafruit_ST7789(TFT_CS, TFT_DC, TFT_RST);

bool rqsUpdate = false;
TempAndHumidity updateValues;


/**
 * initTemp
 * Setup DHT library
 * Setup task and timer for repeated measurement
 * @return bool
 *    true if task and timer are started
 *    false if task or timer couldn't be started
 */
bool initTemp() {
  byte resultValue = 0;
  // Initialize temperature sensor
	dht.setup(dhtPin, DHTesp::DHT11);
	Serial.println("DHT initiated");

  // Start task to get temperature
	xTaskCreatePinnedToCore(
			tempTask,                       /* Function to implement the task */
			"tempTask ",                    /* Name of the task */
			4000,                           /* Stack size in words */
			NULL,                           /* Task input parameter */
			5,                              /* Priority of the task */
			&tempTaskHandle,                /* Task handle. */
			1);                             /* Core where the task should run */

  if (tempTaskHandle == NULL) {
    Serial.println("Failed to start task for temperature update");
    return false;
  } else {
    // Start update of environment data every 20 seconds
    tempTicker.attach(5, triggerGetTemp);
  }
  return true;
}

/**
 * triggerGetTemp
 * Sets flag dhtUpdated to true for handling in loop()
 * called by Ticker getTempTimer
 */
void triggerGetTemp() {
  if (tempTaskHandle != NULL) {
	   xTaskResumeFromISR(tempTaskHandle);
  }
}

/**
 * Task to reads temperature from DHT11 sensor
 * @param pvParameters
 *    pointer to task parameters
 */
void tempTask(void *pvParameters) {
	Serial.println("tempTask loop started");
	while (1) // tempTask loop
  {
    if (tasksEnabled) {
      // Get temperature values
			getTemperature();
		}
    // Got sleep again
		vTaskSuspend(NULL);
	}
}

/**
 * getTemperature
 * Reads temperature from DHT11 sensor
 * @return bool
 *    true if temperature could be aquired
 *    false if aquisition failed
*/
bool getTemperature() {
	// Reading temperature for humidity takes about 250 milliseconds!
	// Sensor readings may also be up to 2 seconds 'old' (it's a very slow sensor)
  TempAndHumidity newValues = dht.getTempAndHumidity();
	// Check if any reads failed and exit early (to try again).
	if (dht.getStatus() != 0) {
		Serial.println("DHT11 error status: " + String(dht.getStatusString()));
		return false;
	}

	float heatIndex = dht.computeHeatIndex(newValues.temperature, newValues.humidity);
  float dewPoint = dht.computeDewPoint(newValues.temperature, newValues.humidity);
  float cr = dht.getComfortRatio(cf, newValues.temperature, newValues.humidity);

  String comfortStatus;
  switch(cf) {
    case Comfort_OK:
      comfortStatus = "Comfort_OK";
      break;
    case Comfort_TooHot:
      comfortStatus = "Comfort_TooHot";
      break;
    case Comfort_TooCold:
      comfortStatus = "Comfort_TooCold";
      break;
    case Comfort_TooDry:
      comfortStatus = "Comfort_TooDry";
      break;
    case Comfort_TooHumid:
      comfortStatus = "Comfort_TooHumid";
      break;
    case Comfort_HotAndHumid:
      comfortStatus = "Comfort_HotAndHumid";
      break;
    case Comfort_HotAndDry:
      comfortStatus = "Comfort_HotAndDry";
      break;
    case Comfort_ColdAndHumid:
      comfortStatus = "Comfort_ColdAndHumid";
      break;
    case Comfort_ColdAndDry:
      comfortStatus = "Comfort_ColdAndDry";
      break;
    default:
      comfortStatus = "Unknown:";
      break;
  };

  Serial.println(" T:" + String(newValues.temperature)
                + " H:" + String(newValues.humidity) 
                + " I:" + String(heatIndex) 
                + " D:" + String(dewPoint) 
                + " " + comfortStatus);
	rqsUpdate = true;
	updateValues = newValues;
	return true;
}

void setup()
{
  Serial.begin(115200);
  Serial.println();
  Serial.println("DHT ESP32 example with tasks");

  //init DHT
  initTemp();
  // Signal end of setup() to tasks
  tasksEnabled = true;

