Package org.yamcs.tctm.pus

Class PusPacketPreprocessor

  • All Implemented Interfaces:
    PacketPreprocessor
    public class PusPacketPreprocessor
extends AbstractPacketPreprocessor
    Implementation for ECSS PUS (ECSS-E-ST-70-41C) packets. The header structure is:

    Primary header (specified by CCSDS 133.0-B-1)

    • packet version number (3 bits)
    • packet type (1 bit)
    • secondary header flag (1 bit)
    • application process ID (11 bits)
    • sequence flags (2 bits)
    • packet sequence count (14 bits)

    Secondary header (PUS specific)

    • TM packet PUS version number (4 bits)
    • spacecraft time reference status (4 bits)
    • service type ID (8 bits)
    • message subtype ID (8 bits)
    • message type counter (16 bits)
    • destination ID (16 bits)
    • time (absolute time) variable
    • spare optional

    The time packets have no secondary header and the apid set to 0. The data part consists of the current onboard time in the same encoding like in the normal packets.

    In this class we read

    • the APID and sequence count from the CCSDS primary header interested in the time and the sequence count.
    • the time from the PUS secondary header and from the time packets.

    The offset of where the time is read from is configurable as this has changed between different versions of the standards.

    Example configuration: 

     dataLinks:
 ...
 - name: tm_realtime
   packetPreprocessorClassName: org.yamcs.tctm.pus.PusPacketPreprocessor
   packetPreprocessorArgs:
   errorDetection:
     type: CRC-16-CCIIT
   pktTimeOffset: 13
   timePktTimeOffset: 7
   timeEncoding:
      epoch: CUSTOM
      epochUTC: 1970-01-01T00:00:00Z
      timeIncludesLeapSeconds: false

    • Constructor Detail

      • PusPacketPreprocessor

        public PusPacketPreprocessor​(String yamcsInstance)

      • PusPacketPreprocessor

        public PusPacketPreprocessor​(String yamcsInstance,
                             YConfiguration config)

    • Method Detail

      • process

        public TmPacket process​(TmPacket tmPacket)
        Description copied from interface: PacketPreprocessor
        Processes the packet and returns it.

        What this function does is project depended. However, we expect that the generation time and sequence count are filled in.

        Can return null if the packet is to be ignored.

        Parameters:
        tmPacket - - the packet that has to be processed
        Returns:
        the processed packet