零. 概述
本文章主要講下藍牙設備類型class of device的概念，service class ,major device,minor device類型以及舉例說明下某一個cod的解析。html
一. 聲明
本專欄文章咱們會以連載的方式持續更新，本專欄計劃更新內容以下：android
第一篇:藍牙綜合介紹 ，主要介紹藍牙的一些概念，產生背景，發展軌跡，市面藍牙介紹，以及藍牙開發板介紹。git
第二篇:Transport層介紹,主要介紹藍牙協議棧跟藍牙芯片以前的硬件傳輸協議,好比基於UART的H4,H5,BCSP，基於USB的H2等github
第三篇:傳統藍牙controller介紹，主要介紹傳統藍牙芯片的介紹，包括射頻層（RF），基帶層（baseband），鏈路管理層（LMP）等shell
第四篇:傳統藍牙host介紹，主要介紹傳統藍牙的協議棧，好比HCI,L2CAP,SDP,RFCOMM,HFP,SPP,HID,AVDTP,AVCTP,A2DP,AVRCP,OBEX,PBAP,MAP等等一系列的協議吧。app
第五篇：低功耗藍牙controller介紹，主要介紹低功耗藍牙芯片，包括物理層（PHY），鏈路層（LL）less
第六篇：低功耗藍牙host介紹，低功耗藍牙協議棧的介紹，包括HCI,L2CAP,ATT,GATT,SM等ide
第七篇：藍牙芯片介紹，主要介紹一些藍牙芯片的初始化流程，基於HCI vendor command的擴展oop
第八篇：附錄，主要介紹以上經常使用名詞的介紹以及一些特殊流程的介紹等。學習
另外，開發板以下所示，對於想學習藍牙協議棧的最好人手一套。以便更好的學習藍牙協議棧，相信我，學完這一套視頻你將擁有修改任何協議棧的能力（好比Linux下的bluez，Android下的bluedroid）。
-------------------------------------------------------------------------------------------------------------------------
CSDN學院連接（進入選擇你想要學習的課程）：https://edu.csdn.net/lecturer/5352?spm=1002.2001.3001.4144
藍牙交流扣扣羣：970324688
Github代碼：https://github.com/sj15712795029/bluetooth_stack
入手開發板：https://item.taobao.com/item.htm?spm=a1z10.1-c-s.w4004-22329603896.18.5aeb41f973iStr&id=622836061708
藍牙學習目錄：http://www.javashuo.com/article/p-cydcgesb-nt.html
--------------------------------------------------------------------------------------------------------------------------
二.藍牙設備類型Cod（class of device）概念
cod就是設備類型（class of device），設備在藍牙初始化的時候就要聲明本身的設備類型，對方inquiry的時候會掃描到你的設備類型，並作對應的顯示，典型的應用如android手機的搜索前面顯示的小圖標，如圖前面的這排圖標都是根據cod來顯示的。
另外，須要注意的是，協議必定要跟cod匹配，好比你想作一個藍牙鍵盤，不能註冊audio的cod，不然頗有可能出現奇奇怪怪的問題，此部分尤爲注意。
Cod參照文章: https://www.bluetooth.com/specifications/assigned-numbers/baseband/
三.Cod結構以及子項
Cod的結構如上圖，一共有3個byte，其中一共分爲4個部分
3.1 Service class:設備類型
| Bit No. | Major Service Class |
|---|---|
| 13 | Limited Discoverable Mode [Ref #1] |
| 14 | (reserved) |
| 15 | (reserved) |
| 16 | Positioning (Location identification) |
| 17 | Networking (LAN, Ad hoc, …) |
| 18 | Rendering (Printing, Speakers, …) |
| 19 | Capturing (Scanner, Microphone, …) |
| 20 | Object Transfer (v-Inbox, v-Folder, …) |
| 21 | Audio (Speaker, Microphone, Headset service, …) |
| 22 | Telephony (Cordless telephony, Modem, Headset service, …) |
| 23 | Information (WEB-server, WAP-server, …) |
3.2 Major device class主要是設備的主要類型
有以下幾種值：
| 12 | 11 | 10 | 9 | 8 | Major Device Class |
|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | Miscellaneous [Ref #2] |
| 0 | 0 | 0 | 0 | 1 | Computer (desktop, notebook, PDA, organizer, … ) |
| 0 | 0 | 0 | 1 | 0 | Phone (cellular, cordless, pay phone, modem, …) |
| 0 | 0 | 0 | 1 | 1 | LAN /Network Access point |
| 0 | 0 | 1 | 0 | 0 | Audio/Video (headset, speaker, stereo, video display, VCR, … |
| 0 | 0 | 1 | 0 | 1 | Peripheral (mouse, joystick, keyboard, … ) |
| 0 | 0 | 1 | 1 | 0 | Imaging (printer, scanner, camera, display, …) |
| 0 | 0 | 1 | 1 | 1 | Wearable |
| 0 | 1 | 0 | 0 | 0 | Toy |
| 0 | 1 | 0 | 0 | 1 | Health |
| 1 | 1 | 1 | 1 | 1 | Uncategorized: device code not specified |
| X | X | X | X | X | All other values reserved |
3.3 Minor device class是對應於每種major下面的子類
如如下
Minor Device Class field – Computer Major Class
| 7 | 6 | 5 | 4 | 3 | 2 | Minor Device Class bit no. of CoD |
|---|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | 0 | Uncategorized, code for device not assigned |
| 0 | 0 | 0 | 0 | 0 | 1 | Desktop workstation |
| 0 | 0 | 0 | 0 | 1 | 0 | Server-class computer |
| 0 | 0 | 0 | 0 | 1 | 1 | Laptop |
