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分享vb mscomm 接收不到数据
Private Sub Form_Load()
Dim i As Integer
If MSComm1.PortOpen = True Then
MSComm1.PortOpen = False
End If '先判断串口是否关闭，如果打开则关闭
MSComm1.CommPort = 5 'COM端口
MSComm1.Settings = "115200,n,8,1"
MSComm1.InputLen = 0 '读取接收缓冲区的所有字符
MSComm1.InputMode = comInputModeBinary '采用二进制传输
MSComm1.InBufferSize = 1024 '接受缓冲区为1024字节
MSComm1.OutBufferSize = 2048 '发送缓冲区位2048字节
MSComm1.InBufferCount = 0 '清空接受缓冲区
MSComm1.OutBufferCount = 0 '清空传输缓冲区
MSComm1.SThreshold = 0 '禁止发送事件
MSComm1.RThreshold = 1 '产生MSComm事件
Command2.Enabled = False '初始化时设置“关闭”按钮不可用
End Sub
Private Sub MSComm1_OnComm()
Dim inbyte() As Byte '存储接收串口数据
Dim buffer As String '存储处理后的串口数据
Dim lenbuffer As Integer '存储处理后的串口数据长度
Dim i As Integer '设置循环变量
Select Case MSComm1.CommEvent
Case comEvReceive
inbyte = MSComm1.Input
For i = LBound(inbyte) To UBound(inbyte)
If Len(Hex(inbyte(i))) = 1 Then
buffer = buffer + "0" + Hex(inbyte(i)) + Chr(32)
Else
buffer = buffer + Hex(inbyte(i)) + Chr(32)
End If
lenbuffer = Len(Replace(Trim(buffer), " ", ""))
Select Case lenbuffer
Case Is = 14
If CByte("&H" & (Mid(Replace(buffer, " ", ""), 1, 2))) = &HAA _
And "&H" & (Mid(Replace(buffer, " ", ""), 14 - 4 + 1, 2)) = &H42 _
And "&H" & (Mid(Replace(buffer, " ", ""), 14 - 2 + 1, 2)) = &H42 Then
If "&H" & (Mid(Replace(buffer, " ", ""), 14 - 12 + 1, 2)) = &H55 Then
If "&H" & (Mid(Replace(buffer, " ", ""), 14 - 10 + 1, 2)) = &H43 _
And "&H" & (Mid(Replace(buffer, " ", ""), 14 - 8 + 1, 2)) = &H47 _
And "&H" & (Mid(Replace(buffer, " ", ""), 14 - 6 + 1, 2)) = &H8A Then
Text2.Text = "测试通过"
End If
End If
End If
case is = 18
....... 省略
End Select
Next i
End Sub
想问下，为什么上位机接收不到数据？？？
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tornado_dai 2013-08-06
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不错，好用
赵4老师 2013-08-02
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推荐使用portmon软件辅助串口通讯调试。
tornado_dai 2013-08-01
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多谢分享
嗷嗷叫的老马 2013-07-31
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我一般的做法是,收到数据先检查长度,再与已存储的长度相加,看看是不是已经达到我要求的长度.
如果达到或超过,就进入处理流程.
处理流程里会找到有效数据的头与尾,并清空尾部数据以前的数据,保证未处理的数据是在缓冲区开头.
如此周而复始.
