Hex and Ascii issue converting back and forth from text and ascii

Cory Kimble

I need help converting between hex, ascii and back. I want to type in an alpha numeric like "ABC123" and save as a HEX formatted like this "## ## ## ## ## ## ## ## ## ## ## ##" Then later read that stored value and return to the text of "ABC123" I am having trouble reading it and returning to text. Here is what I try.

value = value.Replace(" ", "")

    While (zero)
        shorthex = value.Substring(0, 2)
        If shorthex = "00" Then
            value = value.Substring(2, value.Length - 2)


        Else
            zero = False
        End If
        i = i + 1
    End While
    Dim b((value.Length / 2) - 1) As Byte
    Dim x As Integer = b.Length - 1
    For i = value.Length - 2 To 0 Step -2
        b(x) = value.Substring(i, 2)
        x = x - 1
    Next

    value = Long.Parse(value, Globalization.NumberStyles.HexNumber)

    Dim test As String = System.Text.Encoding.ASCII.GetString(b)

When this is done test does not show the valid Text. Any suggestions?

I can't think of anything cool and nerdy to say.

Luc Pattyn

Hi Cory, your question is not really clear to me. How would you turn a six-char string ABC123 into a 24-char string (ignoring spaces)?? Please provide a full example, and/or provide the code that does the expansion. Anyway, here are some comments on the code shown: 1. the code is not safe, what if value starts of with all zeroes in it? 2. Long.Parse is returning a Long, you shouldn't assign the result to value since that is a string. :)

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Cory Kimble

I want to get string from textbox and write to RFID device formatted in HEX "## ## ## ## ## ## ## ## ## ## ## ##" so, my goal is to (i think) convert text into Ascii then into hex and then I can save into the format. Then I want to read from RFID and convert back to the Text. So I think I take formatted hex and convert to hex number and then to ascii number then to Text. I am getting screwed up on the steps. I think this will do the Write.

Dim i As Integer
Dim x As Integer
'Create array
Dim bytearray(23) As String
For i = 0 To bytearray.Length - 1
bytearray(i) = "0"
Next

 Dim hex As String
 Dim text As String = ""
 'Change Text into ASCII
 hex = Strings.Asc(TextBox1.Text)
 'Change Ascii into HEx
 hex = Long.Parse(hex, Globalization.NumberStyles.HexNumber)
 x = 0
 'Put hex into Format
 For i = hex.Length - 1 To 0 Step -1
 bytearray((bytearray.Length - 1) - x) = hex.Substring(i, 1)
 x += 1
 Next
 'Create full formatted string to write to RFID
 If TextBox1.Text<> "" Then
 For i = 0 To bytearray.Length - 1 Step 2
 text = text + bytearray(i) + bytearray(i + 1) + " "
 Next
 text = text.Substring(0, text.Length - 1)

If "f" is typed in text box then text variable should say "00 00 00 00 00 00 00 00 00 00 02 58" I need help converting that back to "f" I can get it back down to 258 which I think is the hex. I need to know how to convert back to Ascii and then Text. Any ideas? Text

I can't think of anything cool and nerdy to say.

Luc Pattyn

Hi, AFAIK this is completely wrong. 1. it does not work at all for more than one character since Strings.Asc(string) only looks at the first character of the string. 2. the conversion for a single character does not work (well, it does convert, but in a nonsensical way) The simple example where original text is "f", it is an ASCII character with numeric value 102 in decimal, which is 66 in hex. Indeed the outcome of Strings.Asc(TextBox1.Text) is the number 102 ERROR1: you erroneously store that in the string variable named "hex" which now holds "102" ERROR2: then you parse, i.e. decode, it as if it were a hex number, hence the result is the number 258 since 1*256+0*16+2*1 equals 258. ERROR3: you again erroneously store that in the string variable named "hex" which now holds "258" and finally you do a lot of moving around to get some zeroes and spaces What you probably want is something along these lines:

Sub rfid2()
    Dim maxChars As Integer = 12
    Dim Text As String = "ABC123   f"
    Console.WriteLine("Encoding """ & Text & """ in " & maxChars & " hex chars")

    Dim length As Integer = Text.Length
    Dim result As String = ""
    Dim i As Integer

    For i = 1 To maxChars - length
        result = "00 " & result
    Next

    For i = 0 To length - 1
        Dim chr As Integer = Strings.Asc(text.Substring(i, 1))
        result = result & chr.ToString("X2") & " "
    Next
    Console.WriteLine("result=" + result)
End Sub

This generates "00 00 41 42 43 31 32 33 20 20 20 66 " where each of the characters is clearly visible in hex. :)

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Cory Kimble

Ok, that works, but how do I take the ASCII and display the text?

I can't think of anything cool and nerdy to say.

Luc Pattyn

Hi, To reverse the process, you need to perform the reverse of the same steps, in reverse order. AFAIK the reverse of Strings.Asc is Strings.Chr, and the reverse of int16.ToString("X2") is int16.Parse() where you will want the right NumberStyle. I leave the details for you to work out. :)

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Cory Kimble

Got it! Thank you.

I can't think of anything cool and nerdy to say.