  //init ST7789
  tft.init(240, 320);           // Init ST7789 320x240
  tft.setRotation(3);
  tft.setFont(&FreeMonoBold12pt7b);
  tft.setTextWrap(true);
  
  tft.fillScreen(ST77XX_RED);
  delay(300);
  tft.fillScreen(ST77XX_GREEN);
  delay(300);
  tft.fillScreen(ST77XX_BLUE);
  delay(300);
  tft.fillScreen(ST77XX_BLACK);
  delay(300);

  tft.setCursor(0, 0);
  tft.setTextColor(ST77XX_RED);
  
  tft.setCursor(0, 0);
  tft.setTextColor(ST77XX_RED);
  tft.print("\n");
  tft.print("ESP32 + DHT11 + ST7789\n");

}

void loop() {
  if (!tasksEnabled) {
    // Wait 2 seconds to let system settle down
    delay(2000);
    // Enable task that will read values from the DHT sensor
    tasksEnabled = true;
    if (tempTaskHandle != NULL) {
			vTaskResume(tempTaskHandle);
		}
  }

  if(rqsUpdate){

    tft.fillRect(10, 30, 300, 53, ST77XX_BLACK);
    
    tft.setCursor(5, 50);
    tft.setTextColor(ST77XX_WHITE);
    tft.print(" temperature:  " + String(updateValues.temperature));
    tft.setCursor(5, 75);
    tft.setTextColor(ST77XX_WHITE);
    tft.print(" humidity:     " + String(updateValues.humidity));
    
    Serial.println(" T:" + String(updateValues.temperature) + " H:" + String(updateValues.humidity));
    rqsUpdate = false;
  }
  
  yield();
}


ESP32_DHT_ST789_graphic.ino, display on ST7789 SPI LCD with graph.
/*
 * Execise run on ESP32 (ESP32-DevKitC V4) with arduino-esp32 2.0.1,
 * read DHT11 Humidity & Temperature Sensor,
 * and display on ST7789 SPI TFT, 2" IPS 240x320, with graph.
 * 
 * Library needed: 
 * - DHT sensor library for ESPx by beegee_tokyo
 * - Adafruit ST7735 and ST7789 Library by Adafruit 
 * - Adafruit GFX Library by Adafruit
 * 
 *  Modify from examples DHT_ESP32 of DHT sensor library for ESPx
 *  
 *  Connection between DHT11 and ESP32 (GPIO#)
 *  -----------------------------------------------
 *  DHT11         ESP32
 *  -----         -----
 *  VCC*          3V3
 *  DATA**        32
 *  NC    
 *  GND           GND
 *  
 *  * - depends on module, my DHT11 module is 3V3~5V operate. 
 *  
 *  ** - depends on your module, maybe you have to add a 
 *  pull-up resistor (~10K Ohm) betwee DATA and VCC.
 *  
 *  Connection between ST7789 SPI and ESP32 (GPIO#)
 *  -----------------------------------------------
 *  ST7789 SPI    ESP32
 *  ----------    -----
 *  GND           GND
 *  VCC           3V3
 *  SCL           18
 *  SDA           23
 *  RES           26
 *  DC            25
 *  CS            33
 *  BLK           3V3
 *  
 */
#include "DHTesp.h"
#include <Ticker.h>
#include <Adafruit_GFX.h>    // Core graphics library
#include <Adafruit_ST7789.h> // Hardware-specific library for ST7789
#include <Fonts/FreeMonoBold12pt7b.h>
#include <SPI.h>

#ifndef ESP32
#pragma message(THIS EXAMPLE IS FOR ESP32 ONLY!)
#error Select ESP32 board.
#endif

DHTesp dht;

void tempTask(void *pvParameters);
bool getTemperature();
void triggerGetTemp();

/** Task handle for the light value read task */
TaskHandle_t tempTaskHandle = NULL;
/** Ticker for temperature reading */
Ticker tempTicker;
/** Comfort profile */
ComfortState cf;
/** Flag if task should run */
bool tasksEnabled = false;
/** Pin number for DHT11 data pin */
int dhtPin = 32;  //17;

