GLAST LICOS Current Value Table subpackage

Introduction

This sub package contains a set of python classes for support of and access to the LICOS Current Value Table (CVT)

Definitions and Acronyms

• CV Current Value (object)
• CVT current value table (object)
• CCSDS A NASA data transfer protocol
• VSC The Virtual SpaceCraft interface
• observer A client that "observes" a CV. When a CV is updated, each observer is notified of the update asynchronously.
• requestor A client that "requests" a CV. This request is synchronous.

TCP protocol

All messages are based on a simple TCP protocol.

• Messages are INT16-strings: strings preceded with a 16 bit ushort length
  Note: This gives an inherent limit to the length of a message of 64k.
• Messages to the server are in plain text and are of the format <keyword> [<arguments>]
• Messages from the server are typically binary strings with a 3 character keyword prepending. Ex; "up ........." indicates an update of a CV of some sort.

Files and Applications

• CurrValServer.py Implements the base current value table service and protocol as well as a server for testing
  (Classes CurrentValueFactory, CurrentValueProtocol)
  
  Usage: python CurrValServer.py --pktFile packet.out --cvtPort 39800

• CurrValClient.py Implements the base current value table client (observer protocol) as well as a base client for testing
  (Classes CurrValClientFactory, CurrValClient)
  
  Usage: python CurrValClient.py --cvtHost localhost --cvtPort 39800

• CvtTesterImpl.py Implements a test CVT client (observer protocol) to display individual telemetry values with engineering unit conversions.
  
  Usage: python CvtTesterImpl.py --cvtHost localhost --cvtPort 39800 --pktList "LHKADAB33V,LHKADABTEMP"

• ScriptClient.py Implements the base current value table client (requestor protocol) as well as a base client for testing
  (Classes ScriptClient)
  
  Usage: python ScriptClient.py --cvtHost localhost --cvtPort 39800

• VscCvt.py Implements the connection of the CVT to the VSC/spacecraft
  The file vsc.cfg is in LICOS_ETC and is a template
  Usage: python VscCvt.py --vscHost lat-elf2 --config vsc.cfg

Classes

CurrentValueFactory

CurrentValueProtocol

CurrValClientFactory

CurrValClient

ScriptClient

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