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
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.
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 www.pueblo.gsa.org 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)
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-51 | Rita-51J
| Design Philosophy | RitaBrowser
| NetApi51 | Example
| Ping Utility