Description
Hardware:
Board: ESP32 dev board
Core Installation version: 1.0.4
IDE name: Platform.io
Flash Frequency: 40Mhz
PSRAM enabled: no
Upload Speed: 460800
Computer OS: Windows 7
Description:
@chegewara
I am working on a BLE UART connection between Android and ESP32.
After connection established, it takes some time before the Android app is enabling notification on the UartTX characteristic. On the ESP32 I found no way to get informed if and when the BLE client enabled notifications. If the ESP32 notifies data immediately after a connection is established, the data is lost, because the Android app is not notified about it.
What I would need is a callback (or flag to test) that tells me that the Android app has enabled notifications on the characteristic. On nRF52 Arduino is a callback for the CCCD requests from the client.
Maybe I am blind, but I went through the BLE library up and down, but I cannot find anything that would give me this information.
Sketch: BLE Uart example
#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLEUtils.h>
#include <BLE2902.h>
BLEServer *pServer = NULL;
BLECharacteristic *pTxCharacteristic;
bool deviceConnected = false;
bool oldDeviceConnected = false;
uint8_t txValue = 0;
// See the following for generating UUIDs:
// https://www.uuidgenerator.net/
#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;
};
void onDisconnect(BLEServer *pServer)
{
deviceConnected = false;
}
};
class MyCallbacks : public BLECharacteristicCallbacks
{
void onWrite(BLECharacteristic *pCharacteristic)
{
std::string rxValue = pCharacteristic->getValue();
if (rxValue.length() > 0)
{
Serial.println("*********");
Serial.print("Received Value: ");
for (int i = 0; i < rxValue.length(); i++)
Serial.print(rxValue[i]);
Serial.println();
Serial.println("*********");
}
}
};
void setup()
{
Serial.begin(115200);
// Create the BLE Device
BLEDevice::init("UART Service");
// 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);
pTxCharacteristic->addDescriptor(new BLE2902());
BLECharacteristic *pRxCharacteristic = pService->createCharacteristic(
CHARACTERISTIC_UUID_RX,
BLECharacteristic::PROPERTY_WRITE);
pRxCharacteristic->setCallbacks(new MyCallbacks());
// Start the service
pService->start();
// Start advertising
pServer->getAdvertising()->start();
Serial.println("Waiting a client connection to notify...");
}
void loop()
{
if (deviceConnected)
{
// ============================================
// First write might fail because client has not yet enabled notifications
// ============================================
pTxCharacteristic->setValue(&txValue, 1);
pTxCharacteristic->notify();
txValue++;
delay(10); // bluetooth stack will go into congestion, if too many packets are sent
}
// 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;
}
}```
### Debug Messages:No crash, just missing a callback