//hardware SPI MOSI   23
//hardware SPI SCK    18
#define TFT_CS        33
#define TFT_RST       26
#define TFT_DC        25
Adafruit_ST7789 tft = Adafruit_ST7789(TFT_CS, TFT_DC, TFT_RST);

bool rqsUpdate = false;
TempAndHumidity updateValues;

unsigned long prvUpdateMillis;

#define FRAME_TOPX    0
#define FRAME_TOPY    200
#define FRAME_WIDTH   240
#define FRAME_HEIGHT  100
#define FRAME_BOTTOMY FRAME_TOPY + FRAME_HEIGHT
#define SCR_HEIGHT    320

int idx = 0;
#define IDX_MAX     240

/**
 * initTemp
 * Setup DHT library
 * Setup task and timer for repeated measurement
 * @return bool
 *    true if task and timer are started
 *    false if task or timer couldn't be started
 */
bool initTemp() {
  byte resultValue = 0;
  // Initialize temperature sensor
	dht.setup(dhtPin, DHTesp::DHT11);
	Serial.println("DHT initiated");

  // Start task to get temperature
	xTaskCreatePinnedToCore(
			tempTask,                       /* Function to implement the task */
			"tempTask ",                    /* Name of the task */
			4000,                           /* Stack size in words */
			NULL,                           /* Task input parameter */
			5,                              /* Priority of the task */
			&tempTaskHandle,                /* Task handle. */
			1);                             /* Core where the task should run */

  if (tempTaskHandle == NULL) {
    Serial.println("Failed to start task for temperature update");
    return false;
  } else {
    // Start update of environment data every XX seconds
    tempTicker.attach(2, triggerGetTemp);
  }
  return true;
}

/**
 * triggerGetTemp
 * Sets flag dhtUpdated to true for handling in loop()
 * called by Ticker getTempTimer
 */
void triggerGetTemp() {
  if (tempTaskHandle != NULL) {
	   xTaskResumeFromISR(tempTaskHandle);
  }
}

/**
 * Task to reads temperature from DHT11 sensor
 * @param pvParameters
 *    pointer to task parameters
 */
void tempTask(void *pvParameters) {
	Serial.println("tempTask loop started");
	while (1) // tempTask loop
  {
    if (tasksEnabled) {
      // Get temperature values
			getTemperature();
		}
    // Got sleep again
		vTaskSuspend(NULL);
	}
}

/**
 * getTemperature
 * Reads temperature from DHT11 sensor
 * @return bool
 *    true if temperature could be aquired
 *    false if aquisition failed
*/
bool getTemperature() {
	// Reading temperature for humidity takes about 250 milliseconds!
	// Sensor readings may also be up to 2 seconds 'old' (it's a very slow sensor)
  TempAndHumidity newValues = dht.getTempAndHumidity();
	// Check if any reads failed and exit early (to try again).
	if (dht.getStatus() != 0) {
		Serial.println("DHT11 error status: " + String(dht.getStatusString()));
		return false;
	}

	float heatIndex = dht.computeHeatIndex(newValues.temperature, newValues.humidity);
  float dewPoint = dht.computeDewPoint(newValues.temperature, newValues.humidity);
  float cr = dht.getComfortRatio(cf, newValues.temperature, newValues.humidity);

  String comfortStatus;
  switch(cf) {
    case Comfort_OK:
      comfortStatus = "Comfort_OK";
      break;
    case Comfort_TooHot:
      comfortStatus = "Comfort_TooHot";
      break;
    case Comfort_TooCold:
      comfortStatus = "Comfort_TooCold";
      break;
    case Comfort_TooDry:
      comfortStatus = "Comfort_TooDry";
      break;
    case Comfort_TooHumid:
      comfortStatus = "Comfort_TooHumid";
      break;
    case Comfort_HotAndHumid:
      comfortStatus = "Comfort_HotAndHumid";
      break;
    case Comfort_HotAndDry:
      comfortStatus = "Comfort_HotAndDry";
      break;
    case Comfort_ColdAndHumid:
      comfortStatus = "Comfort_ColdAndHumid";
      break;
    case Comfort_ColdAndDry:
      comfortStatus = "Comfort_ColdAndDry";
      break;
    default:
      comfortStatus = "Unknown:";
      break;
  };

