Package org.yamcs.tctm.ccsds

Class DownlinkTransferFrame

java.lang.Object
org.yamcs.tctm.ccsds.DownlinkTransferFrame
Direct Known Subclasses:
AosTransferFrame, TmTransferFrame, UslpTransferFrame
public abstract class DownlinkTransferFrame extends Object
Transfer frame is an interface covering the three CCSDS transfer frames types:
  • TM (CCSDS 132.0-B-2)
  • AOS (CCSDS 732.0-B-3)
  • UNIFIED ( 732.1-B-1)

All three of them have the following structure:

  • Primary Header
  • Insert Zone/Secondary Header
  • Data Field
  • Operational Control Field (OCF)
  • Error Control Field

Note that for USLP, the data field has also a header.

In the dataStart, and dataLength properties below, only the real data (i.e. excluding the data field header) is considered.

The idea is that the VcDownlinkHandler that deals with the data, has to have all the information on how to interpret the data part.

For the purpose of packet extraction each frame has defined three offsets:
dataStart <= firstSduStart < dataEnd

firstSduStart refers to the first SDU that starts in this frame.

The data in between dataStart and firstSduStart is part of a previous packet and will be used only if there is no discontinuity in the frame sequence count.

  • Field Details

    • spacecraftId

      protected final int spacecraftId

    • virtualChannelId

      protected final int virtualChannelId

    • data

      protected final byte[] data

  • Constructor Details

    • DownlinkTransferFrame

      public DownlinkTransferFrame(byte[] data, int spacecraftId, int virtualChannelId)

  • Method Details

    • getSpacecraftId

      public int getSpacecraftId()
      Returns:
      master channel id

    • getVirtualChannelId

      public int getVirtualChannelId()
      Returns:
      virtual channel id

    • lostFramesCount

      public int lostFramesCount(long prevFrameSeq)
      Returns the number of frames lost from the previous sequence to this one. If no frame has been lost (i.e. if prevFrameSeq and getFrameSeq() are in order) then return 0. -1 means that a number of lost frames could not be determined - if there is some indication that the stream has been reset
      Parameters:
      prevFrameSeq -
      Returns:

    • setVcFrameSeq

      public void setVcFrameSeq(long seq)
      Set the virtual channel frame count
      Parameters:
      seq -

    • getVcFrameSeq

      public long getVcFrameSeq()
      Returns:
      virtual channel frame count

    • getData

      public byte[] getData()

    • getDataStart

      public int getDataStart()
      Where in the byte array returned by getData() starts the data.
      Returns:

    • getFirstHeaderPointer

      public int getFirstHeaderPointer()
      Where in the byte array returned by getData() starts the first packet (assuming this is a frame containing packets). Returns -1 if there is no packet starting in this frame.
      Returns:
      the offset of the first packet that starts in this frame or -1 if no packet starts in this frame

    • getDataEnd

      public int getDataEnd()
      The offset in the buffer where the data ends.
      Returns:
      data end

    • setOcf

      public void setOcf(int ocf)

    • getOcf

      public int getOcf()
      Get the 4 bytes operational control field. This has a meaningful value only if the hasOcf() returns true.
      Returns:
      the Operational Control Field.

    • hasOcf

      public boolean hasOcf()
      Returns:
      true if this frame has an Operation Control Field set.

    • getEarthRceptionTime

      public Instant getEarthRceptionTime()
      Returns:
      the earth reception time of the frame

    • setEearthRceptionTime

      public void setEearthRceptionTime(Instant ertime)