Subject:
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Re: IR Tower
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 23 Dec 1998 07:17:42 GMT
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Original-From:
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Peter Hesketh <pbh@phesk.demon.co.IHATESPAMuk>
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Viewed:
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1748 times
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In article <dbaum-2212981930170001@pm3-6-12.chi-focal.enteract.com>,
Dave Baum <lugnet.robotics@lugnet.com> writes
> I think there's also some sort of AGC on the
> pre-amp which is why tranmissions are always balanced (same number of 0's
> and 1's).
I have come across this statement (balanced 0's and 1's) several times
but it is not quite true. It would be true if the RS232 frame was 8
data and no parity, but AIUI the RCX uses odd parity. This means that
there will be times when a sequence of bytes is sent which all contain
the parity bit set to a 1. Admittedly this only unbalances the signal
by one part in eleven*, but it is still an imbalance.
(* 8 data + 1 start bit + 1 stop bit + 1 parity bit = 11)
--
Regards - Peter Hesketh, Mynyddbach, Mon.
Forty reasons why a dog is better than a woman: number 14
"If a dog is gorgeous, other dogs don't hate it."
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Message has 1 Reply:
 | | Re: IR Tower
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| (...) Right you are - but EE's often ignore effects less than 10% in calculations :-) I was referring to the practice of formatting the data such that a byte is always followed by its complement (except for the first part of a sync which is 0x55). (...) (26 years ago, 24-Dec-98, to lugnet.robotics)
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Message is in Reply To:
| | Re: IR Tower
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| (...) Almost nothing. Tx is just the TXD signal gated to send the 38kHz carrier. It also ties into a timer circuit for the auto-shutoff. Rx is a little more complicated - a filter/amp/comparator system to detect the presence of 38kHz IR. I think (...) (26 years ago, 23-Dec-98, to lugnet.robotics)
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