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Rockbox mail archiveSubject: ANNOUNCE: Rockbox emulates M-Bus car CD changer (Alpine and OEM)ANNOUNCE: Rockbox emulates M-Bus car CD changer (Alpine and OEM)
From: [IDC]Dragon <idc-dragon_at_gmx.de>
Date: Thu, 20 Nov 2003 13:01:58 +0100 (MET) Hello for a longer post, (quote wisely ;-) I'm proceeding to what I actually bought my Archos for: To be world's largest CD changer in my car, controlled by the radio. I have an older Alpine radio, which uses their "M-Bus" for the communication between radio and CD changer. For details, see my page: http://joerg.hohensohn.bei.t-online.de/mbus/index.htm Alpine also did this as OEM for other brands (Honda, Acura, Volvo, BMW, etc.) Nowadays Alpine uses a different protocol, called Ai-Net, not subject of this. (As well as all other protocols, please don't ask me for such!) Hookup to Archos works by connecting the headphone output including the remote pin (you need a 4-ring 3.5 mm plug for that) to the changer jack of the radio. M-Bus radios have a DIN-style circular jack with 8 pins (7 in a ~270 degree circle, one in the center). A standard 5-pin DIN plug is OK for us, since we don't use the other (power) pins. I have found an Alpine M-Bus pinout here: http://www.nsx.net/projects/alpine.html As OEM, they shuffled the pins around a bit, better check first if it's not genuine Alpine. The bus pin is pulled high to 12 volts with a ~2kOhm resistor, pulses driven low. Because it's open collector, this is not harmful to the Archos. And this is my ASCII art of the 4-pin headphone plug: (available in Germany from Reichelt for 1.95 EUR) _ / \ \_/ left -> Alpine pin 5 |_| right -> Alpine pin 4 |_| remote -> Alpine pin 1 _|_|_ ground -> Alpine pin 2 | | | | The remote pin can be programmed bidirectional, that's the reason this works. Very luckily the M-Bus uses a single wire communication and the two radios I tried are happy with the 3.3 Volt level the Arcos can deliver. So the connection is a simple cable! For all protocols requiring more lines, an external controller would be necessary. Archos FMs don't have the remote pin connected, but the one I looked into was internally prepared for it, a matter of closing a bridge, see: http://rockbox.haxx.se/mail/archive/rockbox-archive-2003-09/0599.shtml I have made a plugin which now is in shape for a first release. It emulates a changer such that the audio signal can be fed into the radio. The plugin contains all the M-Bus send and receive code, plus a "demo" emulation which follows all radio commands and keeps the communication alive. So you can change disks and tracks, play, pause, stop, FF/FR, etc., but this is a fake. You'll have to prepare your playback and volume beforehand, start the plugin when everything's running. My files are here, rocks for Recorder and Player, plus source: http://joerg.hohensohn.bei.t-online.de/archos/alpine_cdc/ I haven't added it to cvs since the use is probably too exotic. Plus, a plugin can't control the mp3 playback nor query play state information. This could be added, but then you still would need to start that plugin (unless we can get something like autorun a plugin or better a .cfg which calls a plugin) and can't use the box in the normal way. My current plan is to integrate the code into Rockbox (after 2.1 release) for a special build. So you'd have to decide what the remote pin will be used for: Archos remote or M-Bus. Happy cable soldering! Jörg -- NEU FÜR ALLE - GMX MediaCenter - für Fotos, Musik, Dateien... Fotoalbum, File Sharing, MMS, Multimedia-Gruß, GMX FotoService Jetzt kostenlos anmelden unter http://www.gmx.net +++ GMX - die erste Adresse für Mail, Message, More! +++Received on 2003-11-20 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |