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Further CRC problems

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I have posted before regarding my difficulties computing a CRC. At this point I have made a test program based on a VI downloaded from another thread on this forum. I've made some modifications to it, in order to be able to set poly, reflections etc. from outside the VI.

 

I have come to use an parametrized model for defining CRC algorithms, as described in this document: http://www.ross.net/crc/download/crc_v3.txt . According to this model my algorithm should be described

 

Name   : "X-25"
Width  : 16
Poly   : 1021
Init   : FFFF
RefIn  : True
RefOut : True
XorOut : FFFF
Check  : 906E

 

This description was given to me by someone at another forum, focused on computer interfacing. He came up with the name X-25, as far as I know it doesn't have anything specifically to do with that protocol (It should be used with a Philips patient monitor, which has it's own protocol, but appearently it has simillairities with X-25). The 'Check' is

The value you are suppoused to get when you run the ASCII-string '123456789' through the algorithm.

 

My questions: As far as I can see, this doesn't work. I've been trying it on some examples of sniffed communication and on the test string, and none of it gets a correct value. The test program allows you to set the parameters of the algorithms differently, but I haven't found another combination that works either. So at this point I want to rule out that there is a built in error in the CRC-computing VI itself. Any ideas?

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"Abs_CRC_Test" is the main test program, it lets you set the parameters ("absolute CRC" is another word for "parametrized model CRC").

"Absolute_CRC" is the CRC-algorithm itself.

"Escape" removes escape characters from a frame

"ReflectByte" reflects a byte... : )

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From the attached archive extract the CRC16_Calculator.vi. The pic shows you how to setup the parameters.

 

Setup for CRC Calculation 

Message Edited by waldemar.hersacher on 02-02-2009 06:13 PM
Waldemar

Using 7.1.1, 8.5.1, 8.6.1, 2009 on XP and RT
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I have recently seen the other thread about CRC and made some checks.

 

The archive contains some of the VIs you have found and were provided in the other thread. Unfortunatly the VI you need is not part of the archive. So I attach the VI here.

Message Edited by waldemar.hersacher on 02-02-2009 08:19 PM
Waldemar

Using 7.1.1, 8.5.1, 8.6.1, 2009 on XP and RT
Don't forget to give Kudos to good answers and/or questions
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I can't read the files in the archive, they are for an old version (I use LabVIEW 8.5). The CRC16_Calculator.vi is working excellently, though.

 

Thank you very much.

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Hi Tzench.  I am also writing code to communicate with the Philips Intellivue Patient Monitor.  Might be interesting to chat.  Let me know if you're interested.

http://www.medicollector.com
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Hi,

 

In the next few days I'll receive an Intellivue Monitor and I'll write some code to communicate with the equipment.

 

PM me you are you interested in some sort of cooperation that could ease both our tasks.

 

Let me know.

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You do realize that you are asking for help in a 2 year old thread from someone who hasn't been back on the forums in the last 2 years. You might be better off starting a new thread.



Mark Yedinak
Certified LabVIEW Architect
LabVIEW Champion

"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot
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Mark,

 

josborne posted a few days back, so in my humble opinion this is a live thread and it could be a way to get in touch as he doesn't have private messaging enable. Thanks

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