| Author |
Message |
Snamprogetti
New User
Joined: 17 Apr 2009
Posts: 3
Location: Italia
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| Apr 17, 2009 1:59 pm |
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Hello, i can't get an UPS device to accept my CRC values.
The specs say: standard CRC-CCITT 16 bit, 1021h polynom, 554Dh initial value. I tried many algorithms with these specs, but i never get what the device wants. I know it wants for example:
data 20 22 52 53 30 30 -> CRC 9087h
Thanks for any help |
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regregex
Preferred Member
Joined: 30 Oct 2007
Posts: 119
Location: London, UK
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| Apr 17, 2009 5:28 pm |
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Hello Snamprogetti, welcome to the forum.
The documentation is correct, except the initial vector has already been reversed to match the CRC-CCITT algorithm which shifts right instead of left. In Rocksoft™ notation it would be: | Code: | Width : 16
Poly : 1021
Init : B2AA
RefIn : True
RefOut : True
XorOut : 0000
Check : 63D0 |
(For an explanation of this record, see A Painless Guide to CRC Error Detection Algorithms by Ross Williams.)
(For a generic implementation in C, see A Painless Guide or the Calculator page.)
Also, could you please tell me the make and model of the UPS so I can add this algo to my catalogue?
HTH
--Greg |
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Snamprogetti
New User
Joined: 17 Apr 2009
Posts: 3
Location: Italia
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| Apr 20, 2009 9:16 am |
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Thank you. It is a Dialog by Riello.
I solved because they sent me their own source code.
Actually all other algorithms i've tried (i haven't tried lammertbies.nl's one though) don't give that result even using B2AA (see zorc.breitbandkatze.de/crc.html for example) |
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Snamprogetti
New User
Joined: 17 Apr 2009
Posts: 3
Location: Italia
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| Apr 20, 2009 9:21 am |
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| Sorry last example works but you also have to reverse data bytes and CRC result. |
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regregex
Preferred Member
Joined: 30 Oct 2007
Posts: 119
Location: London, UK
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| Apr 20, 2009 11:54 am |
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Thank you for the reference.
--Greg |
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