Subject:
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Re: RCX Communications.
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 11 Jan 2000 21:39:59 GMT
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Viewed:
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894 times
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In lugnet.robotics, Russell Nelson <nelson@crynwr.com> writes:
> Paul Frost writes:
> > I am considering building a PIC based remote control for the RCX, & I am
> > slightly confused by your communications details.
> >
> > Can you confirm that a '0' bit is transmitted as 417uS 38kHz IR & '1' as
> > 417uS of nothing. This seems back to front to me, unless the 38kHz IR is
> > continuously transmitted. In the abscence of any IR, the RCX would appear • to
> > receive a continuous stream of 0xff characters. With '1' transmitted as no
> > IR, it would seem difficult to reliably detect the start bit.
It helps (indeed is critical), to remember that the serial you see over
a RS232 'wire', is electrically the inverse of the 'logic', so the wire
goes high, when at logic '0', and low when at logic '1'. The description
of the actual transmission protocols with regards to signalling is spot
on.
The fault in the web page is only in the actual data format used. I
allready have a PIC program that will probably do what Mr Frost wants.
You can generate a suitable serial stream, by simply taking a normal RS232,
and feeding it through a resistor and a 'clamp' diode to keep the signal
levels between 0 and 5v, into one input of a 'NAND' gate. Feed the other input
with a 38kHz tone (anything between about 25kHz and 60kHz will actually work),
The output will go high whenever the LED should be driven (emitter follower
gives the required drive).
Best Wishes
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Message is in Reply To:
 | | Re: RCX Communications.
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| Paul Frost writes: > I am considering building a PIC based remote control for the RCX, & I am > slightly confused by your communications details. > > Can you confirm that a '0' bit is transmitted as 417uS 38kHz IR & '1' as > 417uS of nothing. This (...) (25 years ago, 11-Jan-00, to lugnet.robotics)
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