Plug and Play Technology for SpaceWire: Drivers and Alternatives

Authors: 
Peter Mendham, Steve Parkes, Stuart Mills, Chris McClements
Conference/Journal Name: 
58th IAC (International Astronautical Congress)
Date Published: 
September 2007

SpaceWire has proved very successful since the release of the standard by ECSS.   This success is due to the versatility of SpaceWire and its inherent simplicity and low implementation cost.  Beyond the requirement for each packet to be lead by an address and terminated by an end-of-packet marker, SpaceWire does not specify the contents of each packet.  The proposed SpaceWire Protocol Identifier standard (currently in draft) provides a method for SpaceWire packets to carry higher-layer protocols. The Remote Memory Access Protocol (RMAP) has been proposed (also in draft) as has the possibility of a protocol to support Plug and Play on SpaceWire networks.   

This paper begins by discussing the driving requirements behind Plug and Play, specifically examining the potential benefits that a Plug and Play protocol could bring to SpaceWire systems.  These benefits are further examined in practical scenarios, debating the relevance of plug and play features to space-based systems.  The paper argues that the most important feature of a plug and play system for space-based SpaceWire networks is that of network discovery.  The next part of the paper examines network discovery in some detail, discussing the relative merits of different algorithms and key features of their implementation.  Prototype software, intended to demonstrate the network discovery process, is presented along with results and analysis.

 A full implementation of plug and play poses certain challenges to existing SpaceWire hardware, such as the ESA standard router which was developed by the University of Dundee.  The paper examines what key plug and play features can be deployed over existing hardware, using the University of Dundee router as a case study.