File ccsds_core.h¶

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CCSDS 131.0-B's published literals, as a Python-facing component. More...

#include "clib_common.h"

Public Functions¶

Type	Name
void	asm_bits (uint8_t * out) The CCSDS Attached Sync Marker, 0x1ACFFC1D, as 32 unpacked bits.

Detailed Description¶

The values one standard picked, kept BESIDE the general layer rather than inside it. ccsds_tm (native/inc/ccsds_tm/ccsds_tm.h) is where those picks are defined and certified; this component is the thin face that carries them to Python, and holds no arithmetic of its own.

This is deliberately NOT a binding of ccsds_tm's transforms, and must not become one. The outer code, the randomiser and the inner code are reached by DESCRIBING a CADU through doppler.wfm.FrameDesc — the general assembler runs the standard's kernels from an ops table, which is what keeps wfm/wfm_frame.h free of CCSDS. See docs/design/frame-description.md.

Public Functions Documentation¶

function asm_bits¶

The CCSDS Attached Sync Marker, 0x1ACFFC1D, as 32 unpacked bits.

void asm_bits (
    uint8_t * out
)

out[0] is the first bit on the wire — figure 9-1 of 131.0-B numbers the marker's bit 0 as the most significant bit of 0x1A. One bit per byte, the convention every frame path here passes around.

The thing a Python receiver ACQUIRES on: pair it with doppler.detection.SyncFinder to find where a CADU starts in a bit stream, then slice and Frame.check() it. The marker is deliberately NOT randomised (10.4's NOTE: "The ASM was not randomized and is not derandomized"), so it reads the same in every frame and in exactly one polarity — which is what makes it the only thing in a CADU that can report a 180-degree carrier ambiguity.

A function rather than a constant a caller expands, because an MSB-first expansion written out twice is a transcription that can disagree with itself. This tree's own doctests were the second copy until doppler#900, and this alias exists so the third copy is not a Python one: it delegates to ccsds_tm_asm_bits, which is where the expansion is written and where test_ccsds_tm_asm holds it to the published pattern.

Parameters:

out Receives 32 bits, one per byte.

>>> from doppler.ccsds import asm_bits
>>> b = asm_bits()
>>> b.size, b[:8].tolist()          # 0x1A, first bit at the top
(32, [0, 0, 0, 1, 1, 0, 1, 0])
>>> int("".join(map(str, b.tolist())), 2) == 0x1ACFFC1D
True

The documentation for this class was generated from the following file native/inc/ccsds/ccsds_core.h