e2022a26d0
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@11967 a1c6a512-1295-4272-9138-f99709370657
39 lines
1.9 KiB
TeX
39 lines
1.9 KiB
TeX
\subsection{Alpine CD changer emulator}
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This plugin emulates an Alpine CD changer. It allows to plug the Archos to a
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compatible head unit and control the playback from there, too. Currently
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implemented is track change, shuffle, seek, but no disk change. The plugin is a
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TSR, meaning it silently operates in the background once started. It will keep
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doing so until a new plugin is started.
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Alpine also did M-Bus as OEM for other brands (Honda, Acura, Volvo, BMW, etc.)
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Nowadays Alpine uses a different protocol, called Ai-Net, not supported by this
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plugin. (As well as all other protocols, please do not ask for such!)
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\subsubsection{The cable}
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Hookup to Archos works by connecting the headphone output including the remote
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pin (you need a 4-ring 3.5 mm plug for that) to the changer jack of the radio.
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M-Bus radios have a DIN-style circular jack with 8 pins (7 in a $\sim$ 270 degree
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circle, one in the center). A standard 5-pin DIN plug is OK for this, since we
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don't use the other (power) pins.
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As OEM, they shuffled the pins around a bit, better check first if it's not
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genuine Alpine. The bus pin is pulled high to 12 volts with a $\sim$ 2kOhm resistor,
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pulses driven low. Because it's open collector, this is not harmful to the
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Archos.\\
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ASCII art of the 4-pin headphone plug:
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\begin{verbatim}
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/ \
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\_/ left -> Alpine pin 5
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|_| right -> Alpine pin 4
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|_| remote -> Alpine pin 1
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|_| ground -> Alpine pin 2 + 3
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\end{verbatim}
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The remote pin can be programmed bidirectional, that's the reason this works.
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Very luckily the M-Bus uses a single wire communication and the two radios I
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tried are happy with the 3.3 Volt level the Arcos can deliver. So the
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connection is a simple cable! For all protocols requiring more lines, an
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external controller would be necessary.
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\note{Archos FMs don't have the remote pin internally connected, but
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one unit that was opened was internally prepared for it, a matter of closing a
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bridge.}
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