Overview
Bluetooth standard offers basic rate (BR) or enhanced data rate (EDR) and Bluetooth Low Energy (LE) support. Devices that can support BR/EDR and Bluetooth LE are referred to as dual-mode devices. Typically, in a Bluetooth system, a mobile phone or laptop computer acts as a dual-mode device.
Devices that only support Bluetooth LE are referred to as single-mode devices where the low power consumption is the primary concern for application development, such as those that run on coin cell batteries.
This article focus on:
- Detailed description of the BR/EDR profiles.
- Bluetooth LE profiles.
1.1 Bluetooth protocol stack
The Bluetooth protocol stack consists of two sections, the controller and the host, derived from the original Bluetooth core specification where the two sections were often implemented separately.
1.1.1 BR/EDR protocol stack
The BR/EDR protocol stack architecture is illustrated in Figure 1.
The controller section includes the Physical Layer (PHY), Link Layer (LL) and Host-Controller Interface (HCI).
- 1) The physical layer (PHY) is the lowest layer of the Bluetooth protocol stack to manage physical channels and links.
- 2) The link layer (LL) is used to control the radio link between two devices, handling matters such as link establishment, querying device abilities and providing power control.
- 3)The host control interface (HCI) provides a means of communication between the host and controller using a standardized interface.
The host includes various communication protocols, as described below.
- 1) The logical link control and adaption protocol (L2CAP) provides data encapsulation services to the upper layers that enable logical end-to-end data communication.
- 2) The radio frequency communication (RFCOMM) is a set of transport protocols on top of the L2CAP protocol, providing emulated RS-232 serial ports.
- 3) The generic access profile (GAP) defines the generic procedures related to discovery of Bluetooth devices and link management aspects of connecting to Bluetooth devices.
- 4) The service discovery protocol (SDP) is used to allow devices to discover the supported services, and parameters to use to connect to them.
- 5) The hands-free profile (HFP) allows hands-free kits to control the mobile phone of calling functions and provide the voice connection between devices.
- 6) The object exchange (OBEX) is a communications protocol that facilitates the exchange of binary objects between devices.
- 7) The phonebook access profile (PBAP) defines the procedures and protocols to exchange phonebook objects between devices.
- 8) The Advanced Audio Distribution Profile (A2DP) defines how multimedia audio is streamed from one device to another via Bluetooth connection
- 9) The audio/video distribution transport protocol (AVDTP) is used by the advanced audio distribution profile to stream music to stereo headsets over the L2CAP channel intended for video distribution profile in the Bluetooth transmission.
- 10) The audio/video control transport protocol (AVCTP) is used to transport the command/response messages exchanged for the control of distant A/V devices over point-to-point connections.
- 11) The audio/video remote control profile (AVRCP) defines the features and procedures required in order to ensure interoperability between Bluetooth devices with audio/video control functions in the audio/video distribution scenarios.
- 12) The serial port profile (SPP) emulates a serial cable to provide a simple substitute for existing RS-232.
1.1.2 Bluetooth LE protocol stack
The Bluetooth LE protocol stack architecture is shown in Figure 2.
附录
RK3308蓝牙使用
系统概况：
# uname -a Linux rockchip 4.4.143 #9 SMP PREEMPT Wed Feb 13 18:38:41 CST 2019 armv7l GNU/Linux 蓝牙芯片：AP6212
1、查看电源是否开启
# cd /sys/class/rfkill # ls rfkill0 rfkill1 rfkill2 # rfkill <--- 查看蓝牙对应的目录 ID TYPE DEVICE SOFT HARD 0 bluetooth bt_default blocked unblocked 1 wlan phy0 unblocked unblocked 2 wlan brcmfmac-wifi unblocked unblocked # cd rfkill0/ # cat state <--- 查看电源状态 0 <--- power down # echo 1 > ./state <--- power up [ 423.917629] [BT_RFKILL]: rfkill_rk_set_power: set bt wake_host pin output high! [ 423.980538] [BT_RFKILL]: rfkill_rk_set_power: set bt wake_host pin input! [ 423.980608] [BT_RFKILL]: ENABLE UART_RTS [ 424.081438] [BT_RFKILL]: DISABLE UART_RTS [ 424.081539] [BT_RFKILL]: bt turn on power
2、查看蓝牙是否启动
# hciconfig -a <--- 蓝牙设备未启动 # brcm_patchram_plus1 --bd_addr_rand --enable_hci --no2bytes --use_baudrate_for_download --tosleep 200000 --baudrate 1500000 --patchram /system/etc/firmware/bcm43438a1.hcd /dev/ttyS4 & <--- 启动蓝牙设备 # hciconfig -a hci0: Type: Primary Bus: UART BD Address: 90:1B:07:8D:34:B0 ACL MTU: 1021:8 SCO MTU: 64:1 DOWN <--- 蓝牙Down状态 RX bytes:612 acl:0 sco:0 events:30 errors:0 TX bytes:398 acl:0 sco:0 commands:30 errors:0 Features: 0xbf 0xfe 0xcf 0xfe 0xdb 0xff 0x7b 0x87 Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3 Link policy: RSWITCH SNIFF Link mode: SLAVE ACCEPT
3、激活蓝牙
# hciconfig hci0 up # hciconfig dev hci0: Type: Primary Bus: UART BD Address: 90:1B:07:8D:34:B0 ACL MTU: 1021:8 SCO MTU: 64:1 UP RUNNING RX bytes:1224 acl:0 sco:0 events:60 errors:0 TX bytes:796 acl:0 sco:0 commands:60 errors:0 # hciconfig -a <--- 查看详细信息 hci0: Type: Primary Bus: UART BD Address: 90:1B:07:8D:34:B0 ACL MTU: 1021:8 SCO MTU: 64:1 UP RUNNING RX bytes:1224 acl:0 sco:0 events:60 errors:0 TX bytes:796 acl:0 sco:0 commands:60 errors:0 Features: 0xbf 0xfe 0xcf 0xfe 0xdb 0xff 0x7b 0x87 Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3 Link policy: RSWITCH SNIFF Link mode: SLAVE ACCEPT Name: 'BCM43438A1 26MHz AP6212A1_CL1 BT4.0 OTP-BD-0058' Class: 0x000000 Service Classes: Unspecified Device Class: Miscellaneous, HCI Version: 4.0 (0x6) Revision: 0xf9 LMP Version: 4.0 (0x6) Subversion: 0x2209 Manufacturer: Broadcom Corporation (15)
4、扫描看下
# hcitool scan Scanning ... 00:1A:7D:DA:71:13 CHENTONG1070 70:BB:E9:C7:1B:1C 小米手机 94:87:E0:B4:09:82 小米手机8 50:3C:EA:AF:D7:00 OPPO R11s 20:47:DA:BE:3B:B3 小米手机6 28:B2:BD:CA:69:BB GUOZF668 20:18:06:25:62:79 HC-05 34:D7:12:91:DC:C0 坚果 Pro 2 特别版
参考资料：