Subject:
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Re: RCX controlling minidisc player
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Tue, 16 Jan 2001 03:19:07 GMT
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Viewed:
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1681 times
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> I am the owner of a minidisc player and thought that it would be cool to
> have the RCX control it and tell it what to play. Most minidisc players can
> use a wired remote, which is a little device which allows you to control
I was about to write a reply to your question when, as I was removing
some of the quotes, I read the part about your minidisk player having
a "wired" remote. "Wired"?! Do they still make home electronics with
remotes connected by wire? I haven't seen that in years. I just wanted
to be sure we were talking about the same thing. Infra-red remotes are
everywhere (and probably cheaper than the cable) these days. Are you
sure that's not what you are referring to? Anyway, my answer...
CONTROLLER UNIT
I/O PORT A I/O PORT B
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X---X---X----X-------|-----|-----|-----|----[resistor]---- +
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X---X---X----X-------------|-----|-----|----[resistor]---- +
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X---X---X----X-------------------|-----|----[resistor]---- +
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X---X---X----X-------------------------|----[resistor]---- +
This is how most keypads are wired (one variation or another). When
you press a key (X) you are connecting the output of PORTA on the
controller to the input of PORTB. The controller strobes (sends breif
signals) out on portA and looks for them to appear at one of PORTB's
inputs. The combination of strobe signals and corresponding inputs
tells the controller which of the (in this case) 16 keys was pressed.
It's never a good idea to have the input to a controller not connected
to any electrical point (which would be the case when the switches are
not being pressed) and so [resistor]'s are added (usually called
"pull-up" resistors) to keep the input at a known voltage level when
the keys are not being pressed.
This is not to say that it couldn't be done the way you described
with different values of resistors connected to each swtich and these
pairs arranged in parallel. It's actually the basis of some D/A
(digital-to-analog) converters, but it requires:
A) Accurate resistance values - especially if there are many
keys. If the resistance values deviate too much from their ideal
value, the controller might not read it as the proper key.
B) Resistance values selected so that each value cannot be
duplicated by a combination of other values. If they were, it would be
possible to press two or more keys and get the same function of a
different key, just because the combined resistance values associated
with the two or more keys turns out to be the same as that of another
key and will cause the controller to respond to a key that isn't being
pressed.
C) Converting from an analog format which is what you are
describing to a digital format use the by the minidisks controller -
and you can be 99.99% sure that there's a digital controller in there.
Why would a manufacturer do the conversion if the above diagram is
entirely digital to begin with? It would just be an extra expense and
complication. The A/D converter this would require would still have to
connect to the controller's input and output ports anyway.
Your idea can be implemented with a 4016 Quad Bi-lateral Switch. This
is a chip with 4 two-directional switches, each controlled by an input
pin. The switch outputs would go across the switches of the remote and
the input pin would be driven by the RCX.
Matthias Jetleb
VA3-MWJ
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Message has 1 Reply:
 | | Re: RCX controlling minidisc player
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| (...) Yes, it seems a lot of Minidisc players do anyway. (...) This really is how they do it. If you go here you can see the schematic for a Sony remote: (URL) go here and scroll down to the section titled "Portable's Remote Control Interface", you (...) (24 years ago, 16-Jan-01, to lugnet.robotics.rcx)
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Message is in Reply To:
| | RCX controlling minidisc player
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| Hello, I am the owner of a minidisc player and thought that it would be cool to have the RCX control it and tell it what to play. Most minidisc players can use a wired remote, which is a little device which allows you to control your player from a (...) (24 years ago, 16-Jan-01, to lugnet.robotics.rcx)
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