zdingyun 2013-07-30
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大于8字节以上是我这儿COM口硬件测试结果，LZ接收”aa 55 43 47 8a 42 42“7字节有丢字节现象，我这儿没遇见过。或许LZ的环境电磁干扰或上下位机波特率差异等因素导致。
zdingyun 2013-07-30
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接收数据是固定字节长度的话，由于可以设置MSComm1.RThreshold为固定字节长度，buffer定义于为过程变量，接收代码照你原先的是没问题的。
而接收不定长的字节，只能设置MSComm1.RThreshold = 1，而COM口硬件原因，大于8字节以上的数据到达COM口会多次触发OnComm事件，buffer定义于为过程变量会导致接收字节不完整有丢数据现象，所以buffer定义于为全局变量。
tornado_dai 2013-07-30
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多谢zdingyun ,
将buffer定于为全局变量的方法可以接收到完整数据，接收到下一组数据时，之前的数据还在，需做一下清空处理；
可不可以讲解一下我之前接收数据丢失以及用这钟方法的缘由？
tornado_dai 2013-07-29
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Private Sub Command1_Click() '打开串口
On Error GoTo Err
MSComm1.CommPort = CInt(Mid(C1.Text, 4, 1)) '选择端口号
If MSComm1.PortOpen = False Then
MSComm1.PortOpen = True
Text1.Text = "串口打开"
Command1.Enabled = False '设置“打开”按钮变灰
Command2.Enabled = True
Exit Sub
End If
Err:
MsgBox "端口被占用或无", vbCritical, "错误警告"
End Sub
串口打开代码如上，上面的按你说的改过试了，还是不能接收到数据。。。
zdingyun 2013-07-29
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从代码看COM口没打开。
OnComm事件代码缺
End Select
Next i位置错误
Private Sub Form_Load()
Dim i As Integer
If MSComm1.PortOpen = True Then
MSComm1.PortOpen = False
End If
MSComm1.CommPort = 1
MSComm1.Settings = "115200,n,8,1"
MSComm1.InputLen = 0
MSComm1.InputMode = comInputModeBinary
MSComm1.InBufferSize = 1024
MSComm1.OutBufferSize = 2048
MSComm1.InBufferCount = 0
MSComm1.OutBufferCount = 0
MSComm1.SThreshold = 0
MSComm1.RThreshold = 1
MSComm1.PortOpen = True '打开COM口
Command2.Enabled = False
End Sub
Private Sub MSComm1_OnComm()
Dim inbyte() As Byte
Dim buffer As String
Dim lenbuffer As Integer
Dim i As Integer
Select Case MSComm1.CommEvent
Case comEvReceive
inbyte = MSComm1.Input
For i = LBound(inbyte) To UBound(inbyte)
If Len(Hex(inbyte(i))) = 1 Then
buffer = buffer + "0" + Hex(inbyte(i)) + Chr(32)
Else
buffer = buffer + Hex(inbyte(i)) + Chr(32)
End If
Next i
lenbuffer = Len(Replace(Trim(buffer), " ", ""))
Select Case lenbuffer
Case Is = 14
If CByte("&H" & (Mid(Replace(buffer, " ", ""), 1, 2))) = &HAA _
And "&H" & (Mid(Replace(buffer, " ", ""), 14 - 4 + 1, 2)) = &H42 _
And "&H" & (Mid(Replace(buffer, " ", ""), 14 - 2 + 1, 2)) = &H42 Then
If "&H" & (Mid(Replace(buffer, " ", ""), 14 - 12 + 1, 2)) = &H55 Then
If "&H" & (Mid(Replace(buffer, " ", ""), 14 - 10 + 1, 2)) = &H43 _
And "&H" & (Mid(Replace(buffer, " ", ""), 14 - 8 + 1, 2)) = &H47 _
And "&H" & (Mid(Replace(buffer, " ", ""), 14 - 6 + 1, 2)) = &H8A Then
Text2.Text = "????"
End If
End If
End If
End Select
End Select
End Sub
zdingyun 2013-07-29
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将buffer定义为窗体变量
Option Explicit
Dim buffer As String
Private Sub Form_Load()
Dim i As Integer
If MSComm1.PortOpen = True Then
MSComm1.PortOpen = False
End If
MSComm1.CommPort = 1
MSComm1.Settings = "115200,n,8,1"
MSComm1.InputLen = 0
MSComm1.InputMode = comInputModeBinary
MSComm1.InBufferSize = 1024
MSComm1.OutBufferSize = 2048
MSComm1.InBufferCount = 0
MSComm1.OutBufferCount = 0
MSComm1.SThreshold = 0
MSComm1.RThreshold = 1
MSComm1.PortOpen = True '打开COM口
Command2.Enabled = False
End Sub
Private Sub MSComm1_OnComm()
Dim inbyte() As Byte
Dim lenbuffer As Integer
Dim i As Integer
Select Case MSComm1.CommEvent
Case comEvReceive
inbyte = MSComm1.Input
For i = LBound(inbyte) To UBound(inbyte)
If Len(Hex(inbyte(i))) = 1 Then
buffer = buffer + "0" + Hex(inbyte(i)) + Chr(32)
Else
buffer = buffer + Hex(inbyte(i)) + Chr(32)
End If
Next i
Text1 = buffer
lenbuffer = Len(Replace(Trim(buffer), " ", ""))
Select Case lenbuffer
Case Is = 14
If CByte("&H" & (Mid(Replace(buffer, " ", ""), 1, 2))) = &HAA _
And "&H" & (Mid(Replace(buffer, " ", ""), 14 - 4 + 1, 2)) = &H42 _
And "&H" & (Mid(Replace(buffer, " ", ""), 14 - 2 + 1, 2)) = &H42 Then
If "&H" & (Mid(Replace(buffer, " ", ""), 14 - 12 + 1, 2)) = &H55 Then
If "&H" & (Mid(Replace(buffer, " ", ""), 14 - 10 + 1, 2)) = &H43 _
And "&H" & (Mid(Replace(buffer, " ", ""), 14 - 8 + 1, 2)) = &H47 _
And "&H" & (Mid(Replace(buffer, " ", ""), 14 - 6 + 1, 2)) = &H8A Then
Text2.Text = "????"
