树莓派3B+连接蓝牙设备

参考：
http://shumeipai.nxez.com/2016/07/10/raspberry-pi-3-how-to-use-bluetooth.html
https://blog.csdn.net/guzhong10/article/details/78574577
一、连接蓝牙音箱

1. 升级安装蓝牙相关软件包
   sudo apt-get update
   sudo apt-get upgrade -y
   sudo apt-get dist-upgrade -y
   sudo apt-get install pi-bluetooth bluez bluez-firmware blueman

2. 添加pi用户到蓝牙组
   sudo usermod -G bluetooth -a pi

3. 重启
   sudo reboot

4. 使用命令打开蓝牙
   pi@raspberrypi:/ $ sudo bluetoothctl
   [bluetooth]#list
   Controller B8:27:EB:3D:15:E9 raspberrypi [default]
   [bluetooth]# scan on
   Discovery started
   [CHG] Device 5F:FC:4E:B0:EA:59 RSSI: -97
   [NEW] Device 42:29:9A:3B:75:E6 42-29-9A-3B-75-E6
   [bluetooth]# devices
   Device 30:21:4F:54:4D:8E Newmine
   Device 72:D7:02:62:CE:A0 72-D7-02-62-CE-A0
   Device 5F:FC:4E:B0:EA:59 5F-FC-4E-B0-EA-59
   Device E4:A7:C5:C8:55:F5 HUAWEI Mate 10 Pro
   Device 42:29:9A:3B:75:E6 42-29-9A-3B-75-E6
   [bluetooth]# pair 30:21:4F:54:4D:8E
   Attempting to pair with 30:21:4F:54:4D:8E
   Failed to pair: org.bluez.Error.AlreadyExists(已配对成功过，如果是初次配对是显示成功的信息）
   [bluetooth]# trust 30:21:4F:54:4D:8E
   Changing 30:21:4F:54:4D:8E trust succeeded
   [bluetooth]# connect 30:21:4F:54:4D:8E
   Attempting to connect to 30:21:4F:54:4D:8E
   [CHG] Device 30:21:4F:54:4D:8E Connected: yes
   Connection successful
   [CHG] Device 5F:FC:4E:B0:EA:59 RSSI: -86
   [CHG] Device 30:21:4F:54:4D:8E ServicesResolved: yes
   [Newmine]#quit

疑问：
与手机mate10 Pro可以配对成功，但是无法连接成功。在手机的蓝牙设置菜单中，显示raspberrypi为已配对的设备，但是点击连接无反应。
[bluetooth]# trust E4:A7:C5:C8:55:F5
Changing E4:A7:C5:C8:55:F5 trust succeeded
[CHG] Device 5F:FC:4E:B0:EA:59 RSSI: -96
[bluetooth]# connect E4:A7:C5:C8:55:F5
Attempting to connect to E4:A7:C5:C8:55:F5
Failed to connect: org.bluez.Error.Failed