COM接收问题还没解决，请高手帮忙看看我的代码，万分感谢。
－－目的－－：
通过单击命令1，得到设备当前频率，并显示在Frequency.txt 文本框；
通过单击命令2，得到设备当前温度，并显示在Temp.txt 文本框；
－－－－问题如下－－－－：
（1）点击命令1的话，Frequency.txt 为空白；再按一次，正常了；
（2）点击命令2的话，Temp.txt 显示的是命令1的频率信息；然后再点击一下命令2，这时Temp.txt 显示正常；
－－－代码－－－－：
Private Sub Command1_Click() ' 初始化
MSComm1.CommPort = PortNo
MSComm1.Settings = "115200,n,8,1"
MSComm1.InputMode = comInputModeText ‘文本方式传输
MSComm1.InBufferCount = 0
MSComm1.OutBufferCount = 0
MSComm1.RThreshold = 1 '通过oncomm事件读取COM的返回值
MSComm1.PortOpen = True
MSComm1.InputLen = 0
End Sub
Private Sub Command1_Click() ’1命令－得到设备当前频率
If MSComm1.PortOpen = True Then
MSComm1.Output = vbLf & "r?"
Frequency.Text = result
result = ""
End If
End Sub
Private Sub Command2_Click() ‘2命令－得到设备当前温度
If MSComm1.PortOpen = True Then
MSComm1.Output = vbLf & "t?"
Temp.Text = result
result = ""
End If
End Sub
Private Sub MSComm1_OnComm()
If (MSComm1.CommEvent = comEvReceive) Then
result = result & Trim(MSComm1.Input)
End If
MSComm1.InBufferCount = 0
MSComm1.OutBufferCount = 0
End Sub
应该按一次命令按钮就能得到正确的信息才行啊，
请问这是怎么回事？怎么解决啊？
[解决办法]
Dim blnIsFreq As Boolean
Private Sub Form_Load() ' 初始化
MSComm1.CommPort = PortNo
MSComm1.Settings = "115200,n,8,1"
MSComm1.InputMode = comInputModeText ‘文本方式传输
MSComm1.InBufferCount = 0
MSComm1.OutBufferCount = 0
MSComm1.RThreshold = 1 '通过oncomm事件读取COM的返回值
MSComm1.PortOpen = True
MSComm1.InputLen = 0
End Sub
Private Sub Command1_Click() ’1命令－得到设备当前频率
If MSComm1.PortOpen = True Then
MSComm1.Output = vbLf & "r?"
End If
End Sub
Private Sub Command2_Click() ‘2命令－得到设备当前温度
If MSComm1.PortOpen = True Then
MSComm1.Output = vbLf & "t?"
End If
End Sub
Private Sub MSComm1_OnComm()
If (MSComm1.CommEvent = comEvReceive) Then
result = Trim(MSComm1.Input)
If blnIsFreq Then
Frequency.Text = Frequency.Text & result
Else
Temp.Text = Temp.Text & result
End If
End If
End Sub
结构还是不太好。最好能够判断已经接收到完整的信息，一次提取。
[解决办法]
- VB code
Option Explicit Dim result As String Dim strSend As StringPrivate Sub Command1_Click() '1命令－得到设备当前频率 If MSComm1.PortOpen = True Then strSend = vbLf & "r?" MSComm1.Output = strSend End IfEnd SubPrivate Sub Command2_Click() '2命令－得到设备当前温度 If MSComm1.PortOpen = True Then strSend = vbLf & "t?" MSComm1.Output = strSend End IfEnd SubPrivate Sub Form_Load() MSComm1.CommPort = 1 'PortNo MSComm1.Settings = "9600,n,8,1" MSComm1.InputMode = comInputModeText '文本方式传输 MSComm1.InBufferCount = 0 MSComm1.OutBufferCount = 0 MSComm1.RThreshold = 1 '通过oncomm事件读取COM的返回值 MSComm1.PortOpen = True MSComm1.InputLen = 0End SubPrivate Sub MSComm1_OnComm() Select Case MSComm1.CommEvent Case comEvReceive result = result & Trim(MSComm1.Input) If strSend = vbLf & "r?" Then Frequency.Text = result result = "" ElseIf strSend = vbLf & "t?" Then Temp.Text = result result = "" End If MSComm1.InBufferCount = 0 MSComm1.OutBufferCount = 0 End SelectEnd Sub
[解决办法]
存在两个问题
1)在 Command1_Click() 中发出命令后不能期望马上得到回复
2)每收到一个字符就会触发 MSComm1_OnComm() 事件
- VB code
Option ExplicitPrivate m_Mode As LongPrivate result As StringPrivate Sub Form_Load() MSComm1.CommPort = PortNo MSComm1.Settings = "115200,n,8,1" MSComm1.InputMode = comInputModeText MSComm1.InBufferCount = 0 MSComm1.OutBufferCount = 0 MSComm1.RThreshold = 1 MSComm1.PortOpen = True MSComm1.InputLen = 0End SubPrivate Sub Command1_Click() If MSComm1.PortOpen = True Then m_Mode = 1 result = vbNullString MSComm1.InBufferCount = 0 MSComm1.Output = vbLf & "r?" End IfEnd SubPrivate Sub Command2_Click() If MSComm1.PortOpen = True Then m_Mode = 2 result = vbNullString MSComm1.InBufferCount = 0 MSComm1.Output = vbLf & "t?" End IfEnd SubPrivate Sub MSComm1_OnComm() If (MSComm1.CommEvent = comEvReceive) Then result = result & MSComm1.Input Select Case m_Mode Case 1: Frequency.Text = result Case 2: Temp.Text = result End Select End IfEnd Sub
[解决办法]