CONTEXT : Using GNURADIO I saved AIS vessel information in file Ra

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Invalid checksum for HDLC Frame about crc HOT 2 CLOSED

nicoretti commented on July 28, 2024

Invalid checksum for HDLC Frame

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Comments (2)

Nicoretti commented on July 28, 2024

Hi @FranckN-maker,

thanks for reporting. Apparently the snippet below works just fine.

from crc import Configuration, Register

config = Configuration(
    width=16,
    polynomial =0x1021,
    init_value=0xffff,
    final_xor_value=0xffff,
    reverse_input=False,
    reverse_output=False,
)

reg = Register(config)

expected = 0x1B18
data = [18, 65, 116, 210, 22, 0, 0, 245, 121, 26, 250, 44, 48, 41, 135, 240, 127, 165, 123, 0, 96]

reg.init()
reg.update(data)

assert expected == reg.digest()

That said, it looks like you have found a bug in the convenience wrapper Calculator.

from crc import Configuration, Calculator

config = Configuration(
    width=16,
    polynomial =0x1021,
    init_value=0xffff,
    final_xor_value=0xffff,
    reverse_input=False,
    reverse_output=False,
)

calc = Calculator(config)

expected = 0x1B18
data = [18, 65, 116, 210, 22, 0, 0, 245, 121, 26, 250, 44, 48, 41, 135, 240, 127, 165, 123, 0, 96]

assert expected == calculator.checksum(data)

yields the wrong checksum.

Recommendation

Until #113 have been fixed, I recommend you use the register API (TablesBasedRegister, Register).

best
Nico

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Nicoretti commented on July 28, 2024

Issue is closed, because the underlying problem is now tracked in #113.
If the provided recommendation is not sufficient or not leading to a resolution, please reopen the issue.

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