Change This Checksum Function To Accept An Integer Input Instead Of A String?
Dec 31, 2009
This function doesn't work if I change the input argument 'pdu' from a string to an int.Would someone please help me figure out what to do here so that the checksum does not add the ascii value of the int argument but rather the actual integer value?I took out a few lines of the actual function but it adds the input argument to a packet sent out via TCP protocol.This function shows the integer value just fine in the string that gets encoded as a byte array. the checksum is wrong.!
''Public Function buildpacket(pdu As Integer) is what I want.
Public Function buildpacket(pdu As String)
Dim packet As String
I have been trying to compute the checksum for a line of hex code. This is to create a hex file which will be loaded onto an embedded micro.Some of you guys may not know how this is done so very briefly:
The underlined bytes are taken and summed. (in this case the decimal 960). and the bold is the checksum Only the 8LSB (or single least significant byte) is needed to compute the checksum... which in this case, 960 = 03C0 in hex, so only C0 is needed.Two's complement is then taken:
step 1) logical not of C0 which is step 2) add one (integer) BIN...........DEC...HEX
[code]....
So here is the code I have been using: (quick mention that in the string passed, the hex bytes are all grouped together, there are no space characters)
Public Sub CreateLine(ByVal Data As String) 'Dim BDataArray(DataLength) As Byte Dim IDataArray(Data.Length) As Integer
[code]....
where i get into trouble is where i commented 'i get into trouble'. My code works, but it's rather crude Now, in that line i first convert the hex value (string) "SChecksum" into an integer. I want to NOT this, so I get my step 2 from my explanation. However, the results appears to be a signed logical NOT. which gives me the wrong answer. My hashed togther version simply subtracts 256 before the not, in order to give me the correct answer.
Basically, I would love for someone to chime in and point out the flaws in my function, and push me towards figuring out the 'proper' way of doing this. Also I can't quite wrap my head around what would happen in the case a string were passed to my function that is over 16 bits, but I imagine I would have to subtract a larger value than 256, before doing the NOT in this case?(whilst we're on the subject of functions, I've used a 'sub', in which case should I used a sub, and which case should I use a function?).
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Here's the block of code I have so far:
Private Sub TextBox1_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyDown If (e.KeyCode >= Keys.D0 OrElse e.KeyCode >= Keys.NumPad0) And (e.KeyCode <= Keys.D9 OrElse e.KeyCode <= Keys.NumPad9) Then Select Case e.KeyCode
[code]....
I can't get vb to recognize the above code it seems to skip right over it. BTW, is 'Keys.Crsel' the same as the caret '^' symbol?
I need to convert a string to get a checksum as follows;
Checksum
The checksum is the 8 LSB (least significant bits) of a simple addition of all octets (note that a message type '30' is two octets with the values 33 hex and 30 hex) following the STX character and until the checksum field. Note that all separators will be included in the checksum, but the STX, checksum and the ETX will not be included.
Dim str as string = "01/00064/O/30/12345678/87654321////////48656C6C6F20576F726C64/"
This should result in checksum = "C2" What type of checksum is this? what should I Google for? CRC, MD5, hash ?
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The code looks something like this If (object.one = ... ) ... End if If (object.two = ... ) ... End if If (object.three = ... ) ... End if
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Public Class frmHarrysGroceryCalculator Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click 'exit button ep
[code]....
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The following is a sample application's input section [code]...
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Public Class Form1 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
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[[code] 1) Is this violating the phrase static classes should not have state?
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EDIT:
Public Class Form1 ... Private Sub mysub(ByVal sender As Object, ByVal e As System.EventArgs, ByVal str As String)[code]......
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Sub GetStatistics(ByVal ProductNumbers As List(Of String), ByRef Passed As Integer, ByRef FailedProducts As List(Of String)) Passed = 0 FailedProducts = Nothing
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Public Function CatchString(ByVal stringValue As String) As String If stringValue = "" Or stringValue Is Nothing Or stringValue Is DBNull.Value Then Return "null"[code].....
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