串口发信息和收信息比较特别的问题
我想的是：首先发Y，看是否读到P，若成功，则后面发P、U、F，分别将值读出。然后，再发Y，周而复始，
若中途或一开始发Y，读不到P，则连续发十次，再收不到则报警。
还请指点。
Dim binP As Boolean '电源通信是否握手成功，则接着发后面的..
Dim Varp2, Varp3 As String '判断串口能否收到S 电源是否在线
'我用了二个定时器，一个发“Y”，另一个，初始关闭，待确认电源在线后，再打开，发送后面的.
Private Sub Form_Load()
MyCom1 MSComm2 ‘调用串口
timer2.enabled=flase '2号定时器不能用
Varp2 = "S"
End Sub
'向电源发送握手信息
Private Sub Timer5_Timer()
MSComm2.Output = "Y"
End Sub
'串口事件
Private Sub MSComm2_OnComm()
Call Sleep(50) '延时
If MSComm2.CommEvent = 2 Then
MSComm2.RThreshold = 20
Dim i
For i = 1 To MSComm2.InBufferCount
SwichVar1 i ’将不定长的数据一个个接起来
buffer1 = buffer1 & Hex(InByte(i))
Next i
Varp3 = HexToStr(buffer1)'将收到的转成STR
Text1.Text = Varp3 '此处是监测点
End If
If StrComp(Varp2, Varp3, vbBinaryCompare) = 0 Then '若相同
POWER1Alarm.FillColor = QBColor(10) ‘灯变绿
binP = True '变量为真
Timer1.Enabled = False '关闭1号定时器
Timer6.Enabled = True '打开2号定时器
Else
UPS1Alarm.FillColor = QBColor(12)
binADDRS = False
Timer6.Enabled = False
End If
若不加这一段，则发送没有问题，若我后面发“P”，读出的值也就是“150”功率，此值也就不等于“S”。这时，程序就停了，好像这里有点乱。
（ If temp = 1 Then
Varp3 = HexToStr(buffer1)
Text2.Text = Varp3 '监测点二
End If ）
buffer1 = ""
MSComm2.RThreshold = 1
End Sub
'向电源发送读命令
Private Sub Timer6_Timer()
If binADDRS = True Then
temp = temp + 1
If temp = 1 Then
MSComm2.Output = "P" '读功率值
ElseIf temp = 2 Then
MSComm2.Output = "U" '读电压值
ElseIf temp = 3 Then
MSComm2.Output = "f" '读频率值
End If
If temp > 3 Then temp = 0
End If
End Sub
[解决办法]
Public Status As Boolean
Dim Smsg(2) As String
Dim msgNext As Byte
Private Sub Form_Load()
MSComm1.PortOpen = True
Status = False
Smsg(0) = "P"
Smsg(1) = "U"
Smsg(2) = "F"
'msgNext = 0
End Sub
Private Sub MSComm1_OnComm()
Dim tmp
Dim curr As Byte
tmp = MSComm1.Input
If tmp = "S" Then
Status = True
msgNext = 0
'Exit Sub
Else 'If Status Then
Select Case msgNext
Case 0
Text1.Text = Text1.Text & Smsg(msgNext) & " = " & (tmp)
Case 1
Text1.Text = Text1.Text & ", " & Smsg(msgNext) & " = " & (tmp)
Case 2
Text1.Text = Text1.Text & ", " & Smsg(msgNext) & " = " & (tmp) & vbCrLf
End Select
msgNext = msgNext + 1
If msgNext = 3 Then
msgNext = 0
Status = False
End If
End If
End Sub
Private Sub Timer1_Timer()
If Not Status Then
MSComm1.Output = "Y"
msgNext = 0
Else
Select Case msgNext
Case 0
MSComm1.Output = Smsg(msgNext)
Case 1
MSComm1.Output = Smsg(msgNext)
Case 2
MSComm1.Output = Smsg(msgNext)
'Status = False
End Select
End If
'Timer1.Enabled = False
End Sub