DA1458x BASS Database的组成结构 -- Battery Service 分析（一）

Overview

本文基于DA1458x SDK 5.0.4。
Battery Service 以下简称BAS or BASS。BASS的代码主要有以下两个组C文件组成
BASS
另，BASS是依赖于APP_TASK任务来调度管理的。具体框架如下图（摘自Dialog官方文档）
DA1458X_SDK_ARCH

Full BAS Database Description （BAS Database 分析）

BASS的Database的变量名为 bas_att_db,由以下5个成员组成

No.	Name	Description
1	BAS_IDX_SVC	Battery Service Declaration
2	BAS_IDX_BATT_LVL_CHAR	Battery Level Characteristic Declaration
3	BAS_IDX_BATT_LVL_VAL	Battery Level Characteristic Value
4	BAS_IDX_BATT_LVL_NTF_CFG	Battery Level Characteristic - Client Characteristic Configuration Descriptor
5	BAS_IDX_BATT_LVL_PRES_FMT	Battery Level Characteristic - Characteristic Presentation Format Descriptor

这个变量非常重要，本文我们就围绕着它来一步步来分析。

bas_att_db结构体数组索引

首先这是一个结构体数组的索引，该索引采取的是枚举类型，方便阅读和理解。

/// Battery Service Attributes Indexes
enum
{
    BAS_IDX_SVC,

    BAS_IDX_BATT_LVL_CHAR,
    BAS_IDX_BATT_LVL_VAL,
    BAS_IDX_BATT_LVL_NTF_CFG,
    BAS_IDX_BATT_LVL_PRES_FMT,

    BAS_IDX_NB,
};

接下来我们看下attm_desc这个结构体的定义

struct attm_desc 结构体的定义

这个结构体的定义如下

 /// Attribute description (used to create database)
 struct attm_desc
 {
     /// Element UUID
     uint16_t uuid;
     /// Attribute permission
     uint16_t perm;
     /// Maximum length of the element
     att_size_t max_length;
     /// Current length of the element
     att_size_t length;
     /// Element value array
     uint8_t* value;
 };

我们可以看到，第一个成员是16位UUID，用来记录这个Attribute（属性）的UUID；
第二个成员是Attribute permission（属性权限）；
第三个成员是Maximum length of the element（元素的最大长度）；
第四个成员是Current length of the element（当前元素的长处）；
第五个成员是Element Value array（元素数组）。

uuid和perm为16bit无符号整型变量，value为uint8_t数组指针，att_size_t类型其实uint16_t

/// Attribute length type
typedef uint16_t att_size_t;

bas_att_db定义

定义如下（bass.c文件中）

/*
 * BAS ATTRIBUTES DEFINITION
 ****************************************************************************************
 */

/// Full BAS Database Description - Used to add attributes into the database
const struct attm_desc bas_att_db[BAS_IDX_NB] =
{
    // Battery Service Declaration
    [BAS_IDX_SVC]                  =   {ATT_DECL_PRIMARY_SERVICE, PERM(RD, ENABLE), sizeof(bas_svc),
                                        sizeof(bas_svc), (uint8_t *)&bas_svc},

    // Battery Level Characteristic Declaration
    [BAS_IDX_BATT_LVL_CHAR]        =   {ATT_DECL_CHARACTERISTIC, PERM(RD, ENABLE), sizeof(bas_batt_level_char),
                                        sizeof(bas_batt_level_char), (uint8_t *)&bas_batt_level_char},
    // Battery Level Characteristic Value
    [BAS_IDX_BATT_LVL_VAL]         =   {ATT_CHAR_BATTERY_LEVEL, PERM(RD, ENABLE), sizeof(uint8_t),
                                        0, NULL},
    // Battery Level Characteristic - Client Characteristic Configuration Descriptor
    [BAS_IDX_BATT_LVL_NTF_CFG]     =   {ATT_DESC_CLIENT_CHAR_CFG, PERM(RD, ENABLE)|PERM(WR, ENABLE), sizeof(uint16_t),
                                        0, NULL},
    // Battery Level Characteristic - Characteristic Presentation Format Descriptor
    [BAS_IDX_BATT_LVL_PRES_FMT]    =   {ATT_DESC_CHAR_PRES_FORMAT, PERM(RD, ENABLE), sizeof(struct prf_char_pres_fmt),
                                        0, NULL},
};

由上述定义我们来一个个分析bas_att_db的五个成员变量。

[BAS_IDX_SVC]

首先是[BAS_IDX_SVC]成员变量。
BAS_IDX_SVC的value是bas_svc 变量，具体如下：

const att_svc_desc_t bas_svc = ATT_SVC_BATTERY_SERVICE;

