[avr-libc-dev] [bug #45067] inconsistency & errors in crc.h documentation

[anonymous]

URL:
  <http://savannah.nongnu.org/bugs/?45067>

                 Summary: inconsistency & errors in crc.h documentation
                 Project: AVR C Runtime Library
            Submitted by: None
            Submitted on: Sun 10 May 2015 05:59:16 PM UTC
                Category: Documentation
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Documentation
                  Status: None
        Percent Complete: 0%
             Assigned to: None
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 1.8.0
           Fixed Release: None

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Details:

>From http://www.nongnu.org/avr-libc/user-manual/group__util__crc.html:

"Optimized CRC-XMODEM calculation.
x^16 + x^12 + x^5 + 1 (0x1021)"

The hex representation of the poly is correct, but doesn't match the long
form, which should be:
x^16 + x^15 + x^5 + 1

Other parts of the docs give the reversed poly in hex instead of the actual
poly:
"Optimized Dallas (now Maxim) iButton 8-bit CRC calculation.
Polynomial: x^8 + x^5 + x^4 + 1 (0x8C)"

It would be better to describe them the way pycrc does, with the actual poly
used and whether or not the crc reflects (reverses) the bits.
https://www.tty1.net/pycrc/crc-models_en.html





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