GetPacket

1
Task flow chart
PacketReceived Queue
GetPacket
TimeDelayed Array
Send Acknowledge
Command Switch Statement
NextTime
ArrayIndex
OSTimeDelay
2
GetPacket Explained

• Get packet checks received packet queue to see if
  there is a packet. If there is a packet it is
  pulled off the queue and an acknowledge packet is
  sent
• Get packet then checks a NextTimeStamp variable
  to see if there is a packet in the TimeDelayed
  queue that needs serviced
• If the timestamp in the time delayed queue is
  before a packet just received from the received
  queue, then the received packet is stuffed in the
  time delay queue. The packet that needed service
  in the time delay queue is then passed to the
  switch statement to be processed.
• If there is no packet in the time delayed queue
  (the NextTimeStamp is set to null) or the
  received packets timestamp is before the one in
  the time delay queue then the received packet is
  passed to the switch statement to process
• Get packet waits for the next packet to process
  in one of two ways
• No packets in the time delay queue If there are
  no packets in the time delay queue then task
  pends on the received queue until a packet is
  received indefinitely
• Packet in the time delay queue If there are
  packets in the time delay queue but they dont
  need serviced yet, then the task pends on the
  received queue for X amount of time. If no
  packet is received in that time, then get packet
  checks the time delay queue to see if there is a
  packet that needs service. (Note this time
  could be calculated for when the next packet in
  the time delay queue needs service so that the
  task doesnt run again until a packet needs
  serviced)

3
Questions about command parse

• Are we getting send/receive functions from the
  packet send/receive team or are we working
  directly with the input queue?
• On commands should we set a max time for
  completion? Meaning that if a command wants our
  task to do the work instead of spawning a new
  task, do we define a processing time limit?
• Who parses the data? We are working on specifying
  format for commands but do we actually parse the
  data or pass each command a generic payload that
  they parse
• I am leaning towards the latter that way if the
  parameters for a command change then only that
  commands code needs to change rather than that
  command and the code in the command parse
• Should the acknowledge be sent before or after
  the command is actually serviced? I think it
  should be before because commands may take a
  while to service and the ground station will have
  no way of knowing if the packet was even received.