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Overview
   


BUSnet provides a cost-effective and robust communication network for switches, sensors and actuator applications.

BUSnet is an open standard, no royalties, licensing fees or costs for intellectual property. Creative Commons and/or GNU licenses will apply.

Some of the main features are...

Level 1 (physical)

  • Wide supply voltage, VBAT can range between 7 and 30 volts.
  • Currently uses RS-485 transceivers but other PHYs can be used or even mixed.
  • Redundant-ring or line wiring topology.
  • Bit rates fixed at 15200bps.
  • Nodes can be neatly daisy-chained.
  • Up to 1.2k (4000') between each node.

Level 2 (transport)

  • Implements a "publishing and subscribing" (AKA broadcast) model, nodes publish at will and subscribers act on the published data.
  • Multi-master, nodes can transmit at will.
  • High level of error detection (relative to the intended applications) for reliability, including frame-length field and CRC.
  • Can be used as is or as a transport mechanism for a higher-level protocol.
  • Plug-n-play, automatic allocation of addresses, no DIP switches.
  • Normal user frames with payloads up to 256 bytes.
  • 255 physical nodes each with an unlimited number of IO points.

Level 3 (application)

Note that Level 3 will be based on the old BUSnet protocol which was master/slave and will therefore have to be substantially modified. The points below are essentially a wish list at present.

  • High level of safety with “interlocks”, “feedbacks”, “timeouts”, security levels.
  • Points can read/display metric or imperial values.
  • Points report in engineering units.
  • Expandable, start with an single sensor node and a display node, then add features over time.

BUSnet is designed to be easy to develop for and easy to install, some of the design concepts are.

  • Standard wiring – BUSnet uses any 8-core cable. RJ45 modular jacks and Cat5/6 cables are preferred but anything can be used.
  • Standard async dataBUSnet uses standard asynchronous 8N1 serial protocol on the network.
  • Easy developmentBecause BUSnet uses standard async communications diagnostic equipment is kept to a minimum and really amounts to a simple logic analyser, oscilloscope, or serial analyser.

There are other networks around of course, but they have either too many features or too few. BUSnet is the following...

  • Open – Some of the existing networks are closed; you have to buy everything from the network vendor. Others are “open” but you have to pay $1000s to join the consortium or buy the spec. That’s not open to a hobbyist or even a small business. All BUSnet code and designs are available free of charge under Creative Commons or GNU licenses.
  • Simple – The BUSnet hardware is trivial, any electronics enthusiast can design for the network. The application-level software is also very simple and effectively amounts to interfacing with an I2C port.
  • Robust – Many simple networks have little or no protection from ESD, short circuits, open circuits etc. Some even connect processor MosFET inputs directly to the outside world. BUSnet uses RS-485 line drivers, a genuine industry standard that provides a very high level of protection and fault tolerance to the low-level hardware, high ESD protection and low EME. BUSnet also has safety features built into the protocol.
  • Small – Some existing networks require a huge amount of hardware even for a small node. I’ve seen one that needs about 9 square inches of PCB for the simplest node, while another needs 28 components. With BUSnet it is possible to build a functional (albeit very simple) node on a PCB about 12mm (½”) square using three active and three passive components.
  • Informal – Many networks require a system to be “designed” and “tuned” then “implemented”. Make changes and the process has to be repeated and in some cases processors even have to be re-flashed. BUSnet is very informal, you can start with a couple of nodes then add nodes as and when requirements or finances dictate. When the time comes just buy or build another node and plug it into the system.


   
 

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