The Smartphone Communicates with the Wio Terminal via BLE

#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLE2902.h>
#include <TFT_eSPI.h> // Hardware-specific library
#include <SPI.h>
TFT_eSPI tft = TFT_eSPI();       // Invoke custom library
TFT_eSprite spr = TFT_eSprite(&tft);  // Sprite 

BLEServer *pServer = NULL;
BLECharacteristic * pTxCharacteristic;
bool deviceConnected = false;
bool oldDeviceConnected = false;
String Value11;

#define SERVICE_UUID           "6E400001-B5A3-F393-E0A9-E50E24DCCA9E" // UART service UUID
#define CHARACTERISTIC_UUID_RX "6E400002-B5A3-F393-E0A9-E50E24DCCA9E"
#define CHARACTERISTIC_UUID_TX "6E400003-B5A3-F393-E0A9-E50E24DCCA9E"

class MyServerCallbacks: public BLEServerCallbacks {
    void onConnect(BLEServer* pServer) {
      deviceConnected = true;
      spr.fillSprite(TFT_BLACK);
      spr.createSprite(240, 100);
      spr.setTextColor(TFT_WHITE, TFT_BLACK);
      spr.setFreeFont(&FreeSansBoldOblique12pt7b);
      spr.drawString("Message: ", 20, 70);
      spr.setTextColor(TFT_GREEN, TFT_BLACK);
      spr.drawString("status: connected",10 ,5); 
      spr.pushSprite(0, 0);
    };

    void onDisconnect(BLEServer* pServer) {
      deviceConnected = false;
      Serial.print("123123");
      spr.fillSprite(TFT_BLACK);
      spr.createSprite(240, 100);
      spr.setTextColor(TFT_WHITE, TFT_BLACK);
      spr.setFreeFont(&FreeSansBoldOblique12pt7b);
      spr.drawString("Message: ", 20, 70);
      spr.setTextColor(TFT_RED, TFT_BLACK);
      spr.drawString("status: disconnect",10 ,5); 
      spr.pushSprite(0, 0);
    }
};

class MyCallbacks: public BLECharacteristicCallbacks {
    void onWrite(BLECharacteristic *pCharacteristic) {
      std::string rxValue = pCharacteristic->getValue();
        
        if (rxValue.length() > 0) {
        spr.fillSprite(TFT_BLACK);
        spr.setTextColor(TFT_WHITE, TFT_BLACK);
        spr.setFreeFont(&FreeSansBoldOblique9pt7b);
        for (int i = 0; i < rxValue.length(); i++){
//           Serial.print(rxValue[i]);
           spr.drawString((String)rxValue[i],10 + i*15,0);
        spr.pushSprite(10, 100);
        }
       }
    }
};

void setup() {
  tft.begin();
  tft.init();
  tft.setRotation(3);
  tft.fillScreen(TFT_BLACK);
  
  BLEDevice::init("UART Servicess");

  // 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
  pTxCharacteristic = pService->createCharacteristic(
                    CHARACTERISTIC_UUID_TX,
                    BLECharacteristic::PROPERTY_NOTIFY | BLECharacteristic::PROPERTY_READ
                  );
  pTxCharacteristic->setAccessPermissions(GATT_PERM_READ);      
  pTxCharacteristic->addDescriptor(new BLE2902());

  BLECharacteristic * pRxCharacteristic = pService->createCharacteristic(
                       CHARACTERISTIC_UUID_RX,
                      BLECharacteristic::PROPERTY_WRITE
                      
                    );
  pRxCharacteristic->setAccessPermissions(GATT_PERM_READ | GATT_PERM_WRITE);           

  pRxCharacteristic->setCallbacks(new MyCallbacks());

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

  // Start advertising
  pServer->getAdvertising()->start();
      spr.fillSprite(TFT_BLACK);
      spr.createSprite(240, 100);
      spr.setTextColor(TFT_WHITE, TFT_BLACK);
      spr.setFreeFont(&FreeSansBoldOblique12pt7b);
      spr.drawString("status: disconnect",10 ,5); 
      spr.drawString("Message: ", 20, 70);
      spr.pushSprite(0, 0);
}

void loop() {

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