我的vb串口代码

'------------------COM ----------
Dim COM_NO As Byte
Dim DELAY As Long
Dim TXCNT As Long
Dim RXCNT As Long
Dim TOTALTX As Long
'-----------------------------
Private Sub Form_Load()
On Error GoTo err
'-------------CHECK THE COM-------------
Dim i As Integer
For i = 1 To 16
    MSComm1.CommPort = i
    On Error Resume Next
    MSComm1.PortOpen = True
    If err.Number = 0 Then
      COM_NO = i
    Else
     MSComm1.PortOpen = False
    End If
Next i
'-----------------------------------------
MSComm1.CommPort = COM_NO
If MSComm1.PortOpen = True Then MSComm1.PortOpen = False
If MSComm1.PortOpen = False Then
        MSComm1.Settings = "9600,n,8,1"
        MSComm1.RThreshold = 1      '******核心语句，去掉则无法触发
        'MSComm1.SThreshold = 1      '发送缓冲区中允许的最小字符数触发
        MSComm1.OutBufferSize = 10
        MSComm1.InputLen = 0    '***********CHANGEED
        MSComm1.InputMode = comInputModeBinary   '1--
        'MSComm1.InputMode = comInputModeText
        MSComm1.PortOpen = True     '---------------------------------
End If
If MSComm1.PortOpen = False Then MsgBox "串口打开失败，请检查": End
Exit Sub
err:
MsgBox "串口错误"
End Sub

Private Sub MSComm1_OnComm()
Dim Instring As Byte
Dim ins As String
Dim RE_BUF As Double
On Error GoTo err

Select Case MSComm1.CommEvent
    Case comEvReceive
    Dim InByte, i As Integer
    InByte = MSComm1.Input
    For i = 0 To UBound(InByte)
    Instring = (InByte(i))
    Next
    End Select
If Instring = 255 And FUNC = "CHOSE" Then MAIN_PWM = True: MsgBox "PWM设置成功": Exit Sub

If Instring < 5 And FUNC = "CHOSE" Then
If Instring = 1 Then CH1 = True: Form5.Text1.Text = Form5.Text1.Text + "通道1 OK"
If Instring = 2 Then CH2 = True: Form5.Text1.Text = Form5.Text1.Text + "通道2 OK"
If Instring = 3 Then CH3 = True: Form5.Text1.Text = Form5.Text1.Text + "通道3 OK"
If Instring = 4 Then CH4 = True: Form5.Text1.Text = Form5.Text1.Text + "通道4 OK"
Exit Sub
Else
End If

Instring = Hex(Instring)

If Instring > 10 And Instring < 18 Then
If Instring = 11 Then CH1_STEP = 1
 If Instring = 12 Then CH1_STEP = 3
  If Instring = 13 Then CH1_STEP = 2
   If Instring = 14 Then CH1_STEP = 4
    If Instring = 15 Then CH1_STEP = 6
     If Instring = 16 Then CH1_STEP = 5
          If Instring = 17 Then CH1_STEP = 7
If CH1_STEP > 0 Then Form8.Show
If CH1_STEP > 0 Then Form8.Command1.Value = True
Exit Sub
Else
End If

If Instring > 20 And Instring < 28 Then
If Instring = 21 Then CH3_STEP = 1
If Instring = 22 Then CH3_STEP = 3
If Instring = 23 Then CH3_STEP = 2
If Instring = 24 Then CH3_STEP = 4
If Instring = 25 Then CH3_STEP = 6
If Instring = 26 Then CH3_STEP = 5
If Instring = 27 Then CH3_STEP = 7
If CH3_STEP > 0 Then Form10.Show
If CH3_STEP > 0 Then Form10.Command1.Value = True
Exit Sub
Else
End If


If Instring > 30 And Instring < 38 Then
If Instring = 31 Then CH2_STEP = 1
 If Instring = 32 Then CH2_STEP = 3
  If Instring = 33 Then CH2_STEP = 2
   If Instring = 34 Then CH2_STEP = 4
    If Instring = 35 Then CH2_STEP = 6
     If Instring = 36 Then CH2_STEP = 5
          If Instring = 37 Then CH2_STEP = 7
If CH2_STEP > 0 Then Form9.Show
If CH2_STEP > 0 Then Form9.Command1.Value = True
Exit Sub
Else
End If


If Instring > 40 And Instring < 48 Then
If Instring = 41 Then CH4_STEP = 1
If Instring = 42 Then CH4_STEP = 3
If Instring = 43 Then CH4_STEP = 2
If Instring = 44 Then CH4_STEP = 4
If Instring = 45 Then CH4_STEP = 6
If Instring = 46 Then CH4_STEP = 5
If Instring = 47 Then CH4_STEP = 7
If CH4_STEP > 0 Then Form11.Show
If CH4_STEP > 0 Then Form11.Command1.Value = True
Else
End If
Exit Sub
err:
MSComm1.InBufferCount = 0
Call cominit
End Sub

'发送函数做的是全局函数，调用的form2的com控件
Public Function RS232_SEND(SEND_COUNT As Integer)
If Form2.MSComm1.PortOpen = False Then Form2.MSComm1.PortOpen = True
Form2.MSComm1.OutBufferCount = 0
'Debug.Print "start"
Dim i
For i = 1 To SEND_COUNT
Dim cc(0) As Byte
cc(0) = RS232_SEND_BUFFER(i - 1)
Form2.MSComm1.Output = cc
Debug.Print RS232_SEND_BUFFER(i - 1)
Next i
'Debug.Print "end"
End Function

串口会出现假死机的现象
初步怀疑是软体原因
我在接收程序中作了修改
一旦开始接收就把MSComm1.RThreshold = 0 暂时停止接收触发

如果接收出错则清空接受区，重新初始化串口

接收缓冲区设置为40，inputleng设置为1

看效果如何

如果还不行就考虑是下位机pic单片机的问题