'---------------------------------------------------------------------------------------
' Procedure : HexToInt
' DateTime : 07/11/2003 12:54
' Author : Matthew Knight
' Purpose : Rather Brute Hex to Int Conversion
' : Assumes that the string will be 2 valid hex char long
'---------------------------------------------------------------------------------------
'
Public Function HexToInt(strSub As String) As Integer
Dim intResult As Integer
intResult = (16 * HX(Left$(strSub, 1))) + HX(Right$(strSub, 1))
HexToInt = intResult
End Function
Public Function HX(strSub As String) As Integer
'---------------------------------------------------------------------------------------
' Procedure : HX
' DateTime : 07/11/2003 12:54
' Author : Matthew Knight
' Purpose : even more Brute Hex to Int Conversion
' : Assumes single valid hex char
'---------------------------------------------------------------------------------------
'
Dim intResult As Integer
Select Case strSub
Case "A"
intResult = 10
Case "B"
intResult = 11
Case "C"
intResult = 12
Case "D"
intResult = 13
Case "E"
intResult = 14
Case "F"
intResult = 15
Case Else
intResult = CInt(strSub)
End Select
HX = intResult
End Function
'---------------------------------------------------------------------------------------
' Procedure : CalculateBCC
' DateTime : 07/11/2003 12:56
' Author : Matthew Knight
' Purpose : Calculate BCC for stream of data
' : assumes STB has been removed
'---------------------------------------------------------------------------------------
'
Public Function CalculateBCC(strStream As String) As String
Dim intStringLen As Integer, intCount As Integer, intSub As Integer
Dim strSub As String
Dim intBCC As Integer, blnSkippedControl As Boolean
intStringLen = Len(strStream)
For intCount = 1 To intStringLen Step 2
'Get our byte value
strSub = UCase$(Mid$(strStream, intCount, 2))
'Convert to decimal integer
intSub = HexToInt(strSub)
If intSub = 16 And blnSkippedControl = False Then
'Set our flag to show we found a control code
'need to cope with situation where &H10 is valid data
'i.e. stream would look like ...1010...
blnSkippedControl = True
Else
' XOR this byte with result
intBCC = intBCC Xor intSub
blnSkippedControl = False
End If
Next intCount
'convert to hex and return
CalculateBCC = Hex$(intBCC)
End Function
is not equal to 0...![[soapbox]](/data/assets/smilies/soapbox.gif "[soapbox] [soapbox]")
is NOT 0. The problem is that characters actually don't arrive at the COM port as a string (and string being "readable data". But when reading it through the usual VB controls, you'll get a string, won't you? And this string, when printed contains the most serious rubbish you've ever seen, since it is not meant to be a readable string. So when anyone sending an actual 0 (ascii 0) into his/her COM port, the string returned from the receiving COM port will actually be this ascii 0 and not the ascii 48 (which would be a readable "0", if I'm not mistaking..).. People don't send over data this way. At least, I wouldn't (and I've also never seen data being send over that way). And EVEN if this would be the case, you'd still have to calculate the BCC like I did, since these are the acutal bytes that have been send / are to be send. After all; it's all about checking if the same data that has been send, also has arrived, isn't it?
