The Philosophy and Systems Approach
Networking allows you to monitor and control nodes from afar.  It also allows you to use information from remote locations to take action elsewhere.  In control engineering, this is referred to “distributed control.”  In a private setting, you may want to check on your house, for instance, while you are on vacation.  In a more industrial setting, a greenhouse may contain smart irrigation and heating systems, which may be controlled from any where on the network: from the greenhouse, the office, or home.    

There are many communications protocols to network low-cost controllers (for example, RS-485 or CAN).  Most networking protocols require additional software drivers and in some cases, hardware, to be added to the PCs.  They may also implement custom or proprietary protocols.  In some applications, specific operator interfaces are needed.  All of these things add to the cost and development time.   

RITA uses the standard Internet communication protocols for networking.  The Internet is a very wide network; worldwide to be exact. The rapid spread and acceptance of the Internet has reduced the cost of its associated technologies.   RITA by using standard Internet protocols can tap into this worldwide network.  Moreover, the PCs and their operating systems natively support the related protocols.  For example, you may simply configure your PC to have a certain IP (internet protocol) address through the provided services of the operating system. Once you have an IP address anyone from anywhere on the network can communicate with you over the Internet.  The RITA node can also be assigned an IP address and placed on the Internet in a similar fashion.      

The Internet protocols are ideally suited for PC-to-PC communications.  The size and processing requirements of these protocols (TCP/IP) determine the size of the processor that runs the node.  In a typical application that implements the full TCP/IP suite, you may find an embedded 32-bit processor running a multi-tasking kernel.  Such embedded PCs are commonly used, but are expensive for simple low-cost implementations.  A typical embedded PC costs a few thousand Dollars per node, while RITA nodes reduce the cost by an order of magnitude, to a few hundred Dollars per node.

We would like both: to reduce the cost of controller nodes and to be able to communicate with the controller nodes over the Internet.  This requires a systems approach.  Clearly, a low cost (typically 8-bit) controller need not implement the full TCP/IP suite.  Moreover, there are intrinsic qualities of controller nodes that make the full TCP/IP suite unnecessary.  There is a difference between the server of, say and your garage door opener.  The Pueblo server may be serving hundreds of clients simultaneously.  In fact, this is why a multi-tasking operating system is convenient in this case.  For each client, the server simply starts a new instance of the program.  The garage door opener, on the other hand should not be accessed by more than one client at a time.  After all, a situation where one client asks the door to open, while the other asks it to close, is quite intolerable.  In addition, the amount of data transfer among RITA nodes is much less than a typical HTTP session, where larger files (pictures or bitmaps, for example) are sent.  

These and other technical issues (see “RITA Messages” ) suggest a different approach.  RITA uses simple text-based messages to communicate with the nodes.  Messages are kept short to fit in a single frame.  The nodes may be viewed and controlled by a text-based browser.  Rigel Corporation offers the RitaBrowser to interact with the nodes.  However, other UDP browsers are just as viable.  The source code of such a simple browser is available from Rigel Corporation.  Situations that require graphical user interfaces may use a simple plug-in to display the information in standard Internet browsers. 

RITA  |  Rita-51  |  Rita-51J  |  Design Philosophy  |  RitaBrowser  |  NetApi51  |  ExamplePing UtilityNetCat



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