different crc32 result from crccalc.com/

[Brandonn-Etheve]

Running included crc32 example sketch on an arduino uno i get:

/home/brd/Arduino/libraries/CRC/examples/CRC32_test/CRC32_test.ino
89A1897F
89A1897F
89A1897F
CDBAC17A
18

while https://crccalc.com/ with "123456789" input: ascii, output: hex, i get: 0xCBF43926

here the crccalc result link

What i'm missing?

[RobTillaart]

I'll have a look
...

Got the same results as you (so it is at least consistent)
CRC32_test.ino
89A1897F
89A1897F
89A1897F
CDBAC17A
18

These are the settings, these are NOT in the table at crccalc.com

void CRC32::reset()
{
  _polynome   = CRC32_DEFAULT_POLYNOME;  (== 0x04C11DB7)
  _startMask  = 0;
  _endMask    = 0;
  _crc        = 0;
  _reverseIn  = false;
  _reverseOut = false;
  _started    = false;
  _count      = 0;
}

Checking with - http://zorc.breitbandkatze.de/crc.html
and values seems OK.

Think you missed the XOR with 0xFFFFFF at the end (in the crccalc table)

[RobTillaart]

CDBAC17A is the CRC-32 when adding the string 123456789 twice.

[Brandonn-Etheve]

Thanks for your time.
since there was a comment in the example sketch : // Serial.println("Verified with - https://crccalc.com/\n");
i though that the default setting should match the output of that website.

Using:
crc.setPolynome(0x04C11DB7);
crc.setStartXOR(0xFFFFFFFF);
crc.setEndXOR(0xFFFFFFFF);
crc.setReverseIn(true);
crc.setReverseOut(true);

the output is CBF43926 as expected.
since many website use those setting (including https://crc32.online/ and other) maybe you should use it as default setting, or add the link to http://zorc.breitbandkatze.de/crc.html instead of https://crccalc.com in the sketch comment.
Anyways issue solved.

[RobTillaart]

Good point to use at least a setting that is in the table.
I'll make a note of it for a next release to improve the examples.

Might be useful to have a dump() function to print all settings at once. => easier to check them.

[RobTillaart]

FYI triggered by your question I created a 0.2.0 version

• Added getters for the parameters in the CRC classes so they become easier to verify programmatically.
• Reduced the calls to yield() in add(array, length) to improve performance.
  now one in every 256 additions yield is called()..
• minor edits.