  Serial.println(" T:" + String(newValues.temperature)
                + " H:" + String(newValues.humidity) 
                + " I:" + String(heatIndex) 
                + " D:" + String(dewPoint) 
                + " " + comfortStatus);
	rqsUpdate = true;
	updateValues = newValues;
	return true;
}

void setup()
{
  Serial.begin(115200);
  Serial.println();
  Serial.println("DHT ESP32 example with tasks");

  //init DHT
  initTemp();
  // Signal end of setup() to tasks
  tasksEnabled = true;

  //init ST7789
  tft.init(240, 320);           // Init ST7789 320x240
  tft.setRotation(2);
  tft.setFont(&FreeMonoBold12pt7b);
  tft.setTextWrap(true);
  
  tft.fillScreen(ST77XX_RED);
  delay(300);
  tft.fillScreen(ST77XX_GREEN);
  delay(300);
  tft.fillScreen(ST77XX_BLUE);
  delay(300);

  tft.setCursor(0, 0);
  tft.setTextColor(ST77XX_RED);
  tft.print("\n");
  tft.print("ESP32 + DHT11 + ST7789\n");

  prvUpdateMillis = millis();

}

void loop() {
  if (!tasksEnabled) {
    // Wait 2 seconds to let system settle down
    delay(2000);
    // Enable task that will read values from the DHT sensor
    tasksEnabled = true;
    if (tempTaskHandle != NULL) {
			vTaskResume(tempTaskHandle);
		}
  }

  if(rqsUpdate){

    unsigned long curUpdateMillis = millis();

    tft.fillRect(0, 53, 240, 75, ST77XX_BLUE );
    
    tft.setCursor(0, 70);
    tft.setTextColor(ST77XX_WHITE);
    tft.print(" temp.: " + String(updateValues.temperature));
    tft.setCursor(0, 95);
    tft.setTextColor(ST77XX_WHITE);
    tft.print(" humi.: " + String(updateValues.humidity));
    tft.setCursor(0, 115);
    tft.setTextColor(ST77XX_WHITE);
    tft.print(" mills.: " + String(curUpdateMillis-prvUpdateMillis));
    prvUpdateMillis = curUpdateMillis;


    if(idx==0){
      tft.fillRect(FRAME_TOPX, FRAME_TOPY, 
                  FRAME_WIDTH, SCR_HEIGHT-FRAME_TOPY, 
                  ST77XX_BLUE);
    }
  
    tft.drawLine(
      FRAME_TOPX+idx, FRAME_BOTTOMY, 
      FRAME_TOPX+idx, FRAME_BOTTOMY-(int)updateValues.temperature, 
      ST77XX_WHITE);

    idx++;
    if(idx >= IDX_MAX)
      idx = 0;
    
    Serial.println(" T:" + String(updateValues.temperature) + " H:" + String(updateValues.humidity));
    rqsUpdate = false;
  }
  
  yield();
}


ESP32_DHT_ST789_graphic_BLE.ino, with display on ST7789 SPI LCD, and BLE function added.
/*
   Execise run on ESP32 (ESP32-DevKitC V4) with arduino-esp32 2.0.1,
   read DHT11 Humidity & Temperature Sensor,
   and display on ST7789 SPI TFT, 2" IPS 240x320, with graph.
   BLE function added.

   Library needed:
   - DHT sensor library for ESPx by beegee_tokyo
   - Adafruit ST7735 and ST7789 Library by Adafruit
   - Adafruit GFX Library by Adafruit

    Modify from examples DHT_ESP32 of DHT sensor library for ESPx

    Connection between DHT11 and ESP32 (GPIO#)
    -----------------------------------------------
    DHT11         ESP32
    -----         -----
    VCC*          3V3
    DATA**        32
    NC
    GND           GND

 *  * - depends on module, my DHT11 module is 3V3~5V operate.

 *  ** - depends on your module, maybe you have to add a
    pull-up resistor (~10K Ohm) betwee DATA and VCC.

