.. _library_ccsds_frames:

``ccsds_frames``
================

The ``ccsds_frames`` library provides support for CCSDS transfer frames.
The current implementation includes CCSDS telemetry transfer frames and
CCSDS telecommand transfer frames, plus CCSDS advanced orbiting systems
transfer frames, all using fixed frame lengths and optional
mission-profile fields configured at the object level.

API documentation
-----------------

Open the
`../../apis/library_index.html#ccsds_frames <../../apis/library_index.html#ccsds_frames>`__
link in a web browser.

Loading
-------

To load all entities in this library, load the ``loader.lgt`` file:

::

   | ?- logtalk_load(ccsds_frames(loader)).

Testing
-------

To test this library predicates, load the ``tester.lgt`` file:

::

   | ?- logtalk_load(ccsds_frames(tester)).

Available entities
------------------

- ``ccsds_frame_protocol`` Common protocol for transfer frame format
  objects.

- ``ccsds_frames`` Facade object for introspecting frame terms and
  bridging raw frame data fields with CCSDS space packets.

- ``ccsds_tm_frames(FrameLength, SecondaryHeaderLength, HasFECF)``
  Parametric object implementing parsing, generation, and accessors for
  CCSDS telemetry transfer frames.

- ``ccsds_tc_frames(FrameLength, SegmentHeaderLength, HasFECF)``
  Parametric object implementing parsing, generation, and accessors for
  CCSDS telecommand transfer frames.

- ``ccsds_aos_frames(FrameLength, InsertZoneLength, HasOCF, HasFECF)``
  Parametric object implementing parsing, generation, and accessors for
  CCSDS advanced orbiting systems transfer frames.

- ``ccsds_frames_types`` Type definitions for TM, TC, and AOS transfer
  frame byte encodings and terms.

Representation
--------------

Telemetry transfer frames are represented using the compound term:

::

   tm_transfer_frame(
       Version,
       SpacecraftId,
       VirtualChannelId,
       OCFFlag,
       MasterChannelFrameCount,
       VirtualChannelFrameCount,
       SecondaryHeaderFlag,
       SynchronizationFlag,
       PacketOrderFlag,
       SegmentLengthIdentifier,
       FirstHeaderPointer,
       SecondaryHeader,
       DataField,
       OCF,
       FECF
   )

Where:

- ``SecondaryHeader`` is either ``none`` or ``secondary_header(Bytes)``
- ``OCF`` is either ``none`` or ``ocf(Bytes)``
- ``FECF`` is either ``none`` or ``fecf(Bytes)``

Telecommand transfer frames are represented using the compound term:

tc_transfer_frame( Version, BypassFlag, ControlCommandFlag,
SpacecraftId, VirtualChannelId, SequenceNumber, SegmentHeader,
DataField, FECF )

Where:

- ``SegmentHeader`` is either ``none`` or ``segment_header(Bytes)``
- ``FECF`` is either ``none`` or ``fecf(Bytes)``

Advanced orbiting systems transfer frames are represented using the
compound term:

aos_transfer_frame( Version, SpacecraftId, VirtualChannelId,
VirtualChannelFrameCount, SignalingField, InsertZone, DataField, OCF,
FECF )

Where:

- ``SignalingField`` is
  ``signaling_field(ReplayFlag, FrameCountUsageFlag, SpacecraftIdExtension, FrameCountCycle)``
- ``InsertZone`` is either ``none`` or ``insert_zone(Bytes)``
- ``OCF`` is either ``none`` or ``ocf(Bytes)``
- ``FECF`` is either ``none`` or ``fecf(Bytes)``

Parsing and generating
----------------------

To parse a fixed 16-octet telemetry transfer frame without a telemetry
transfer frame secondary header and without a frame error control field:

::

   | ?- ccsds_tm_frames(16, 0, false)::parse(bytes([0x02, 0xA7, 0x10, 0x20, 0x18, 0x00, 1, 2, 3, 4, 5, 6, 0xDE, 0xAD, 0xBE, 0xEF]), Frames).

To generate the original byte sequence from the parsed term:

::

   | ?- ccsds_tm_frames(16, 0, false)::generate(bytes(Bytes), Frames).

To parse a fixed 10-octet telecommand transfer frame without a segment
header:

\| ?- ccsds_tc_frames(10, 0, true)::parse(bytes([0x20, 0x2A, 0x0C, 0x09,
0x07, 1, 2, 3, 0x44, 0x6D]), Frames).

To generate the original byte sequence from the parsed term:

\| ?- ccsds_tc_frames(10, 0, true)::generate(bytes(Bytes), Frames).

