Module cadu 

Channel Access Data Unit — ASM framing and frame sync (CCSDS 131.0-B-5). Channel Access Data Unit (CADU) — TM Synchronization and Channel Coding

Spec: CCSDS 131.0-B-5 (TM Synchronization and Channel Coding)

A CADU is the unit produced by the Coding & Synchronization sublayer on the downlink (TM/AOS direction). It consists of:

┌──────────┬────────────────────────┐
│  ASM     │  Transfer Frame        │
│ (4 bytes)│  (fixed-length)        │
└──────────┴────────────────────────┘

The Attached Sync Marker (ASM) is a fixed 32-bit pattern that the receiver uses to locate frame boundaries in the continuous bitstream. The standard ASM for TM/AOS is 0x1ACFFC1D.

Proximity-1 uses a 24-bit ASM (0xFAF320) as defined in CCSDS 211.2-B-3.

This module provides:

• ASM constants for TM, AOS, and Proximity-1
• CADU encoding (prepend ASM to a frame)
• Frame synchronization (find ASM in a bitstream)

Structs

AsmDeframer

ASM deframer implementing Deframer.

AsmFramer

ASM framer implementing Framer.

AsmWriter

Wraps an PhysicalWrite to prepend an ASM before writing.

FrameIter

Iterator over frames found by FrameSync::find_all_frames.

FrameSync

A frame synchronizer that searches for ASM patterns in a byte stream to locate frame boundaries.

FrameSyncReader

Wraps an PhysicalRead to find and strip ASM from incoming data.

Enums

AsmWriterError

Errors from ASM writer operations.

CaduError

Errors that can occur during CADU operations.

FrameSyncReaderError

Errors from frame sync reader operations.

Constants

ASM_PROXIMITY1

24-bit ASM for Proximity-1 links (CCSDS 211.2-B-3).

ASM_TM

Standard 32-bit ASM for TM and AOS frames (CCSDS 131.0-B-5).

ASM_TM_INVERTED

Inverted 32-bit ASM used for the odd frames when Convolutional coding with ambiguity resolution is employed.

Functions

decode_cadu

Strips the ASM from a CADU and returns the frame payload.

encode_cadu

Encodes a transfer frame into a CADU by prepending the ASM.