startNotifications gives empty values

[Krupskis]

I am printing value, but getting empty objects there. It seems I am getting an error The attribute could not be found for some reason. Any help would be appreciated. I double checked the UUIDs, I made sure to send buffers of size way below mtu, currently at 20 bytes. From what I understand TO JS log are actual values I am getting from the ble channel, but I am not getting that value on my callback.

Output from XCode

⚡️  To Native ->  BluetoothLe startNotifications 10637181
⚡️  BluetoothLe - Set notifications true
⚡️  BluetoothLe - Reject setNotifications|4FAFC201-1FB5-459E-8FCC-C5C9C331914B|BEB5483E-36E1-4688-B7F5-EA07361B26A8 The attribute could not be found.
ERROR MESSAGE:  {"errorMessage":"The attribute could not be found.","message":"The attribute could not be found."}
⚡️  [error] - {"errorMessage":"The attribute could not be found.","message":"The attribute could not be found."}
⚡️  TO JS {"value":"01 00 00 00 00 80 13 f1 01 00 00 00 00 00 0d f1 01 00 00 00 "}
⚡️  TO JS {"value":"00 00 10 f1 01 00 00 00 00 80 1d f1 01 00 00 00 00 00 2d f1 "}
⚡️  TO JS {"value":"01 00 00 00 00 80 31 f1 01 00 00 00 00 80 2f f1 01 00 00 00 "}
⚡️  TO JS {"value":"00 00 19 f1 01 00 00 00 00 80 16 f1 01 00 00 00 00 80 11 f1 "}
⚡️  TO JS {"value":"01 00 00 00 00 00 10 f1 01 00 00 00 00 00 12 f1 01 00 00 00 "}
⚡️  TO JS {"value":"00 00 0d f1 01 00 00 00 00 00 00 f1 01 00 00 00 00 00 f3 f0 "}
⚡️  [log] - received value {}

This is my bluetooth code on capacitor:

const connect = async (deviceId: string) => {
    const device = await BleClient.requestDevice({
      services: ["4fafc201-1fb5-459e-8fcc-c5c9c331914b"],
    });
    await BleClient.connect(device.deviceId);

    return device.deviceId;
  };

const deviceId = await connect(device.device.deviceId);
                // let buffer: ArrayBuffer = new ArrayBuffer(441000 * 4);
                // const combinedView = new DataView(buffer);
                let buffer = new Uint8Array((32 * 441000 - 512) / 4);
                console.log("mtu", BleClient.getMtu(deviceId));

                const result = await BleClient.startNotifications(
                  deviceId,
                  "4fafc201-1fb5-459e-8fcc-c5c9c331914b",
                  "beb5483e-36e1-4688-b7f5-ea07361b26a8",
                  (value) => {
                    console.log("received value", value);
                    console.log("current heart rate", parseHeartRate(value));
                  }
                );

This is my bluetooth code on esp32:

#include "Server.h"
#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEServer.h>
#include <Arduino.h>

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

static bool s_is_connected = false;


class ServerHandler: public BLEServerCallbacks {
    void onConnect(BLEServer* pServer) {
        s_is_connected = true;
        Serial.println("Connected");
    }

    void onDisconnect(BLEServer* pServer) {
        s_is_connected = false;
        Serial.println("Disconnected");
        BLEDevice::startAdvertising();
    }
};

BluetoothServer::BluetoothServer() {}

void BluetoothServer::startAdvertising()
{

    Serial.println("Starting BLE Server");
    BLEDevice::init("ESP32");
    BLEDevice::setMTU(182);
    pServer = BLEDevice::createServer();
    pServer->setCallbacks(new ServerHandler());
    pService = pServer->createService(SERVICE_UUID);
    audioCharacteristic = pService->createCharacteristic(
        CHARACTERISTIC_UUID,
        BLECharacteristic::PROPERTY_READ |
            BLECharacteristic::PROPERTY_WRITE | BLECharacteristic::PROPERTY_NOTIFY);
    


    audioCharacteristic->setValue("ESP32Hello World says ESP32Hello World");
    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);
    pAdvertising->setMinPreferred(0x12);
    pAdvertising->setMinInterval(0x20);
    pAdvertising->setMaxInterval(0x40);
    BLEDevice::startAdvertising();
    Serial.printf("MTU size: %d bytes\n", BLEDevice::getMTU());
}

void BluetoothServer::setValue(uint8_t *value, size_t len)
{
    if (!s_is_connected) {
        delay(50); // Wait for a connection
        return;
    }
    
    audioCharacteristic->setValue(value, len);
    audioCharacteristic->notify();
    Serial.println("Sent some data");
    delay(4);
}

[pwespi]

Your characteristic in the esp32 code might be missing a descriptor.