Question

VB编写串口收发数据时出现8020错误

用串口助手时正常收发，提示是inbuf = MSComm1.Input有问题。
Private Sub Command1_Click()
Dim sj(4) As Byte
sj(0) = &HAA
sj(1) = &H55
sj(2) = &H5
sj(3) = &H5
sj(4) = &H9
MSComm1.Output = sj
End Sub

Private Sub Command2_Click()
Dim sj(4) As Byte
sj(0) = &HAA
sj(1) = &H55
sj(2) = &H5
sj(3) = &H7
sj(4) = &HB
MSComm1.Output = sj
End Sub

Private Sub Command3_Click()
Text1.Text = ""
End Sub

Private Sub Command4_Click()
MSComm1.PortOpen = False
Unload Me
End Sub

Private Sub Form_Load()
MSComm1.CommPort = 3
MSComm1.Settings = "9600,n,8,1"
MSComm1.InputMode = 1
MSComm1.RThreshold = 1 '设置并返回要接收的字符数
MSComm1.SThreshold = 1 '设置并返回发送缓冲区中允许的最小字符数
MSComm1.PortOpen = True
End Sub

Private Sub MSComm1_OnComm()
Select Case MSComm1.CommEvent
Case comEvCD
Case comEvCTS
Case comEvDSR
Case comEvRing
Case comEvReceive
Dim inbuf() As Byte, i%, buf$
buf = ""
inbuf = MSComm1.Input
Rev_num = UBound(inbuf)
ReDim lnum(0 To Rev_num) As Integer
For i = 0 To Rev_num
lnum(i) = inbuf(i)
buf = buf + Str(inbuf(i)) + " "
Next i
Text1.Text = Text1 + buf
Case comEvSend
End Select
End Sub
新人不知是啥问题，大神帮帮忙啊。

Answer 1

Private Sub MSComm1_OnComm()
    Select Case MSComm1.CommEvent
'    Case comEvCD
'    Case comEvCTS
'    Case comEvDSR
'    Case comEvRing
    Case comEvReceive
        Dim inbuf() As Byte, i%, buf$
        buf = ""
        inbuf = MSComm1.Input
        Rev_num = UBound(inbuf)
        ReDim lnum(0 To Rev_num) As Integer
        For i = 0 To Rev_num
            lnum(i) = inbuf(i)
            buf = buf + Str(inbuf(i)) + " "
        Next i
        Text1.Text = Text1 + buf
'    Case comEvSend
    End Select
End Sub

经测试，代码未发现问题。

追问

我同学可以运行这串代码，但是我一运行就出错。。。

追答

查看下你的COM口所用的硬件（估计是USB转的串口），不要收发同时进行。

Answer 2

彻底重装PL2303驱动. 因为PL2303 有好几个版本!!!!