我们可以看到bas_svc 被赋值为一个枚举类型变量，具体值为0x180F。
类似的还有ATT_SVC_GENERIC_ACCESS、ATT_SVC_GENERIC_ATTRIBUTE、ATT_SVC_DEVICE_INFO、ATT_SVC_HID等。
具体定义如下：

/// Common 16-bit Universal Unique Identifier
enum {
    ATT_INVALID_UUID = 0,
    /*----------------- SERVICES ---------------------*/
    /// Generic Access Profile
    ATT_SVC_GENERIC_ACCESS                      = 0x1800,
    /// Attribute Profile
    ATT_SVC_GENERIC_ATTRIBUTE,
    ...
    /// Device Information Service
    ATT_SVC_DEVICE_INFO                         = 0x180A,
    ...
    /// Battery Service
    ATT_SVC_BATTERY_SERVICE,
    /// Blood Pressure Service
    ATT_SVC_BLOOD_PRESSURE                      = 0x1810,
    /// Alert Notification Service
    ATT_SVC_ALERT_NTF                           = 0x1811,
    /// HID Service
    ATT_SVC_HID                                 = 0x1812,
    ...
}

example

[BAS_IDX_BATT_LVL_CHAR]

关于BAS_IDX_BATT_LVL_CHAR成员，它的value比较特殊，是att_char_desc结构体变量强转为（uint8_t *）。该变量定义如下：

/// Battery Level characteristic
const struct att_char_desc bas_batt_level_char = ATT_CHAR(ATT_CHAR_PROP_RD, 0, ATT_CHAR_BATTERY_LEVEL);

struct att_char_desc定义如下：

/// Characteristic Value Descriptor
struct att_char_desc
{
    /// properties
    uint8_t prop;//属性
    /// attribute handle
    uint8_t attr_hdl[ATT_HANDLE_LEN];//句柄索引
    /// attribute type
    uint8_t attr_type[ATT_UUID_16_LEN];//UUID值
};

定义bas_batt_level_char变量时，使用ATT_CHAR宏函数填充结构体，原型如下

/// macro to fill an attribute characteristic
#define ATT_CHAR(prop, handle, type) {(prop),                                           \
                                     {(uint8_t)((handle)), (uint8_t)((handle) >> 8)},  \
                                     {(uint8_t)((type)), (uint8_t)((type) >> 8)}       };

[BAS_IDX_BATT_LVL_VAL]、[BAS_IDX_BATT_LVL_NTF_CFG]、[BAS_IDX_BATT_LVL_PRES_FMT]

这个三个变量都没填充value值

小结

成员	定义	描述
[BAS_IDX_SVC]	{ATT_DECL_PRIMARY_SERVICE,PERM(RD, ENABLE),sizeof(bas_svc),sizeof(bas_svc),(uint8_t *)&bas_svc}	Battery Service Declaration
[BAS_IDX_BATT_LVL_CHAR]	{ATT_DECL_CHARACTERISTIC, PERM(RD, ENABLE), sizeof(bas_batt_level_char),sizeof(bas_batt_level_char), (uint8_t *)&bas_batt_level_char}	Battery Level Characteristic Declaration
[BAS_IDX_BATT_LVL_VAL]	{ATT_CHAR_BATTERY_LEVEL, PERM(RD, ENABLE), sizeof(uint8_t),0, NULL}	Battery Level Characteristic Value
[BAS_IDX_BATT_LVL_NTF_CFG]	{ATT_DESC_CLIENT_CHAR_CFG,PERM(RD, ENABLE)\|PERM(WR, ENABLE),sizeof(uint16_t),0, NULL}	Battery Level Characteristic - Client Characteristic Configuration Descriptor
[BAS_IDX_BATT_LVL_PRES_FMT]	{ATT_DESC_CHAR_PRES_FORMAT, PERM(RD, ENABLE), sizeof(struct prf_char_pres_fmt),0, NULL}	Battery Level Characteristic - Characteristic Presentation Format Descriptor

Database类型总结

UUID	类型	值
ATT_DECL_PRIMARY_SERVICE	DECLARATIONS	0x2800
ATT_DECL_CHARACTERISTIC	DECLARATIONS	0x2803
ATT_CHAR_BATTERY_LEVEL	CHARACTERISTICS	0x2A19
ATT_DESC_CLIENT_CHAR_CFG	DESCRIPTORS	0x2902
ATT_DESC_CHAR_PRES_FORMAT	DESCRIPTORS	0x2904