ESP32 Forum

Posted: **Fri Mar 05, 2021 6:52 am**

I can connect to the server through the BLE scanner application and send the value to the ELEM_UUID characteristic.
And I don’t understand how to write a sketch on the ESP32 client so that he would do the same without a smartphone.
Who understands please write how to do it.
Thank you very much in advance!

Code ESP32 Server:

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#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEServer.h>
 
// See the following for generating UUIDs:
// https://www.uuidgenerator.net/
 
#define SERVICE_UUID        "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"
 
#define ELEM_UUID              "cc46b944-003e-42b6-b836-c4246b8f19a0" // ID 
 
void setup() {
  Serial.begin(115200);
  Serial.println("Starting BLE work!");
 
  BLEDevice::init("Long name works now");
  BLEServer *pServer = BLEDevice::createServer();
  BLEService *pService = pServer->createService(SERVICE_UUID);
  BLECharacteristic *pCharacteristic = pService->createCharacteristic(
                                         CHARACTERISTIC_UUID,
                                         BLECharacteristic::PROPERTY_READ |
                                         BLECharacteristic::PROPERTY_WRITE
                                       );
 
  BLECharacteristic *pElem;
 
  class ElemCallbacs : public BLECharacteristicCallbacks {
  void onWrite(BLECharacteristic *pCharacteristic) {
      std::string value1 = pCharacteristic->getValue();
      Serial.println(value1.c_str());
  }
};
  pElem = pService->createCharacteristic(ELEM_UUID,BLECharacteristic::PROPERTY_READ| BLECharacteristic::PROPERTY_WRITE);
  pElem->setCallbacks(new ElemCallbacs());
  
  pCharacteristic->setValue("Hello World says Neil");
  pService->start();
  // BLEAdvertising *pAdvertising = pServer->getAdvertising();  // this still is working for backward compatibility
  BLEAdvertising *pAdvertising = BLEDevice::getAdvertising();
  pAdvertising->addServiceUUID(SERVICE_UUID);
  pAdvertising->setScanResponse(true);
  pAdvertising->setMinPreferred(0x06);  // functions that help with iPhone connections issue
  pAdvertising->setMinPreferred(0x12);
  BLEDevice::startAdvertising();
  Serial.println("Characteristic defined! Now you can read it in your phone!");
}
 
void loop() {
  // put your main code here, to run repeatedly:
 
  delay(2000);
  
}

ESP32 Forum

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How to send a new characteristic value from the ESP32 client to the esp32 BLE server?