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hello everyone,
first of all, because I couldn'st search in the forum that's why I am opening this topic .. so if it exist already, let me know and Ill delete this topic.
I am told to build communication network among controllers. Coumputers could also be included, but if then in future, so computer inclusion is not that important right now maybe next section.
can anyone write his/her experience about using CAN or RS485 or XML as communication protocol ? which one is better and why ? any practical example schematic/project must be fully explained?
regards.
"I couldn'st search in the forum"
Why couldn't you?
There's a 'Search' box at the top-right of the page!
When you get your results to your initial search using that, there's a link for Advanced search - where you can refine your query.
It's not rocket science!
CAN defines both physical and protocol "layers" of a widely-used networking standard http://www.canopen.org
RS485 is merely a physical interface - it has nothing to do with any higher-level protocol that might happen to use that interface www.national.com/.../RS-485.html
XML is a text-based language used by a number of applications - it has nothing to do with networking or protocols. http://www.xml.org
Think of it like TCP/IP:
You can run TCP/IP over many different physical interfaces; eg, Serial; Dial-up modem; ADSL (Broadband); Ethernet; Wireless...
You can transport many different types of content over over a TCP/IP link; eg, e-mail; web pages; skype; files... (in fact, these each add their own protols "on top of" TCP/IP)
<quote> Think of it like TCP/IP: </quote>
i m not being told for tcp/ip !!!!!!!!!
Where did you find any information that this forum was expected to support block quotes using the tags you specified.
Then return to this text line: "Think of it like TCP/IP". Read that line again, and again. Notice the little word "like" in the sentence.
<bold> i dont <deep> LIKE </deep> this forum </bold>
i go and try another and see if they can help
<bold> i now delete the toipic <bold>
Well, there really are formatting available on this forum.
You first have to decide what physical layer to use.
RS485 or CAN requires special hardware. RS232 is more readily available. Questions you first have to ask is (partial list): - simplex/duplex transfers - topology: point-to-point, bus, tree, chain, ... - maximum cable length - required bandwidth - the cost for the physical layer - use of existing cables - amount of processor load to get required bandwidth - ...
If you know what physical layer to use, it is possible to decide what protocol to use. The choice of protocol is greatly affected by the physical carrier - or you would have to spend time to tunnel the information, in case you use a physical layer that isn't suited for the selected protocol. CAN for example only transmits tiny packets.
Since XML is just a way of formatting information, you can use XML together with RS485. XML together with CAN would result in a lot of work creating the tunneling layer.
Strictly speaking, you can use ppp and tunnel TCP/IP on RS485 links too, but the required amount of code is normally too high.