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<H1 ALIGN=CENTER>Analog Button-Box Interface for Arduino</H1>
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<A HREF="index.htm">HOME</A>&nbsp;&gt;&nbsp;<A HREF="make.htm">Creative Technology</A>&nbsp;&gt;&nbsp;<B>Analog Buttons</B>
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This design is useful to interface a number of push-button switches with
a single analog input pin on a microcontroller such as the
<A HREF="http://www.arduino.cc">Arduino</A>.
It's different from the many digital multiplexer or shift-register
schemes that are used with microcontrollers, because it's analog,
uses just a few resistors, and connects to an analog input pin.
The usual methods require an additional chip, usually either a
<A HREF="http://en.wikipedia.org/wiki/Multiplexer" TITLE="Wikipedia: Multiplexer">multiplexer</A>
or a parallel-in
<A HREF="http://en.wikipedia.org/wiki/Shift_register" TITLE="Wikipedia: Shift register">shift register</A>.
The analog method has the limitation that you can't detect multiple,
simultaneous button presses.
But that doesn't make it useless &mdash; in fact, many personal
stereos (Mini-disk and MP3) use this method to connect the playback
controls to the stereo.
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<IMG SRC="reschain_bb.png" WIDTH=263 HEIGHT=189 ALT="Analog Button-Box Breadboard">
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...
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<H2>Links</H2>
<A HREF="http://llg.cubic.org/tools/sonyrm/">Sony RM-X2S XMMS driver</A>, which shows
the use of a Sony RM-X2S car radio remote control. This type of wired remote control
is a resistive button-box, just like we have described on this page.
The linked page containes a pinout for the 3.5mm jack plug on the
remote, as well as resistance values for the various controls.
The controls are all those normally associated with a car radio, such
as volume, mute, tuning and input selection.
A secondhand RM-X2S control unit could be re-purposed for use with a
microcontroller as a generic input device.
The RM-X3S and RM-X4S are newer versions, but with different labels on the controls.
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