Subject:
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Re: RCX comunications - UDP/IP???
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 5 Dec 2002 04:29:33 GMT
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Original-From:
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Steve Baker <sjbaker1@airmail.#nospam#net>
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Viewed:
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822 times
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Jeff Wood wrote:
> Is the RCX capable of broadcasting a message without handshaking similar to
> UDP/IP using NQC? For those that arent familar, UDP simply broadcast a
> packet and doesn't require a confirmation that the packet was recieved
> unlike its brother TCP/IP
THe simple 'SendMessage(c)' command in NQC doesn't do any handshaking
- and (of course) it broadcasts.
> This is for a race car on the discussion that I would like the car to
> broadcast an Identifier, lap time or otherwise for "pit board" type
> communications between the multiple cars and a separate RCX trackside.
THe 'SendMessage' command only sends a single byte - and one problem
with this is that if you want to send a multi-byte message, it may
be only partially recieved.
There are also problems if multiple RCX's send data at the same time -
the results will be horribly mangled and probably rejected by the
computer that's reading them.
This would make sending something complex quite difficult - but it's
certainly not impossible. You just need to be sure that some of the
bits out of every byte you send identify what part of the message this
is - and who it's from.
> any code example would be great.
The NQC documentation for SendMessage/ClearMessage/Message is
quite clear. I don't think you'll need an example.
However, I have some code that sends and recieves messages here:
http://www.sjbaker.org/steve/lego/master_slave/
You may want to consider a 'master/slave' setup where the
trackside computer polls cars as they break an optical beam at
the start/finish line. That way you can be reasonably certain
that you'll be in a position to hear their reply - and by telling
each car in turn to report, you can prevent them from all talking
at once - which eliminates one cause of data corruption.
---------------------------- Steve Baker -------------------------
HomeEmail: <sjbaker1@airmail.net> WorkEmail: <sjbaker@link.com>
HomePage : http://web2.airmail.net/sjbaker1
Projects : http://plib.sf.net http://tuxaqfh.sf.net
http://tuxkart.sf.net http://prettypoly.sf.net
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Message is in Reply To:
 | | RCX comunications - UDP/IP???
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| Is the RCX capable of broadcasting a message without handshaking similar to UDP/IP using NQC? For those that arent familar, UDP simply broadcast a packet and doesn't require a confirmation that the packet was recieved unlike its brother TCP/IP This (...) (22 years ago, 5-Dec-02, to lugnet.robotics)
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