1. 定义常量

NSString * const HeartRateServiceUUIDString = @"180D";
NSString * const HeartRateCharacteristicUUIDStringNoti  =  @"2A37";
NSString * const RealTimeHeartRateNotifaction = @"RealTimeHeartRateNotifaction";

2.在扫描到的外设中找心率服务

- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error {
    if (error) {
        
        NSLog(@"查找服务失败");
    }
    //find HR service
    if ([service.UUID.UUIDString isEqualToString: HeartRateServiceUUIDString]) {
        for (CBCharacteristic *characteristic in  service.characteristics)  {
            if ([characteristic.UUID.UUIDString isEqualToString: HeartRateCharacteristicUUIDStringNoti]) {
                [peripheral setNotifyValue:YES forCharacteristic:characteristic];
                self.characteristicHR = characteristic;
            }
        }
    }
  }

3.在外设收到通知回调代理方法里面获取心率值

- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error {
    [self removeTimer];
    
    if ([characteristic.UUID.UUIDString isEqualToString: HeartRateCharacteristicUUIDStringNoti]) {
        
        Byte *bytes = (Byte *)characteristic.value.bytes;
        int hr = bytes[1];
        //post notification update UI
        [[NSNotificationCenter defaultCenter] postNotificationName: RealTimeHeartRateNotifaction object:nil userInfo:@{@"realTimeHR":@(hr)}];
        return;
    }
}

4.监听通知,更新UI

 [[NSNotificationCenterdefaultCenter] addObserver:selfselector:@selector(realTimeHR:) name:APPSRealTimeHRNotiobject:nil];

//updateHR
- (void)realTimeHR:(NSNotification *)nofi{
    Log(@"%@",nofi.userInfo);
    int hr = [nofi.userInfo[@"realTimeHR"] intValue];
    
    [heartRateCircle setProgress:hr*1.0/180  animated:YES];
    lblheartRate2.text=[NSString stringWithFormat:@"%d",hr];
}