Is SHCOARSE (in example) assumed to be the beginning of the user data field?

[haisamido]

I'm fairly new to this module so pardon my rudimentary question. In the below example, is SHCOARSE assumed to be the beginning of the user data field, i.e. after primary and secondary headers?

pkt = ccsdspy.FixedLength([
  PacketField(name='SHCOARSE', data_type='uint', bit_length=32),
  PacketField(name='SHFINE',   data_type='uint', bit_length=20),
  PacketField(name='OPMODE',   data_type='uint', bit_length=3),
  PacketField(name='SPACER',   data_type='fill', bit_length=1),
  PacketField(name='VOLTAGE',  data_type='int',  bit_length=8),
....
])

[ddasilva]

No problem @haisamido, long time no chat (I think we chatted on the NASA slack a few times a long time ago).
In this example SHCOARSE is the first field to parse after the primary header. Let me know if that answers your question.

[haisamido]

Thank you for your answer. Long time indeed @ddasilva :-). What if one wanted to also capture header metadata as separate telemetered parameters, such as:

  PacketField(name='packet_version_number', data_type='uint', bit_length=3 ),
...
  PacketField(name='packet_data_length', data_type='uint', bit_length=16),

I ask this because this is a nominal feature, where I work, where one can query the packet_version_number, and any of the header metadata, such as, packet_type, secondary_header_flag, etc.

[ddasilva]

Of course! With FixedLength.load() and VariableLength.load(), you can pass a keyword argument called include_primary_header=True to get the primary header fields back in the result dictionary.

The names of the primary header fields it adds to the dictionary are:
CCSDS_VERSION_NUMBER, CCSDS_PACKET_TYPE, CCSDS_SECONDARY_FLAG, CCSDS_APID, CCSDS_SEQUENCE_FLAG, CCSDS_SEQUENCE_COUNT, and CCSDS_PACKET_LENGTH

There is also a shortcut function ccsdspy.utils.read_primary_headers(file) if you don't care about also parsing the body of the packet.

[haisamido]

Excellent! Thank you.