    Connection between ST7789 SPI and ESP32 (GPIO#)
    -----------------------------------------------
    ST7789 SPI    ESP32
    ----------    -----
    GND           GND
    VCC           3V3
    SCL           18
    SDA           23
    RES           26
    DC            25
    CS            33
    BLK           3V3

*/
#include "DHTesp.h"
#include <Ticker.h>
#include <Adafruit_GFX.h>    // Core graphics library
#include <Adafruit_ST7789.h> // Hardware-specific library for ST7789
#include <Fonts/FreeMonoBold12pt7b.h>
#include <SPI.h>

#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLEUtils.h>
#include <BLE2902.h>

#ifndef ESP32
#pragma message(THIS EXAMPLE IS FOR ESP32 ONLY!)
#error Select ESP32 board.
#endif

DHTesp dht;

void tempTask(void *pvParameters);
bool getTemperature();
void triggerGetTemp();

/** Task handle for the light value read task */
TaskHandle_t tempTaskHandle = NULL;
/** Ticker for temperature reading */
Ticker tempTicker;
/** Comfort profile */
ComfortState cf;
/** Flag if task should run */
bool tasksEnabled = false;
/** Pin number for DHT11 data pin */
int dhtPin = 32;  //17;

//hardware SPI MOSI   23
//hardware SPI SCK    18
#define TFT_CS        33
#define TFT_RST       26
#define TFT_DC        25
Adafruit_ST7789 tft = Adafruit_ST7789(TFT_CS, TFT_DC, TFT_RST);

bool rqsUpdate = false;
TempAndHumidity updateValues;

unsigned long prvUpdateMillis;

#define FRAME_TOPX    0
#define FRAME_TOPY    200
#define FRAME_WIDTH   240
#define FRAME_HEIGHT  100
#define FRAME_BOTTOMY FRAME_TOPY + FRAME_HEIGHT
#define SCR_HEIGHT    320

int idx = 0;
#define IDX_MAX     240

BLEServer* pServer = NULL;
BLECharacteristic* pCharacteristic = NULL;
BLECharacteristic* pChar_temp = NULL;
BLECharacteristic* pChar_humi = NULL;
bool deviceConnected = false;
bool oldDeviceConnected = false;

// See the following for generating UUIDs:
// https://www.uuidgenerator.net/

#define SERVICE_UUID "FC8601FC-7829-407B-9C2E-4D3F117DFF2D"
#define CHAR_UUID_TEMP "0FD31907-35AE-4BB0-8AB1-51F98C05B326"
#define CHAR_UUID_HUMI "D01D3AF7-818D-4A90-AECF-0E1EC48AA5F0"

class MyServerCallbacks: public BLEServerCallbacks {
    void onConnect(BLEServer* pServer) {
      deviceConnected = true;
      BLEDevice::startAdvertising();
      Serial.println("MyServerCallbacks.onConnect");
    };

    void onDisconnect(BLEServer* pServer) {
      deviceConnected = false;
      Serial.println("MyServerCallbacks.onDisconnect");
    }
};

/**
   initTemp
   Setup DHT library
   Setup task and timer for repeated measurement
   @return bool
      true if task and timer are started
      false if task or timer couldn't be started
*/
bool initTemp() {
  byte resultValue = 0;
  // Initialize temperature sensor
  dht.setup(dhtPin, DHTesp::DHT11);
  Serial.println("DHT initiated");

  // Start task to get temperature
  xTaskCreatePinnedToCore(
    tempTask,                       /* Function to implement the task */
    "tempTask ",                    /* Name of the task */
    4000,                           /* Stack size in words */
    NULL,                           /* Task input parameter */
    5,                              /* Priority of the task */
    &tempTaskHandle,                /* Task handle. */
    1);                             /* Core where the task should run */

  if (tempTaskHandle == NULL) {
    Serial.println("Failed to start task for temperature update");
    return false;
  } else {
    // Start update of environment data every XX seconds
    tempTicker.attach(2, triggerGetTemp);
  }
  return true;
}

/**
   triggerGetTemp
   Sets flag dhtUpdated to true for handling in loop()
   called by Ticker getTempTimer
*/
void triggerGetTemp() {
  if (tempTaskHandle != NULL) {
    xTaskResumeFromISR(tempTaskHandle);
  }
}

/**
   Task to reads temperature from DHT11 sensor
   @param pvParameters
      pointer to task parameters
*/
void tempTask(void *pvParameters) {
  Serial.println("tempTask loop started");
  while (1) // tempTask loop
  {
    if (tasksEnabled) {
      // Get temperature values
      getTemperature();
    }
    // Got sleep again
    vTaskSuspend(NULL);
  }
}

