ESP32 BLE Peripheral - how to set long characteristic value?

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1

Hi, I'm new to Arduino. Using an Arduino with ESP32, I have set up a BLE peripheral advertising a service and a characteristic. I need to write 16 bytes to the characteristic value, but I'm stuck on how. For example, I need to write the hex value of 0xFF010000000000000000000000000001 to the characteristic value.

I'm using IDE 2.0.2 and started with the example in File->Examples-> ESP32 BLE Arduino -> BLE_server. Very simply, I want to be able to write the 16 bytes to pCharacteristic in line 30. Not as a string, but as bytes. If I write as a string, the other BLE device receives the ASCII representation of the characters in the string, which is not what I need.

Can anyone help out with this?

Thank you.

/*
    Based on Neil Kolban example for IDF: https://github.com/nkolban/esp32-snippets/blob/master/cpp_utils/tests/BLE%20Tests/SampleServer.cpp
    Ported to Arduino ESP32 by Evandro Copercini
    updates by chegewara
*/

#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"

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
                                       );

  pCharacteristic->setValue("Hello World says Neil");  // <NEED TO WRITE 16 BYTES HERE>
  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);
}
2

Send this character array to the device

char value[16]={0xff,1,0,0,0,0,0,0,0,0,0,0,0,0,0,1};