Subject:
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Re: Speed of IR comms?
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 2 Oct 2002 22:53:48 GMT
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Original-From:
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Steve Baker <(sjbaker1@airmail)ihatespam(.net)>
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Reply-To:
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SJBAKER1@AIRMAILsaynotospam.NET
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Viewed:
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693 times
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Laszlo Meszaros (ETH) wrote:
> My notebook and my mobile phone can communicate to each other
> with approximately 1 mbits per second, over an infrared link.
> Do you have any experience with speeding up the computer-RCX
> communication...?
Bad news I'm afraid:
Your laptop and phone are using IrDA which is a vastly different
technology than the RCX uses. The RCX protocol is more like a
TV remote. (In fact, if you have a 'learning' remote, you can
use it to drive your RCX!)
I vaguely recall someone reporting that they'd cranked the baud
rate on both tower and RCX up to 9600 baud (I believe the default
is 1200 baud) - but that's still more than 100 times slower than
your cellphone/laptop.
Worse still is the problem of bi-directional communications. The
RCX/PC comms protocol imposes heavy delay penalties when you switch
from transmitting to receiving and vice-versa.
I presume the reason for this is that the IrDA specification only
guarantees it to work over about a meter - (although in practice, you
can sometimes get much longer ranges). Clearly that's not enough for
the RCX - so something slower but with greater range was chosen.
----------------------------- Steve Baker -------------------------------
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Message has 2 Replies:
 | | Re: Speed of IR comms?
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| ----- Original Message ----- From: "Steve Baker" <sjbaker1@airmail.net> Sent: Wednesday, October 02, 2002 6:53 PM Subject: Re: Speed of IR comms? (...) LEGO and CIR (Consumer Infra-Red) send signals on a modulated carrier frequency (36KHz, 38KHz, or (...) (22 years ago, 3-Oct-02, to lugnet.robotics)
| | | Re: Speed of IR comms?
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| (...) FYI. The RCX normally runs at 2400 baud, but it is effectively 1200 baud because the protocol sends every byte twice. Markus and I were able to get downloads to run at a true 4800 baud by downloading a short program to hack some registers and (...) (22 years ago, 4-Oct-02, to lugnet.robotics)
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