| 0 | 0 | 0 | 1 | 0 | 0 | Handheld PC/PDA (clamshell) |
| 0 | 0 | 0 | 1 | 0 | 1 | Palm-size PC/PDA |
| 0 | 0 | 0 | 1 | 1 | 0 | Wearable computer (watch size) |
| 0 | 0 | 0 | 1 | 1 | 1 | Tablet |
| X | X | X | X | X | X | All other values reserved |
Minor Device Class field – Phone Major Class
| 7 | 6 | 5 | 4 | 3 | 2 | Minor Device Class bit no. of CoD |
|---|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | 0 | Uncategorized, code for device not assigned |
| 0 | 0 | 0 | 0 | 0 | 1 | Cellular |
| 0 | 0 | 0 | 0 | 1 | 0 | Cordless |
| 0 | 0 | 0 | 0 | 1 | 1 | Smartphone |
| 0 | 0 | 0 | 1 | 0 | 0 | Wired modem or voice gateway |
| 0 | 0 | 0 | 1 | 0 | 1 | Common ISDN access |
| X | X | X | X | X | X | All other values reserved |
Minor Device Class field – LAN/Network Access Point Major Class
| 7 | 6 | 5 | Minor Device Class bit no. of CoD |
|---|---|---|---|
| 0 | 0 | 0 | Fully available |
| 0 | 0 | 1 | 1% to 17% utilized |
| 0 | 1 | 0 | 17% to 33% utilized |
| 0 | 1 | 1 | 33% to 50% utilized |
| 1 | 0 | 0 | 50% to 67% utilized |
| 1 | 0 | 1 | 67% to 83% utilized |
| 1 | 1 | 0 | 83% to 99% utilized |
| 1 | 1 | 1 | No service available |
| X | X | X | All other values reserved |
Table 6: The LAN/Network Access Point Load Factor field
The exact loading formula is not standardized. It is up to each LAN/Network Access Point implementation to determine what internal conditions to report as a utilization percentage. The only requirement is for the number to reflect an ever-increasing utilization of communication resources within the box. As a recommendation: a client locating multiple LAN/Network Access Points should attempt to connect to the one reporting the lowest load.
| 4 | 3 | 2 | Minor Device Class bit no. of CoD |
|---|---|---|---|
| 0 | 0 | 0 | Uncategorized (use this value if no others apply) |
| X | X | X | All other values reserved |
Table 7: Reserved sub-field for the LAN/Network Access Point
Minor Device Class field – Audio/Video Major Class
| 7 | 6 | 5 | 4 | 3 | 2 | Minor Device Class bit no. of CoD |
|---|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | 0 | Uncategorized, code not assigned |
| 0 | 0 | 0 | 0 | 0 | 1 | Wearable Headset Device |
| 0 | 0 | 0 | 0 | 1 | 0 | Hands-free Device |
| 0 | 0 | 0 | 0 | 1 | 1 | (Reserved) |
| 0 | 0 | 0 | 1 | 0 | 0 | Microphone |
| 0 | 0 | 0 | 1 | 0 | 1 | Loudspeaker |
| 0 | 0 | 0 | 1 | 1 | 0 | Headphones |
| 0 | 0 | 0 | 1 | 1 | 1 | Portable Audio |
| 0 | 0 | 1 | 0 | 0 | 0 | Car audio |
| 0 | 0 | 1 | 0 | 0 | 1 | Set-top box |
| 0 | 0 | 1 | 0 | 1 | 0 | HiFi Audio Device |
| 0 | 0 | 1 | 0 | 1 | 1 | VCR |
| 0 | 0 | 1 | 1 | 0 | 0 | Video Camera |
| 0 | 0 | 1 | 1 | 0 | 1 | Camcorder |
| 0 | 0 | 1 | 1 | 1 | 0 | Video Monitor |
| 0 | 0 | 1 | 1 | 1 | 1 | Video Display and Loudspeaker |
| 0 | 1 | 0 | 0 | 0 | 0 | Video Conferencing |
| 0 | 1 | 0 | 0 | 0 | 1 | (Reserved) |
| 0 | 1 | 0 | 0 | 1 | 0 | Gaming/Toy |
| X | X | X | X | X | X | All other values reserved |
Minor Device Class field – Peripheral Major Class
| 7 | 6 | Minor Device Class bit no. of CoD |
|---|---|---|
| 0 | 0 | Not Keyboard / Not Pointing Device |
| 0 | 1 | Keyboard |
| 1 | 0 | Pointing device |
| 1 | 1 | Combo keyboard/pointing device |
Table 9: The Peripheral Major Class keyboard/pointing device field
Bits six and seven independently specify mouse, keyboard or combo mouse/keyboard devices. These may be combined with the lower bits in a multifunctional device.
