這壹句代表當串口接收到10個數據後產生中斷。
建議設為1試試。
Attend.MSComm2.InBufferSize = 40
這壹句建議設為4096
我只能說，很多USB接口轉串口的轉換器都是虛擬串口的軟中斷，在連續通訊時，幾乎是不能正常工作的。
以前買過的USB轉串口都是不能用，後來買PCI轉串口的立刻正常了。
剛剛測試完畢的串口接收測試，低速測試通過。
拷貝下列代碼保存為.frm即可。
用這個編譯測試看看是不是會收到多次數據。
VERSION 5.00
Object = "{648A5603-2C6E-101B-82B6-000000000014}#1.1#0"; "mscomm32.ocx"
Begin VB.Form Form1
BorderStyle = 3 'Fixed Dialog
Caption = "Form1"
ClientHeight = 6090
ClientLeft = 45
ClientTop = 330
ClientWidth = 5580
LinkTopic = "Form1"
MaxButton = 0 'False
MinButton = 0 'False
ScaleHeight = 6090
ScaleWidth = 5580
ShowInTaskbar = 0 'False
StartUpPosition = 3 '窗口缺省
Begin VB.ComboBox Combo1
Height = 300
Left = 2640
Style = 2 'Dropdown List
TabIndex = 4
Top = 5640
Width = 855
End
Begin VB.Timer Timer1
Enabled = 0 'False
Interval = 40
Left = 240
Top = 4560
End
Begin VB.CommandButton Command2
Caption = "清 除"
Height = 495
Left = 1440
TabIndex = 2
Top = 5400
Width = 975
End
Begin MSCommLib.MSComm MSComm1
Left = 840
Top = 4440
_ExtentX = 1005
_ExtentY = 1005
_Version = 393216
CommPort = 3
DTREnable = -1 'True
StopBits = 2
End
Begin VB.CommandButton Command1
Caption = "開 始"
Height = 495
Left = 120
TabIndex = 1
Top = 5400
Width = 1095
End
Begin VB.TextBox Text1
Height = 5055
Left = 120
MultiLine = -1 'True
ScrollBars = 2 'Vertical
TabIndex = 0
Top = 120
Width = 5295
End
Begin VB.Shape Shape1
BackColor = &H80000004&
BackStyle = 1 'Opaque
Height = 255
Left = 4920
Shape = 3 'Circle
Top = 5640
Width = 375
End
Begin VB.Label Label3
Caption = "Byte"
Height = 255
Left = 3600
TabIndex = 6
Top = 5640
Width = 495
End
Begin VB.Label Label2
Caption = "接收數據長度"
Height = 255
Left = 2640
TabIndex = 5
Top = 5280
Width = 1215
End
Begin VB.Label Label1
Alignment = 1 'Right Justify
AutoSize = -1 'True
Caption = "0 Byte"
Height = 180
Left = 3960
TabIndex = 3
Top = 5280
Width = 1380
End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Private Sub Combo1_Click()
MSComm1.InputLen = Combo1.ListIndex + 1
End Sub
Private Sub Command1_Click()
MSComm1.PortOpen = Not MSComm1.PortOpen
If MSComm1.PortOpen Then
Command1.Caption = "停 止"
Else
Command1.Caption = "開 始"
End If
End Sub
Private Sub Command2_Click()
Text1.Text = ""
Label1.Caption = "0 Byte"
End Sub
Private Sub Form_Load()
'通訊口初始化：
For i = 1 To 99
Combo1.AddItem i
Next
Combo1.ListIndex = 8
MSComm1.Settings = "9600,n,8,2"
MSComm1.CommPort = 3
MSComm1.InputMode = comInputModeBinary
MSComm1.InputLen = Combo1.ListIndex + 1
MSComm1.InBufferCount = 0
MSComm1.OutBufferCount = 0
MSComm1.RThreshold = Combo1.ListIndex + 1
MSComm1.InBufferSize = 4096
End Sub
Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
If MSComm1.PortOpen Then MSComm1.PortOpen = False
End Sub
'串口接收事件
Private Sub MSComm1_OnComm()
Dim inx() As Byte
Dim strTemp As String
Dim strTemp1 As String
Dim strLen As Byte
Select Case MSComm1.CommEvent
Case comEvReceive '判斷為接收事件
inx = MSComm1.Input '接收數據
MSComm1.InBufferCount = 0
MSComm1.RThreshold = Combo1.ListIndex + 1
For i = 0 To UBound(inx)
strTemp1 = Hex(inx(i))
If Len(strTemp1) > 1 Then
strTemp = strTemp & strTemp1 & " "
Else
strTemp = strTemp & "0" & strTemp1 & " "
End If
Next i
Text1.Text = Text1.Text & strTemp & vbCrLf
Text1.SelStart = Len(Text1.Text)
Label1.Caption = Str(Val(Label1.Caption) + i) & " Byte"
Erase inx
Shape1.BackColor = vbRed
Timer1.Enabled = True
End Select
End Sub
Private Sub Text1_Change()
If Len(Text1.Text) > 9999 Then Text1.Text = ""
End Sub
Private Sub Timer1_Timer()
Shape1.BackColor = &H80000004
Timer1.Enabled = False
End Sub