BLE Heart Rate Monitor

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Overview

• WHOOP (Broadcast Heart Rate mode)
• Polar sensors (H10 chest strap, OH1 / Verity Sense optical arm bands)
• Wahoo TICKR, TICKR X
• Garmin HRM-Pro, HRM-Dual
• Gym equipment with BLE HR broadcast
• Any device implementing the standard BLE Heart Rate Profile (0x180D)

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How It Works

Phone (iOS/Android)
    │
    │── BLE Scan (filter: 0x180D service)
    │
    ▼
BLE Heart Rate Monitor
    │
    │── Subscribe to HR Measurement (0x2A37)
    │
    ▼
Real-time HR samples → HeartRateSample stream
    │
    │── bpm, rr_intervals_ms, device_id, timestamp
    │
    ▼
Your App

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Platform Setup

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iOS

<key>NSBluetoothAlwaysUsageDescription</key>
<string>This app uses Bluetooth to connect to heart rate monitors.</string>

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Android

<uses-permission android:name="android.permission.BLUETOOTH_SCAN"
    android:usesPermissionFlags="neverForLocation" />
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />

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Usage

import 'package:synheart_wear/synheart_wear.dart';

final bleHrm = BleHrmProvider();

// Scan for nearby HR monitors
final devices = await bleHrm.scan(
  timeoutMs: 10000,
  namePrefix: 'WHOOP',  // optional filter
);

// Connect to a device
await bleHrm.connect(
  deviceId: devices.first.deviceId,
  sessionId: 'my-session',  // optional
);

// Listen to heart rate samples
bleHrm.onHeartRate.listen((sample) {
  print('BPM: ${sample.bpm}');
  if (sample.rrIntervalsMs != null) {
    print('RR: ${sample.rrIntervalsMs}');
  }
});

// Disconnect when done
await bleHrm.disconnect();

import SynheartWear

let config = SynheartWearConfig(enabledAdapters: [.bleHrm])
let synheartWear = SynheartWear(config: config)

guard let bleHrm = synheartWear.bleHrm else { return }

// Scan
let devices = try await bleHrm.scan(timeoutMs: 10000, namePrefix: "WHOOP")

// Connect
try await bleHrm.connect(deviceId: devices.first.deviceId)

// Stream
for await sample in bleHrm.onHeartRate {
    print("BPM: \(sample.bpm)")
}

// Disconnect
try await bleHrm.disconnect()

import ai.synheart.wear.SynheartWear
import ai.synheart.wear.models.DeviceAdapter

val synheartWear = SynheartWear(
    context = this,
    config = SynheartWearConfig(
        enabledAdapters = setOf(DeviceAdapter.BLE_HRM)
    )
)

val bleHrm = synheartWear.bleHrm ?: return

// Scan
val devices = bleHrm.scan(timeoutMs = 10000, namePrefix = "WHOOP")

// Connect
bleHrm.connect(deviceId = devices.first().deviceId)

// Collect
bleHrm.heartRateFlow.collect { sample ->
    Log.d(TAG, "BPM: ${sample.bpm}")
}

// Disconnect
bleHrm.disconnect()

​

API Reference

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Methods

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BleHrmDevice

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HeartRateSample

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Error Codes

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WHOOP Broadcast Setup

1. Open the WHOOP app on your phone
2. Go to Device Settings (tap your WHOOP device)
3. Enable Broadcast Heart Rate
4. Your WHOOP will now appear in BLE scans as a standard HR monitor

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Reconnection

• 3 retry attempts with exponential backoff (1s, 2s, 4s)
• After retries are exhausted, a DISCONNECTED error is emitted on the stream
• Your app can then prompt the user to reconnect

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Limitations

• Single device: Only one BLE HRM device can be connected at a time (v1)
• Phone-side only: Requires the phone to be in BLE range of the HR monitor
• No HRV calculation: Raw RR intervals are provided when available, but HRV calculation is not performed by the provider
• Battery dependent: Battery level monitoring is optional (enableBattery: true during connect)

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Architecture