Subject:
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Re: IR transmission, strange coding ?
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Tue, 6 Nov 2001 20:19:48 GMT
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Viewed:
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4710 times
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hi Kekoa,
thanks for your answer,
About the strange stop bit, I was wrong (John Barnes also mailed me about that,
thanks John) it was indeed the parity bit. About the startbit (which is
inverted to the data) I'm (almost) absolutly sure, I measured it with a scope
and I programmed it in that way in my "remote-tower"control and it works. But
maybe both methods work, so will try that later this evening and let you know
the results.
best regards,
Stef Mientki
Kekoa Proudfoot wrote:
> Stef Mientki <s.mientki@ids.kun.nl> wrote:
> > According to what Kekoa Proudfoot found
> > "A '0' is coded as a 417us pulse of 38kHz IR, a '1' bit is
> > 417us of nothing."
> > ok, nothing wrong with that.
>
> I forget exactly how I measured this. I think maybe I hooked a scope
> directly to the LEDs then sent a constant stream of something to the tower
> and looked at the waveform on the scope. I don't remember noticing
> anything funny with the start and stop bits, but I don't remember looking
> either, so something fishy like you described might be going on.
>
> On the other hand, my assumption has always been that the circuitry in the
> tower is pretty simple, that the tower does no interpretation of the data,
> and that therefore the start and stop bits are coded just the same as all
> other bits.
>
> Thinking about this more, I can't see the tower examining the data to tweak
> the encoding of the start and stop bits. There are some things we got to
> work that would not have worked if the tower did this. In particular, we
> got the tower to transmit at a 2x baud rate just fine. If the tower
> adjusts the start and stop bits, I'm pretty sure it would have screwed up
> the 2x baud rate.
>
> -Kekoa
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Message is in Reply To:
 | | Re: IR transmission, strange coding ?
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| (...) I forget exactly how I measured this. I think maybe I hooked a scope directly to the LEDs then sent a constant stream of something to the tower and looked at the waveform on the scope. I don't remember noticing anything funny with the start (...) (25 years ago, 6-Nov-01, to lugnet.robotics.rcx)
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