| 5 | 4 | 3 | 2 | Minor Device Class bit no. of CoD |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | Uncategorized device |
| 0 | 0 | 0 | 1 | Joystick |
| 0 | 0 | 1 | 0 | Gamepad |
| 0 | 0 | 1 | 1 | Remote control |
| 0 | 1 | 0 | 0 | Sensing device |
| 0 | 1 | 0 | 1 | Digitizer tablet |
| 0 | 1 | 1 | 0 | Card Reader (e.g. SIM Card Reader) |
| 0 | 1 | 1 | 1 | Digital Pen |
| 1 | 0 | 0 | 0 | Handheld scanner for bar-codes, RFID, etc. |
| 1 | 0 | 0 | 1 | Handheld gestural input device (e.g., 「wand」 form factor) |
| X | X | X | X | All other values reserved |
Minor Device Class field – Imaging Major Class
| 7 | 6 | 5 | 4 | Minor Device Class bit no. of CoD |
|---|---|---|---|---|
| X | X | X | 1 | Display |
| X | X | 1 | X | Camera |
| X | 1 | X | X | Scanner |
| 1 | X | X | X | Printer |
| X | X | X | X | All other values reserved |
Table 11: The Imaging Major Class bits four to seven
Bits four to seven independently specify display, camera, scanner or printer. These may be combined in a multifunctional device.
| 3 | 2 | Minor Device Class bit no. of CoD |
|---|---|---|
| 0 | 0 | Uncategorized, default |
| X | X | All other values reserved |
Minor Device Class field – Wearable Major Class
The Minor Class segment is the lowest level of granularity for defining a Bluetooth Device. There are 64 different possible minor classes.
| 7 | 6 | 5 | 4 | 3 | 2 | Minor Device Class bit no. of CoD |
|---|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | 1 | Wristwatch |
| 0 | 0 | 0 | 0 | 1 | 0 | Pager |
| 0 | 0 | 0 | 0 | 1 | 1 | Jacket |
| 0 | 0 | 0 | 1 | 0 | 0 | Helmet |
| 0 | 0 | 0 | 1 | 0 | 1 | Glasses |
| X | X | X | X | X | X | All other values reserved |
Minor Device Class field – Toy Major Class
| 7 | 6 | 5 | 4 | 3 | 2 | Minor Device Class bit no. of CoD |
|---|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | 1 | Robot |
| 0 | 0 | 0 | 0 | 1 | 0 | Vehicle |
| 0 | 0 | 0 | 0 | 1 | 1 | Doll / Action figure |
| 0 | 0 | 0 | 1 | 0 | 0 | Controller |
| 0 | 0 | 0 | 1 | 0 | 1 | Game |
| X | X | X | X | X | X | All other values reserved |
Minor Device Class field – Health
| 7 | 6 | 5 | 4 | 3 | 2 | Minor Device Class bit no. of CoD |
|---|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | 0 | Undefined |
| 0 | 0 | 0 | 0 | 0 | 1 | Blood Pressure Monitor |
| 0 | 0 | 0 | 0 | 1 | 0 | Thermometer |
| 0 | 0 | 0 | 0 | 1 | 1 | Weighing Scale |
| 0 | 0 | 0 | 1 | 0 | 0 | Glucose Meter |
| 0 | 0 | 0 | 1 | 0 | 1 | Pulse Oximeter |
| 0 | 0 | 0 | 1 | 1 | 0 | Heart/Pulse Rate Monitor |
| 0 | 0 | 0 | 1 | 1 | 1 | Health Data Display |
| 0 | 0 | 1 | 0 | 0 | 0 | Step Counter |
| 0 | 0 | 1 | 0 | 0 | 1 | Body Composition Analyzer |
| 0 | 0 | 1 | 0 | 1 | 0 | Peak Flow Monitor |
| 0 | 0 | 1 | 0 | 1 | 1 | Medication Monitor |
| 0 | 0 | 1 | 1 | 0 | 0 | Knee Prosthesis |
| 0 | 0 | 1 | 1 | 0 | 1 | Ankle Prosthesis |
| 0 | 0 | 1 | 1 | 1 | 0 | Generic Health Manager |
| 0 | 0 | 1 | 1 | 1 | 1 | Personal Mobility Device |
| X | X | X | X | X | X | All other values reserved |
Type:通常是00用於後11bit service class作掩碼用
四.舉例分析一個藍牙設備的cod
下面咱們來舉幾個例子來講明下（在舉例子以前推薦一個文章能夠生成cod）
http://bluetooth-pentest.narod.ru/software/bluetooth_class_of_device-service_generator.html
拿一個0x340404來講明下
0x340404=001101000000010000000100b
Service class = 00110100000
對應的是
Major device class = 00100 ,以下圖
而後minor device class=000001b,而後咱們找到Audio/Video的minor device class對應以下
咱們來看個btsnoop對應下看看咱們分析的對不對
咱們也來用我上面給的鏈接生成下看看是否跟咱們同樣，來加深下印象