Solved

CRC Calculator Implementation in VB.NET

Posted on 2007-11-26
7
5,172 Views
Last Modified: 2012-08-14
So I kind of need an CRC check in my code that i have written (I am reading stuff from serial).  I want to be able to send an integer (or even better a byte() ), and then return the 16-CRC for that.  I kind of have a vague recollection of how CRC works, but from whatI remember I have to break things down by bits.  Is that even possible in .NET?  Please provide me with as much info on doing this task as possible.  If there is a class already implemented somewhere online (open source of course), that would work as well.  It has to be something that I can integrate with my code though.
0
Comment
Question by:feldmani
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 3
7 Comments
 
LVL 8

Expert Comment

by:Thejaka
ID: 20355348
There are various crc algorithms. For information regarding some of these, try http://en.wikipedia.org/wiki/Cyclic_redundancy_check

For an implementation in C#, try http://www.codeproject.com/csharp/marcelcrcencoding.asp

I did a particular implementation in C# sometime back, but first, you have to pick your algorithm!
0
 
LVL 1

Author Comment

by:feldmani
ID: 20355523
Unfortunately I need VB.NET, not C#.  I know I need CRC16 since that is what the motes are using.  I already looked through the wiki for this, didn't find anything that immediately looked helpful.
0
 
LVL 1

Author Comment

by:feldmani
ID: 20355526
I see what you are saying about the CRC16 having different versions.  Let me calculate and see which one I have.
0
Business Impact of IT Communications

What are the business impacts of how well businesses communicate during an IT incident? Targeting, speed, and transparency all matter. Find out more in this infographic.

 
LVL 1

Author Comment

by:feldmani
ID: 20411932
CRC-16-CCITT Is the type I need.  Sorry for the delay in the response.
0
 
LVL 8

Expert Comment

by:Thejaka
ID: 20416923
I don't believe I have the code of an implementation of that algorithm with me at the moment, but there are several existing implementations publicly  available on the web.

Below is the implementation of the algorithm found at http://www.sanity-free.org/133/crc_16_ccitt_in_csharp.html converted from C# to VB.NET.

I guess you can use it as a starting point and adapt it to your needs.

NOTE: I haven't taken the time to verify the operation of the original implementation, simply translated it to VB.NET. Anyhow, if you have any trouble with this, let me know.

Also, depending on your requirements, it may be possible to implement the algorithm as a single function.
0
 
LVL 8

Accepted Solution

by:
Thejaka earned 500 total points
ID: 20416960
Original: http://www.sanity-free.org/133/crc_16_ccitt_in_csharp.html

Translated to VB.NET.

Imports System
 
Public Enum InitialCrcValue
  Zeros
  NonZero1 = 65535
  NonZero2 = 7439
End Enum
 
Public Class Crc16Ccitt
  Const poly As UShort = 4129
  Private table As UShort() = New UShort(255) {}
  Private initialValue As UShort = 0
 
  Public Function ComputeChecksum(ByVal bytes As Byte()) As UShort
    Dim crc As UShort = Me.initialValue
    For i As Integer = 0 To bytes.Length - 1
      crc = CUShort(((crc << 8) Xor table(((crc >> 8) Xor (255 And bytes(i))))))
    Next
    Return crc
  End Function
 
  Public Function ComputeChecksumBytes(ByVal bytes As Byte()) As Byte()
    Dim crc As UShort = ComputeChecksum(bytes)
    Return New Byte() {CByte((crc >> 8)), CByte((crc And 255))}
  End Function
 
  Public Sub New(ByVal initialValue As InitialCrcValue)
    Me.initialValue = CUShort(initialValue)
    Dim temp As UShort, a As UShort
    For i As Integer = 0 To table.Length - 1
      temp = 0
      a = CUShort((i << 8))
      For j As Integer = 0 To 7
        If ((temp Xor a) And 32768) <> 0 Then
          temp = CUShort(((temp << 1) Xor poly))
        Else
          temp <<= 1
        End If
        a <<= 1
      Next
      table(i) = temp
    Next
  End Sub
End Class

Open in new window

0
 
LVL 1

Author Comment

by:feldmani
ID: 20422783
Thanks,  Let me try playing with this and see if I am getting the right answer.  Greatly appreciated.
0

Featured Post

Free Tool: Path Explorer

An intuitive utility to help find the CSS path to UI elements on a webpage. These paths are used frequently in a variety of front-end development and QA automation tasks.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Wouldn’t it be nice if you could test whether an element is contained in an array by using a Contains method just like the one available on List objects? Wouldn’t it be good if you could write code like this? (CODE) In .NET 3.5, this is possible…
Real-time is more about the business, not the technology. In day-to-day life, to make real-time decisions like buying or investing, business needs the latest information(e.g. Gold Rate/Stock Rate). Unlike traditional days, you need not wait for a fe…
This video shows how to use Hyena, from SystemTools Software, to update 100 user accounts from an external text file. View in 1080p for best video quality.

734 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question