/**
   getTemperature
   Reads temperature from DHT11 sensor
   @return bool
      true if temperature could be aquired
      false if aquisition failed
*/
bool getTemperature() {
  // Reading temperature for humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (it's a very slow sensor)
  TempAndHumidity newValues = dht.getTempAndHumidity();
  // Check if any reads failed and exit early (to try again).
  if (dht.getStatus() != 0) {
    Serial.println("DHT11 error status: " + String(dht.getStatusString()));
    return false;
  }

  rqsUpdate = true;
  updateValues = newValues;
  return true;
}

void setup()
{
  Serial.begin(115200);
  Serial.println();
  Serial.println("DHT ESP32 example with tasks");

  //init DHT
  initTemp();
  // Signal end of setup() to tasks
  tasksEnabled = true;

  //init BLE
  // Create the BLE Device
  BLEDevice::init("ESP32-DHT11");

  // Create the BLE Server
  pServer = BLEDevice::createServer();

  pServer->setCallbacks(new MyServerCallbacks());

  // Create the BLE Service
  BLEService *pService = pServer->createService(SERVICE_UUID);

  // Create a BLE Characteristic for temp and humi
  pChar_temp = pService->createCharacteristic(
                 CHAR_UUID_TEMP,
                 BLECharacteristic::PROPERTY_READ   |
                 BLECharacteristic::PROPERTY_WRITE  |
                 BLECharacteristic::PROPERTY_NOTIFY |
                 BLECharacteristic::PROPERTY_INDICATE
               );
  pChar_humi = pService->createCharacteristic(
                 CHAR_UUID_HUMI,
                 BLECharacteristic::PROPERTY_READ   |
                 BLECharacteristic::PROPERTY_WRITE  |
                 BLECharacteristic::PROPERTY_NOTIFY |
                 BLECharacteristic::PROPERTY_INDICATE
               );

  pChar_temp->addDescriptor(new BLE2902());
  pChar_humi->addDescriptor(new BLE2902());

  // Start the service
  pService->start();

  // Start advertising
  BLEAdvertising *pAdvertising = BLEDevice::getAdvertising();
  pAdvertising->addServiceUUID(SERVICE_UUID);
  pAdvertising->setScanResponse(false);
  pAdvertising->setMinPreferred(0x0);  // set value to 0x00 to not advertise this parameter
  BLEDevice::startAdvertising();
  Serial.println("Waiting a client connection to notify...");


  //init ST7789
  tft.init(240, 320);           // Init ST7789 320x240
  tft.setRotation(2);
  tft.setFont(&FreeMonoBold12pt7b);
  tft.setTextWrap(true);

  tft.fillScreen(ST77XX_RED);
  delay(300);
  tft.fillScreen(ST77XX_GREEN);
  delay(300);
  tft.fillScreen(ST77XX_BLUE);
  delay(300);

  tft.setCursor(0, 0);
  tft.setTextColor(ST77XX_RED);
  tft.print("\n");
  tft.print("ESP32 + DHT11 + ST7789\n");

  prvUpdateMillis = millis();

}

void loop() {
  if (!tasksEnabled) {
    // Wait 2 seconds to let system settle down
    delay(2000);
    // Enable task that will read values from the DHT sensor
    tasksEnabled = true;
    if (tempTaskHandle != NULL) {
      vTaskResume(tempTaskHandle);
    }
  }

  if (rqsUpdate) {

    unsigned long curUpdateMillis = millis();

    tft.fillRect(0, 53, 240, 75, ST77XX_BLUE );

    tft.setCursor(0, 70);
    tft.setTextColor(ST77XX_WHITE);
    tft.print(" temp.: " + String(updateValues.temperature));
    tft.setCursor(0, 95);
    tft.setTextColor(ST77XX_WHITE);
    tft.print(" humi.: " + String(updateValues.humidity));
    tft.setCursor(0, 115);
    tft.setTextColor(ST77XX_WHITE);
    tft.print(" mills.: " + String(curUpdateMillis - prvUpdateMillis));
    prvUpdateMillis = curUpdateMillis;


    if (idx == 0) {
      tft.fillRect(FRAME_TOPX, FRAME_TOPY,
                   FRAME_WIDTH, SCR_HEIGHT - FRAME_TOPY,
                   ST77XX_BLUE);
    }

