LRC Computation Help
Good day.
I am searching for a function in VB.NET to get the LRC for a HEX result.
For instance, I have the following HEX values (I included spaces for reability only):
01 30 02 42 20 21 20 03 The LRC result is 53
what kind of VB.NET function can be written to computer this LRC?
Thank you for your help.
I am searching for a function in VB.NET to get the LRC for a HEX result.
For instance, I have the following HEX values (I included spaces for reability only):
01 30 02 42 20 21 20 03 The LRC result is 53
what kind of VB.NET function can be written to computer this LRC?
Thank you for your help.
Jeff Certain
If you explain LRC, we'll find something :)
Are your hex values in a string? An array? A file?
ASKER
LRC = Longitudinal Redundancy Check
The hex values are in a string which are received from a COM port.
The hex values are in a string which are received from a COM port.
Something like the following (but I get 33 as a result):
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
' 01 30 02 42 20 21 20 03 The LRC result is 53
Dim MyString As String
MyString = Chr(1)
MyString &= Chr(30)
MyString &= Chr(2)
MyString &= Chr(42)
MyString &= Chr(20)
MyString &= Chr(21)
MyString &= Chr(20)
MyString &= Chr(3)
MessageBox.Show("Result is: " & CalculateLRC(MyString))
End Sub
Public Function CalculateLRC(ByVal S As String) As Byte
CalculateLRC = 0
For Index As Integer = 1 To Len(S)
CalculateLRC = CByte(CalculateLRC Xor Asc(Mid(S, Index, 1)))
Next
End Function
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
' 01 30 02 42 20 21 20 03 The LRC result is 53
Dim MyString As String
MyString = Chr(1)
MyString &= Chr(30)
MyString &= Chr(2)
MyString &= Chr(42)
MyString &= Chr(20)
MyString &= Chr(21)
MyString &= Chr(20)
MyString &= Chr(3)
MessageBox.Show("Result is: " & CalculateLRC(MyString))
End Sub
Public Function CalculateLRC(ByVal S As String) As Byte
CalculateLRC = 0
For Index As Integer = 1 To Len(S)
CalculateLRC = CByte(CalculateLRC Xor Asc(Mid(S, Index, 1)))
Next
End Function
ASKER
hmmmm...
00000001 (01)
00110000 (30)
00000010 (02)
01000010 (42)
00100000 (20)
00100001 (21)
00100000 (20)
00000011 (03)
-----------
01010011 = 53
00000001 (01)
00110000 (30)
00000010 (02)
01000010 (42)
00100000 (20)
00100001 (21)
00100000 (20)
00000011 (03)
-----------
01010011 = 53
Try this...
Function getLRC(message As String) As String
Dim i As Integer
Dim mlength As Integer
Dim lrc As Integer
Dim cchar As String
lrc = 0
i = 1 'set start position
mlenght = Len(message)
Do While i <= mlenght
cchar = (Mid$(message, i, 1))
lrc = Asc(cchar) Xor lrc
i = i + 1
Loop
getLRC = Chr$(lrc)
End Function
Funny what Google turns up... https://www.experts-exchange.com/questions/20732543/MSComm-xor-LRC.html
Function getLRC(message As String) As String
Dim i As Integer
Dim mlength As Integer
Dim lrc As Integer
Dim cchar As String
lrc = 0
i = 1 'set start position
mlenght = Len(message)
Do While i <= mlenght
cchar = (Mid$(message, i, 1))
lrc = Asc(cchar) Xor lrc
i = i + 1
Loop
getLRC = Chr$(lrc)
End Function
Funny what Google turns up... https://www.experts-exchange.com/questions/20732543/MSComm-xor-LRC.html
I think you should be starting with 00000000 and THEN xor'ing 00000001, right?
Strike that, duh. Let me see why it's different.
ASKER
i tried the one you have, Chaosian, and it returns an exclamation mark. i tried it last night it couldn't get it to work.
GivenRandy: I tried your function against another string and it was off by 20 again.
GivenRandy: I tried your function against another string and it was off by 20 again.
Duh, because it's hex. More like this:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
' 01 30 02 42 20 21 20 03 The LRC result is 53
Dim MyString As String
MyString = Chr(&H1)
MyString &= Chr(&H30)
MyString &= Chr(&H2)
MyString &= Chr(&H42)
MyString &= Chr(&H20)
MyString &= Chr(&H21)
MyString &= Chr(&H20)
MyString &= Chr(&H3)
MessageBox.Show("Result is: " & CalculateLRC(MyString))
End Sub
Public Function CalculateLRC(ByVal S As String) As Byte
CalculateLRC = 0
For Index As Integer = 1 To Len(S)
CalculateLRC = CByte(CalculateLRC Xor Asc(Mid(S, Index, 1)))
Next
End Function
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
' 01 30 02 42 20 21 20 03 The LRC result is 53
Dim MyString As String
MyString = Chr(&H1)
MyString &= Chr(&H30)
MyString &= Chr(&H2)
MyString &= Chr(&H42)
MyString &= Chr(&H20)
MyString &= Chr(&H21)
MyString &= Chr(&H20)
MyString &= Chr(&H3)
MessageBox.Show("Result is: " & CalculateLRC(MyString))
End Sub
Public Function CalculateLRC(ByVal S As String) As Byte
CalculateLRC = 0
For Index As Integer = 1 To Len(S)
CalculateLRC = CByte(CalculateLRC Xor Asc(Mid(S, Index, 1)))
Next
End Function
It returns 83, which is 53H. The CalculateLRC() function is unchanged. I just had the wrong input values going into it.
If you wanted the hex conversion:
MessageBox.Show("Result is: " & Hex(CalculateLRC(MyString)
MessageBox.Show("Result is: " & Hex(CalculateLRC(MyString)
ASKER CERTIFIED SOLUTION
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ASKER
fantastic.
the one item i added was
Return Hex(CalculateLRC) at the end of the calculateLRC function as i need to include this in the string i send....
i appreciate the quick response and clean code.
have a good one.
the one item i added was
Return Hex(CalculateLRC) at the end of the calculateLRC function as i need to include this in the string i send....
i appreciate the quick response and clean code.
have a good one.
well, thgat one's returning a string. Wonder if ! is Chr(53)?
ASKER
sometimes when the answer is obvious, it's overlooked, Chaosian.