ESP32 bluetooth

Posts: 10
Joined: Mon Nov 04, 2019 10:04 pm

Re: ESP32 bluetooth

Postby vcch75 » Fri Nov 15, 2019 7:05 am

Yes i have these devices advertising. What i need is and android code for esp32 spanning devices by name, and connecting the ones matching specific names.

But the pin code which runs well in android is a server not a client. And the android scan sample code does not find the name of most devices (not my PC nor my phone). And the other codes you mentionned dont run with android.

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Joined: Wed Jun 14, 2017 9:00 pm

Re: ESP32 bluetooth

Postby chegewara » Fri Nov 15, 2019 10:53 am

Its because even if you turn on bluetooth on PC it wont start advertising by itself, you have to turn on advertising (its called visibility, or something like that). The same situation is with smartphones, it wont be visible as BLE device unless your application or system driver starts advertising.

Posts: 10
Joined: Mon Nov 04, 2019 10:04 pm

Re: ESP32 bluetooth

Postby vcch75 » Sat Nov 16, 2019 9:06 am

Yes I know and I have done it.

The device appears in the scan when I am using, but its name seems hidden. So my questions are:
1) What do I have to add to the code to get the names (most of them are not displayed) ?
2) How do I select devices by NAME and not by complex uids so that the ESP32 can initiate the connection (I want to receive a connection invitation to my phone AND my computer, and connect to the first one answering)

Code: Select all

 * A BLE client example that is rich in capabilities.
 * There is a lot new capabilities implemented.
 * author unknown
 * updated by chegewara

#include "BLEDevice.h"
#include "BLEScan.h"

// The remote service we wish to connect to.
static BLEUUID serviceUUID("4fafc201-1fb5-459e-8fcc-c5c9c331914b");
// The characteristic of the remote service we are interested in.
static BLEUUID    charUUID("beb5483e-36e1-4688-b7f5-ea07361b26a8");

static boolean doConnect = false;
static boolean connected = false;
static boolean doScan = false;
static BLERemoteCharacteristic* pRemoteCharacteristic;
static BLEAdvertisedDevice* myDevice;

static void notifyCallback(
  BLERemoteCharacteristic* pBLERemoteCharacteristic,
  uint8_t* pData,
  size_t length,
  bool isNotify) {
    Serial.print("Notify callback for characteristic ");
    Serial.print(" of data length ");
    Serial.print("data: ");

class MyClientCallback : public BLEClientCallbacks {
  void onConnect(BLEClient* pclient) {

  void onDisconnect(BLEClient* pclient) {
    connected = false;

bool connectToServer() {
    Serial.print("Forming a connection to ");
    BLEClient*  pClient  = BLEDevice::createClient();
    Serial.println(" - Created client");

    pClient->setClientCallbacks(new MyClientCallback());

    // Connect to the remove BLE Server.
    pClient->connect(myDevice);  // if you pass BLEAdvertisedDevice instead of address, it will be recognized type of peer device address (public or private)
    Serial.println(" - Connected to server");

    // Obtain a reference to the service we are after in the remote BLE server.
    BLERemoteService* pRemoteService = pClient->getService(serviceUUID);
    if (pRemoteService == nullptr) {
      Serial.print("Failed to find our service UUID: ");
      return false;
    Serial.println(" - Found our service");

    // Obtain a reference to the characteristic in the service of the remote BLE server.
    pRemoteCharacteristic = pRemoteService->getCharacteristic(charUUID);
    if (pRemoteCharacteristic == nullptr) {
      Serial.print("Failed to find our characteristic UUID: ");
      return false;
    Serial.println(" - Found our characteristic");

    // Read the value of the characteristic.
    if(pRemoteCharacteristic->canRead()) {
      std::string value = pRemoteCharacteristic->readValue();
      Serial.print("The characteristic value was: ");


    connected = true;
 * Scan for BLE servers and find the first one that advertises the service we are looking for.
class MyAdvertisedDeviceCallbacks: public BLEAdvertisedDeviceCallbacks {
   * Called for each advertising BLE server.
  void onResult(BLEAdvertisedDevice advertisedDevice) {
    Serial.print("BLE Advertised Device found: ");

    // We have found a device, let us now see if it contains the service we are looking for.
    if (advertisedDevice.haveServiceUUID() && advertisedDevice.isAdvertisingService(serviceUUID)) {

      myDevice = new BLEAdvertisedDevice(advertisedDevice);
      doConnect = true;
      doScan = true;

    } // Found our server
  } // onResult
}; // MyAdvertisedDeviceCallbacks

void setup() {
  Serial.println("Starting Arduino BLE Client application...");

  // Retrieve a Scanner and set the callback we want to use to be informed when we
  // have detected a new device.  Specify that we want active scanning and start the
  // scan to run for 5 seconds.
  BLEScan* pBLEScan = BLEDevice::getScan();
  pBLEScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks());
  pBLEScan->start(5, false);
} // End of setup.

// This is the Arduino main loop function.
void loop() {

  // If the flag "doConnect" is true then we have scanned for and found the desired
  // BLE Server with which we wish to connect.  Now we connect to it.  Once we are 
  // connected we set the connected flag to be true.
  if (doConnect == true) {
    if (connectToServer()) {
      Serial.println("We are now connected to the BLE Server.");
    } else {
      Serial.println("We have failed to connect to the server; there is nothin more we will do.");
    doConnect = false;

  // If we are connected to a peer BLE Server, update the characteristic each time we are reached
  // with the current time since boot.
  if (connected) {
    String newValue = "Time since boot: " + String(millis()/1000);
    Serial.println("Setting new characteristic value to \"" + newValue + "\"");
    // Set the characteristic's value to be the array of bytes that is actually a string.
    pRemoteCharacteristic->writeValue(newValue.c_str(), newValue.length());
  }else if(doScan){
    BLEDevice::getScan()->start(0);  // this is just eample to start scan after disconnect, most likely there is better way to do it in arduino
  delay(1000); // Delay a second between loops.
} // End of loop
Last edited by vcch75 on Sat Nov 16, 2019 9:39 am, edited 1 time in total.

Posts: 10
Joined: Mon Nov 04, 2019 10:04 pm

Re: ESP32 bluetooth

Postby vcch75 » Sat Nov 16, 2019 9:09 am

In fact my PC does not appear in the scan (my phone does), but if I advertise the ESP32 as server, the PC can see it and connect. Then everything works (i tried as an HIFD device). My PC appears when I use a bluetooth scanner, though and on my phone's devices to connect list.

My phone appears both in the ESP32 scan. So lets put aside the PC : how can I make the ESP32 scan, find my phone by name, and have the ESP32 initiating a pairing (ie s that the phone accepts, but does not have to look for it) ?

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