[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

*Subject*: Re: [amsat-bb] CRC*From*: Dquagliana@xxxxxxx*Date*: Sun, 3 Jun 2001 23:11:21 EDT

In a message dated 01-06-02 11:25:08 EDT, you write: > > Could someone give me a reference /discussion on the meaning of CRC'c > referenced for the data content of AO-40 Telemetry? thanks, Farrell Winder, > W8ZCF. The CRC is a Cyclic Redundancy Check. It's a way of verifying that you received what the sender sent. This is done using a set of mathematical operations that takes as input the bytes you are sending and outputs a "CRC" residue. The sender computes and sends this, and the receiver also computes it. If they match, then you probably received what they sent (with a high but not 100% probability). Ok, I've greatly simplified, but this is the basic idea. It's actually a bit more complicated. The AMSAT CRC as used on AO-40 is based on the polynomial x^16 + x^12 + x^5 + 1. More details are available on Amsat's web site at: http://www.amsat-dl.org/p3d/tlmspec.txt in section 7. If you're really interested in CRC math, the calculations, the various CRC-16's, CRC-32, and computing lookup tables, I suggest "C Programmers Guide to NetBIOS" by David Schwaderer. (Yes, it's a NETBIOS book, but the back quarter or so of the book is all about CRC's.) Hope this helps, Douglas KA2UPW dquagliana@aol.com ---- Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA. To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

- Prev by Date:
**Re: Discussion Level,** - Next by Date:
**AIDC 3733's for sale** - Prev by thread:
**Re: Discussion Level,** - Next by thread:
**Re: CRC** - Index(es):