Examples

>>> '%X' % CRC32.calcString('123456789')
'CBF43926'

This test function runs all of the defined algorithms on the test input string '123456789':

>>> _printResults()
CRC-5-USB: 19
CRC-8-SMBUS: F4
CRC-15: 059E
CRC-16: BB3D
CRC-16-USB: B4C8
CRC-CCITT: 29B1
CRC-HDLC: 906E
CRC-24: 21CF02
CRC-32: CBF43926
CRC-32C: E3069283
CRC-64: 46A5A9388A5BEFFE
CRC-256: 79B96BDC0C519B239BE759EC0688C86FD25A3F4DF1E7F054AD1F923D0739DAC8

Calculating in parts:

>>> value = CRC32.calcString('1234')
>>> '%X' % CRC32.calcString('56789', value)
'CBF43926'

Or, done a different way:

>>> crc = CrcRegister(CRC32)
>>> crc.takeString('1234')
>>> crc.takeString('56789')
>>> '%X' % crc.getFinalValue()
'CBF43926'

Inversion of a CRC function:

>>> CRC_CCITT.reverse().reflect().calcWord(54321, 16, 0)
1648
>>> CRC_CCITT.calcWord(_, 16, 0)
54321

A 15-bit CRC is used in CAN protocols. The following sample CAN frame (in binary here) is converted to hexadecimal for the calcWord call. The bits after the 15-bit CRC are not included in the CRC:

0 11101000001 0 0 0 0001 00010010 011000010111011 1 1 1 1111111

This sample CAN frame was found in this paper: <http://www.anthony-marino.com/documents/HDL_implementation_CAN.pdf>

>>> '%X' % CRC15.calcWord(0x3A08112, 27)
'30BB'

If the CRC is included, the remainder should always be zero:

>>> print CRC15.calcWord(0x1D0408930BB, 42)
0

A 5-bit CRC is used some kinds of USB packets. Here is a sample start-of-frame packet:

10100101 01100111000 01111

(found at <http://www.nital.com/corporate/usb2snooper.html>)

The first field is the PID (not included in the CRC), the next 11-bit field is the frame number (0xE6, LSb-first order), and the final five bits are the CRC (0x1E, LSb-first order).

>>> '%X' % CRC5_USB.calcWord(0xE6, 11)
'1E'