真的用过serialport类的老大，请帮忙指点一下

[peipeter007]

我在使用serialport时出现些问题，请大家提供些帮助。
程序设计的思路是用串口连接一台单片机，上位机对单片机进行定时查询，单片机返回当前DI和其他端口的状态，如果检测到DI的某一位发生变化，在将对应的DO状态，发送到单片机。
如：Private Sub Timer1_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles Timer1.Tick
'Button1_Click(Nothing, Nothing)
Dim byteData As Byte() = New Byte(4) {}
byteData(0) = &H32
byteData(1) = &H1
byteData(2) = &H0
byteData(3) = &H0
byteData(4) = &H33


Try
If SerialPort1.IsOpen = False Then
SerialPort1.Open()
End If
SerialPort1.Write(byteData, 0, 5)
Catch ex As Exception
MsgBox("1 " & ex.Message)
End Try

End Sub

[peipeter007]

Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
Dim display As New Display(AddressOf DisplayResults)
'Dim s As String = String.Empty

Dim i As Integer

'''2222222222222222222222222222222
s = ""

databyte(num) = SerialPort1.ReadByte()
num += 1
If num = 8 Then
If databyte(7) = (CInt(databyte(0)) + CInt(databyte(1)) + CInt(databyte(2)) + CInt(databyte(3)) + CInt(databyte(4)) + CInt(databyte(5)) + CInt(databyte(6)) Mod 256) Then
s = Hex(databyte(0)) & " " & Hex(databyte(1)) & " " & Hex(databyte(2)) & " " & Hex(databyte(3)) _
& " " & Hex(databyte(4)) & " " & Hex(databyte(5)) & " " & Hex(databyte(6)) & " " & Hex(databyte(7))
count += 1


Me.Invoke(display, New Object() {s, CStr(count), databyte})

Else
's = "错误"
SerialPort1.DiscardInBuffer()

errorcount += 1
'Me.Invoke(display, New Object() {s, CStr("********"), False})

End If
num = 0

End If

[peipeter007]

Private Sub DisplayResults(ByVal s As String, ByVal strCount2 As String, ByVal databyte() As Byte)
Dim byteData As Byte() = New Byte(4) {}
If DITranslate(databyte(4)) And &H1 Then
bispaperbreak = True
If prepaperbreak = False Then
byteData(0) = &H31
byteData(1) = &H1
byteData(2) = &H1
byteData(3) = &H1B
byteData(4) = CInt(byteData(0)) + CInt(byteData(1)) + CInt(byteData(2)) + CInt(byteData(3)) Mod 256
prepaperbreak = True
'Timer1.Stop()
Timer1.Enabled = False
Try
If SerialPort1.IsOpen = False Then
SerialPort1.Open()
End If
'SerialPort1.DiscardInBuffer()
' SerialPort1.DiscardOutBuffer()

SerialPort1.Write(byteData, 0, 5)

Timer1.Enabled = True
Catch ex As Exception
MsgBox("3" & ex.Message)
End Try
End If

Else
bispaperbreak = False
If prepaperbreak = True Then
byteData(0) = &H31
byteData(1) = &H1
byteData(2) = &H1
byteData(3) = &H15
byteData(4) = CInt(byteData(0)) + CInt(byteData(1)) + CInt(byteData(2)) + CInt(byteData(3)) Mod 256
prepaperbreak = False

Timer1.Enabled = False
Try
If SerialPort1.IsOpen = False Then
SerialPort1.Open()
End If

SerialPort1.Write(byteData, 0, 5)


Timer1.Enabled = True

Catch ex As Exception
MsgBox("3" & ex.Message)
End Try
End If
End If

End Sub

[peipeter007]

问题就是，查询命令和控制命令可能相对同时发送，造成竞争，导致发送命令没有成功，串口也就收不到数据。我尝试在发送控制命令的时候，将定时器停止，待发送完成后在打开，实际有一定效果，但感觉不稳定，会出现查询命令不能定时发送。
哪位大侠做过这样的工作，可以和我分享一下吗，到底采用什么机制才可以准确稳定的运行。谢谢

[leitin]

存在invoke时，你要注意timer的操作顺序
dataarrive时,invoke未运行结束时，timer操作不能

[xuxiaopeng306]

这个问题我也想了很久．希望有高人提点一下．