Wednesday, January 20, 2021

ESP32 BLE_notify example, handle Notification with Python/Raspberry Pi.

ESP32 BLE_notify example create a BLE server that, once we receive a connection, will send periodic notifications.

In ESP32 side, load
Examples > ESP32 BLE Arduino > BLE_notify

Tested on ESP32-DevKitC V4 in my case.

I implemented a simple Python code run on Raspberry Pi, connect to ESP32 and handle notification.

    Based on Neil Kolban example for IDF:
    Ported to Arduino ESP32 by Evandro Copercini
    updated by chegewara

   Create a BLE server that, once we receive a connection, will send periodic notifications.
   The service advertises itself as: 4fafc201-1fb5-459e-8fcc-c5c9c331914b
   And has a characteristic of: beb5483e-36e1-4688-b7f5-ea07361b26a8

   The design of creating the BLE server is:
   1. Create a BLE Server
   2. Create a BLE Service
   3. Create a BLE Characteristic on the Service
   4. Create a BLE Descriptor on the characteristic
   5. Start the service.
   6. Start advertising.

   A connect hander associated with the server starts a background task that performs notification
   every couple of seconds.
#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLEUtils.h>
#include <BLE2902.h>

BLEServer* pServer = NULL;
BLECharacteristic* pCharacteristic = NULL;
bool deviceConnected = false;
bool oldDeviceConnected = false;
uint32_t value = 0;

// See the following for generating UUIDs:

#define SERVICE_UUID        "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"

class MyServerCallbacks: public BLEServerCallbacks {
    void onConnect(BLEServer* pServer) {
      deviceConnected = true;

    void onDisconnect(BLEServer* pServer) {
      deviceConnected = false;

void setup() {

  // Create the BLE Device

  // 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
  pCharacteristic = pService->createCharacteristic(
                      BLECharacteristic::PROPERTY_READ   |
                      BLECharacteristic::PROPERTY_WRITE  |
                      BLECharacteristic::PROPERTY_NOTIFY |

  // Create a BLE Descriptor
  pCharacteristic->addDescriptor(new BLE2902());

  // Start the service

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

void loop() {
    // notify changed value
    if (deviceConnected) {
        pCharacteristic->setValue((uint8_t*)&value, 4);
        delay(3); // bluetooth stack will go into congestion, if too many packets are sent, in 6 hours test i was able to go as low as 3ms
    // disconnecting
    if (!deviceConnected && oldDeviceConnected) {
        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) {
        // do stuff here on connecting
        oldDeviceConnected = deviceConnected;


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