    tft.drawLine(
      FRAME_TOPX + idx, FRAME_BOTTOMY,
      FRAME_TOPX + idx, FRAME_BOTTOMY - (int)updateValues.temperature,
      ST77XX_WHITE);

    idx++;
    if (idx >= IDX_MAX)
      idx = 0;

    char bufTemp[5];
    char bufHumi[5];
    //convert floating point value to String
    dtostrf(updateValues.temperature, 0, 2, bufTemp);
    dtostrf(updateValues.humidity, 0, 2, bufHumi);

    pChar_temp->setValue((uint8_t*)bufTemp, 5);
    pChar_temp->notify();
    pChar_humi->setValue((uint8_t*)bufHumi, 5);
    pChar_humi->notify();

    //Serial.println(" T:" + String(updateValues.temperature) + " H:" + String(updateValues.humidity));
    rqsUpdate = false;


  }

  // disconnecting
  if (!deviceConnected && oldDeviceConnected) {
    Serial.println("disconnecting");
    delay(500); // give the bluetooth stack the chance to get things ready
    pServer->startAdvertising(); // restart advertising
    Serial.println("start advertising");
    oldDeviceConnected = deviceConnected;
  }
  // connecting
  if (deviceConnected && !oldDeviceConnected) {
    Serial.println("connecting");
    // do stuff here on connecting
    oldDeviceConnected = deviceConnected;
  }

  yield();
}

ex_pyBLE.py, Python3 code run on Raspberry Pi 4B running 32-bit Raspberry Pi OS (bullseye), to monitor temperature & humidity from ESP32_DHT_ST789_graphic_BLE.ino.

# To install bluepy for Python3:
# $ sudo pip3 install bluepy
from bluepy import btle

from datetime import datetime

class MyDelegate(btle.DefaultDelegate):
    def __init__(self, handleTemp, handleHumi):
        self.handleTemp = handleTemp
        self.handleHumi = handleHumi
        btle.DefaultDelegate.__init__(self)
        # ... initialise here

    def handleNotification(self, cHandle, data):
        now = datetime.now()
        current_time = now.strftime("%H:%M:%S")

        if cHandle == self.handleTemp:
            print("temp:", data, "@", current_time)
        elif cHandle == self.handleHumi:
            print("humi:", data, "@", current_time)

# Initialisation  -------
address = "24:0A:C4:E8:0F:9A"
service_uuid = "FC8601FC-7829-407B-9C2E-4D3F117DFF2D"
char_uuid_temp = "0FD31907-35AE-4BB0-8AB1-51F98C05B326"
char_uuid_humi = "D01D3AF7-818D-4A90-AECF-0E1EC48AA5F0"

p = btle.Peripheral(address)
#p.setDelegate(MyDelegate())

# Setup to turn notifications on, e.g.
svc = p.getServiceByUUID(service_uuid)
ch_temp = svc.getCharacteristics(char_uuid_temp)[0]
ch_humi = svc.getCharacteristics(char_uuid_humi)[0]
print("ch_temp handle", ch_temp.getHandle())
print("ch_humi handle", ch_humi.getHandle())
p.setDelegate(MyDelegate(ch_temp.getHandle(), ch_humi.getHandle()))
"""
Remark for setup_data for bluepy noification-
Actually I don't understand how come setup_data = b"\x01\x00",
and ch.valHandle + 1.
Just follow suggestion by searching in internet:
https://stackoverflow.com/questions/32807781/
ble-subscribe-to-notification-using-gatttool-or-bluepy
"""
setup_data = b"\x01\x00"
#ch.write(setup_data)
p.writeCharacteristic(ch_temp.valHandle + 1, setup_data)
p.writeCharacteristic(ch_humi.valHandle + 1, setup_data)

print("=== Main Loop ===")

while True:
    if p.waitForNotifications(1.0):
        # handleNotification() was called
        continue

    #print("Waiting...")
    # Perhaps do something else here



remark:
BUT, I found that ex_pyBLE.py run on Raspberry Pi is sometimes unstable; with error of:
luepy.btle.BTLEDisconnectError: Failed to connect to peripheral ...




Next:
~ BLE between ESP32/ESP32C3 (arduino-esp32), notify DHT11 reading of temperature & humidity.


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