manual/plugins/alpinecdc.tex

   1 \subsection{Alpine CD changer emulator}
   2 This plugin emulates an Alpine CD changer. It allows to plug the Archos to a
   3 compatible head unit and control the playback from there, too. Currently
   4 implemented is track change, shuffle, seek, but no disk change. The plugin is a
   5 TSR, meaning it silently operates in the background once started. It will keep
   6 doing so until a new plugin is started.
   7 Alpine also did M-Bus as OEM for other brands (Honda, Acura, Volvo, BMW, etc.)
   8 Nowadays Alpine uses a different protocol, called Ai-Net, not supported by this
   9 plugin. (As well as all other protocols, please do not ask for such!)
  10
  11 \subsubsection{The cable}
  12 Hookup to Archos works by connecting the headphone output including the remote
  13 pin (you need a 4-ring 3.5 mm plug for that) to the changer jack of the radio.
  14 M-Bus radios have a DIN-style circular jack with 8 pins (7 in a $\sim$ 270 degree
  15 circle, one in the center). A standard 5-pin DIN plug is OK for this, since we
  16 do not use the other (power) pins.
  17
  18 As OEM, they shuffled the pins around a bit, better check first if it is not
  19 genuine Alpine. The bus pin is pulled high to 12 volts with a $\sim$ 2kOhm resistor,
  20 pulses driven low. Because it is open collector, this is not harmful to the
  21 Archos.\\
  22 ASCII art of the 4-pin headphone plug:
  23 \begin{verbatim}
  24 / \
  25 \_/ left    -> Alpine pin 5
  26 |_| right   -> Alpine pin 4
  27 |_| remote  -> Alpine pin 1
  28 |_| ground  -> Alpine pin 2 + 3
  29 \end{verbatim}
  30
  31 The remote pin can be programmed bidirectional, that is the reason this works.
  32 Very luckily the M-Bus uses a single wire communication and the two radios I
  33 tried are happy with the 3.3 Volt level the Arcos can deliver. So the
  34 connection is a simple cable! For all protocols requiring more lines, an
  35 external controller would be necessary.
  36
  37 \note{Archos FMs do not have the remote pin internally connected, but
  38   one unit that was opened was internally prepared for it, a matter of closing a
  39   bridge.}