Subject:
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Re: Lego Network Protocol questions
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 6 May 1999 11:03:45 GMT
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Original-From:
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Ben Laurie <ben@^antispam^algroup.co.uk>
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Viewed:
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875 times
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Kekoa Proudfoot wrote:
> Regarding detecting collisions, I forgot to mention that you can only
> detect a collision after an entire byte has been transmitted. This is a
> pain, since every collision costs you at least one byte time. This affects
> algorithms that try to avoid further collisions by waiting a random delay
> before retransmitting. I think this makes slotted algorithms look more
> attractive.
I'd've thought that collision detection would not be hugely reliable,
anyway - I'd guess that your own signal would drown out anything else.
This is a completely untested assumption, though!
> > The clock shows up because the transitions always happen on a clock tick,
> > hence the wire-line signal embodies some notion of time that can be used
> > to synchronize both ends.
>
> I think something like this is possible on the H8. You might be able to
> use the rhythm established by the reception of bytes from other RCXs to
> keep clocks in sync, although the timings would be somewhat coarse grained
> and you'd have to leave space for whatever the margin of error ended up
> being.
I'm not sure why you think the timing would be coarse? It only has to be
fine enough to get you down to the bit level (meaning you waste around
10% of the available bandwidth in avoiding overlap), and most UARTs
sample 16 times per bit, so that should be easy...
Cheers,
Ben.
--
http://www.apache-ssl.org/ben.html
"My grandfather once told me that there are two kinds of people: those
who work and those who take the credit. He told me to try to be in the
first group; there was less competition there."
- Indira Gandhi
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message has 1 Reply:
 | | Re: Lego Network Protocol questions
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| (...) This is a possibility I hadn't considered, and it sounds reasonable to expect to see that effect at some point. I never tested how a second source affects echo reception, but it seems easy enough to test. If I get around to testing this I'll (...) (25 years ago, 6-May-99, to lugnet.robotics)
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