crc

Overview ¶

Package crc provides CRC checksums used across CCSDS standards.

The normative authority for these algorithms is the CCSDS Blue Books that specify each Frame/Packet Error Control Field:

• CCSDS 133.0-B-2 clause 4.1.4 (Space Packet Protocol, Packet Error Control)
• CCSDS 132.0-B-3 clause 4.1.6 (TM Space Data Link, Frame Error Control Field)
• CCSDS 232.0-B-4 clause 4.1.4 (TC Space Data Link, Frame Error Control Field)
• CCSDS 732.0-B-4 clause 4.1.6 (AOS Space Data Link, Frame Error Control Field)
• CCSDS 732.1-B-3 clause 4.1.6 (USLP, 16-bit Frame Error Control Field)
• CCSDS 211.2-B-3 annex C (Proximity-1 coding, 32-bit CRC)

The Green Book CCSDS 130.0-G-4 (Overview of Space Communications Protocols) is informative background only.

CRC-16-CCITT: generator polynomial x^16 + x^12 + x^5 + 1 (0x1021), initial value 0xFFFF, no reflection, no final XOR. Check value: CRC("123456789") = 0x29B1.

CRC-32: generator polynomial x^32 + x^23 + x^21 + x^11 + x^2 + 1 (0x00A00805, MSB-first), the Proximity-1 CRC-32 of CCSDS 211.2-B-3 annex C: the register is preset to zero (unlike the CRC-16, which presets to all ones) with no reflection and no final XOR. The retired first issue of USLP (CCSDS 732.1-B-1, 2018) borrowed it for an optional 32-bit FECF; that option was removed in 732.1-B-2, and current USLP (732.1-B-3 clause 4.1.6.2.2) carries only the 16-bit FECF. This is NOT the IEEE CRC-32 (0x04C11DB7) and NOT CRC-32C/Castagnoli (0x1EDC6F41). Check value: CRC("123456789") = 0x51693C0C.