End If
End If
End If
End Select
End Select
End Sub
tornado_dai 2013-07-29
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因为上位机需要处理的数据只有7字节和20字节两种情况，我修改成
Select Case MSComm1.CommEvent
Case comEvReceive
'***********************************
Do While MSComm1.InBufferCount <> 7 And MSComm1.InBufferCount <> 20
DoEvents
Loop
inbyte = MSComm1.Input
'***********************************
tornado_dai 2013-07-29
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因为上位机需要处理的数据只有7字节和20字节两种情况，我修改成[code=vb][/ Select Case MSComm1.CommEvent
Case comEvReceive
'***********************************
Do While MSComm1.InBufferCount <> 7 And MSComm1.InBufferCount <> 20
DoEvents
Loop
inbyte = MSComm1.Input
'***********************************]接收的数据就是完整的了，还是不解原来的为何数据丢失。。。如上修改后如果期间发送了不是7字节和20字节的数据，发送字节小于7，则是缓存数据到了7字节或20字节，才能收到数据，若是发送了一个2字节内容，再发送那个20字节的回复数据，就不能正确响应case事件了，显示收不到数据，因为加上缓存数据的2字节，此时为22字节，就直接不能处理了
tornado_dai 2013-07-29
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把[code=vb][/ For i = LBound(inbyte) To UBound(inbyte)
If Len(Hex(inbyte(i))) = 1 Then
buffer = buffer + "0" + Hex(inbyte(i)) + Chr(32)
Else
buffer = buffer + Hex(inbyte(i)) + Chr(32)
End If
Next i]
改为[code=vb][/buffer = buffer + Hex(inbyte(i)) + Chr(32)]
还是丢失数据，发送aa 55 43 47 8a 42 42 只收到55 43 47 8a 42 42
yachong 2013-07-29
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前几年有一次写一个小串口程序放到客户某机器上面接收一小段数据，也是楼主这个现象
后来丢掉MSCOMM，网上找了一段api读写串口的代码就没问题了。再后来也没再研究这个事。
of123 2013-07-29
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应该是上位机代码屏蔽掉了一些数据。
如果你要调试接收是否正常，把你那些判断条件什么的都注释掉，把接收到的所有数据都显示出来。
tornado_dai 2013-07-29
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显示出来看了，数据有缺失，
发送aa 43 47 8A 42 42的时候，只显示43 47 8A 42 42；发送aa 55 89 00 31 32 30 35 33 36 32 31 33 36 37 39 0f 05 42 42的时候，只显示89 00 31 32 30 35 33 36 32 31 33 36 37 39 0f 05 42 42，是哪里出问题了？
嗷嗷叫的老马 2013-07-29
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另外,代码写在[code=vb]这里[/code <---此处还有一个]
嗷嗷叫的老马 2013-07-29
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把收到的数据全部输出来显示,再与发送的数据相比较,看看到底是完全不对,还是顺序不对,还是有缺失,再进行下一步排查.
tornado_dai 2013-07-29
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请降低波特率调试代码，或许USB转RS232线质量有问题导致。[/quote]
确定USB转串口线没有问题，波特率调低试过，也是收到的数据不对，还有其他原因吗？是不是要判断一下数据有没有接收完成还是怎样的
zdingyun 2013-07-29
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请降低波特率调试代码，或许USB转RS232线质量有问题导致。
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