When FECF support is enabled for a frame object, parsing verifies the
incoming FECF, ``valid/1`` checks that it matches the remaining frame
fields, and ``generate/2-3`` recomputes it from the remaining frame
content. The parametric frame objects also provide ``update_fecf/2`` and
``verify_fecf/1`` for explicit integrity handling:

\| ?- ccsds_tc_frames(10, 0, true)::update_fecf(tc_transfer_frame(0, 1,
0, 42, 3, 7, none, [1,2,3], none), Frame).

\| ?- ccsds_tc_frames(10, 0, true)::verify_fecf(Frame).

To parse a fixed 12-octet AOS transfer frame without an insert zone,
OCF, or FECF:

\| ?- ccsds_aos_frames(12, 0, false, false)::parse(bytes([0x4A, 0x83,
0x12, 0x34, 0x56, 0x80, 1, 2, 3, 4, 5, 6]), Frames).

To generate the original byte sequence from the parsed term:

\| ?- ccsds_aos_frames(12, 0, false, false)::generate(bytes(Bytes),
Frames).

Types
-----

The ``ccsds_frames_types`` category defines the following types:

- ``ccsds_tm_frame(FrameLength, SecondaryHeaderLength, HasFECF)`` for
  byte encodings
- ``ccsds_tm_frame_term(FrameLength, SecondaryHeaderLength, HasFECF)``
  for frame terms
- ``ccsds_tc_frame(FrameLength, SegmentHeaderLength, HasFECF)`` for byte
  encodings
- ``ccsds_tc_frame_term(FrameLength, SegmentHeaderLength, HasFECF)`` for
  frame terms
- ``ccsds_aos_frame(FrameLength, InsertZoneLength, HasOCF, HasFECF)``
  for byte encodings
- ``ccsds_aos_frame_term(FrameLength, InsertZoneLength, HasOCF, HasFECF)``
  for frame terms

For example:

::

   | ?- type::check(ccsds_tm_frame(16, 0, false), [0x02, 0xA7, 0x10, 0x20, 0x18, 0x00, 1, 2, 3, 4, 5, 6, 0xDE, 0xAD, 0xBE, 0xEF]).

   | ?- type::check(ccsds_tm_frame_term(16, 0, false), tm_transfer_frame(0, 42, 3, 1, 16, 32, 0, 0, 0, 3, 0, none, [1,2,3,4,5,6], ocf([0xDE,0xAD,0xBE,0xEF]), none)).

   | ?- type::check(ccsds_tc_frame(10, 0, true), [0x20, 0x2A, 0x0C, 0x09, 0x07, 1, 2, 3, 0x44, 0x6D]).

   | ?- type::check(ccsds_tc_frame_term(10, 0, true), tc_transfer_frame(0, 1, 0, 42, 3, 7, none, [1,2,3], fecf([0x44,0x6D]))).

   | ?- type::check(ccsds_aos_frame(12, 0, false, false), [0x4A, 0x83, 0x12, 0x34, 0x56, 0x80, 1, 2, 3, 4, 5, 6]).

   | ?- type::check(ccsds_aos_frame_term(12, 0, false, false), aos_transfer_frame(1, 42, 3, 0x123456, signaling_field(1, 0, 0, 0), none, [1,2,3,4,5,6], none, none)).

Facade helpers
--------------

The ``ccsds_frames`` facade object provides generic accessors that work
across TM, TC, and AOS frame terms:

- ``frame_type/2``
- ``version/2``
- ``spacecraft_id/2``
- ``virtual_channel_id/2``
- ``data_field/2``
- ``ocf/2``
- ``fecf/2``
- ``update_fecf/2``
- ``verify_fecf/1``

It also provides raw payload bridge helpers for CCSDS space packets:

- ``extract_packets(Frame, SecondaryHeaderLength, Packets)`` parses the
  frame data field bytes using ``ccsds_packets(SecondaryHeaderLength)``.
- ``insert_packets(Packets, SecondaryHeaderLength, Frame, UpdatedFrame)``
  generates packet bytes using ``ccsds_packets(SecondaryHeaderLength)``
  and replaces the frame data field while leaving the remaining frame
  fields unchanged.

For example:

::

   | ?- ccsds_frames::extract_packets(tm_transfer_frame(0, 42, 3, 0, 16, 32, 0, 0, 0, 3, 0, none, [0x08,0x01,0xC0,0x00,0x00,0x03,0xDE,0xAD,0xBE,0xEF], none, none), 0, Packets).

   | ?- ccsds_frames::insert_packets([ccsds_packet(0, 0, 1, 1, 3, 0, none, [0xDE,0xAD,0xBE,0xEF])], 0, tm_transfer_frame(0, 42, 3, 0, 16, 32, 0, 0, 0, 3, 0, none, [], none, none), UpdatedFrame).

\| ?- ccsds_frames::update_fecf(tc_transfer_frame(0, 1, 0, 42, 3, 7,
none, [1,2,3], fecf([0x00,0x00])), UpdatedFrame).

\| ?- ccsds_frames::verify_fecf(UpdatedFrame).
