基于串口通信的PC机与GSM短信模块数据交互

Option Explicit 

' 全局变量声明
Public g_blIsListSMS As Boolean       ' 是否正在列出短信
Public g_blIsSysBusy As Boolean        ' 系统是否繁忙
Public g_blIsWaiting As Boolean        ' 是否处于等待状态
Public g_blIsNewSMSIn As Boolean      ' 是否有新短信
Public g_blIsSendingSMS As Boolean     ' 是否正在发送短信
Public g_blIsHexCommData As Boolean    ' 通信数据是否为十六进制格式
Public g_blMaySaveAllSMS As Boolean    ' 是否允许保存所有短信
Public g_blwav As Boolean            ' 是否启用声音提示
Public g_strSave As String             ' 保存路径
Public g_strThisAT As String          ' 当前 AT 命令
Public g_strLastAT As String          ' 上一条 AT 命令
Public g_strLatestAT As String         ' 最新 AT 命令
Public n_CountListSMS As Long         ' 短信列表计数器
Public g_SysInfo As SysStruct          ' 系统信息结构体
Public TheForm As Form                  ' 窗体对象
Public TheMenu As Menu                  ' 菜单对象

' 声明外部函数
Public Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long) ' VB延时API函数
Public Declare Sub winhelp Lib "user32" (ByVal hWnd As Long, ByVal lphelpfile As String, ByVal wcommand As Long, ByVal dwData As Long) ' 调用帮助API函数
Public Declare Function htmlHelp Lib "hhctrl.ocx" Alias "HtmlHelpA" (ByVal hwndCaller As Long, ByVal pszFile As String, ByVal uCommand As Long, ByVal dwData As Long) As Long 

' 常量定义
Public Const HH_DISPLAY_INDEX = 2 
Public Const HH_DISPLAY_TO 

' ... 其他代码 ... 

这段代码展示了PC机与GSM短信模块进行串口通信的部分关键变量和函数声明。通过这些声明，程序可以实现发送和接收短信、查询短信列表、设置模块参数等功能。代码中使用 Declare 语句声明了调用 Windows API 函数和外部库函数，例如 Sleep 用于延时，winhelp 用于调用帮助文档，htmlHelp 用于调用 HTML 帮助系统。代码还定义了一些常量，用于控制程序行为。