DasTesnoAparat (or CarPi)

The aim is to find a better solution for car audio than the ancient CD player. By attaching a small Linux box into car's bus one could

1. emulate a very large, practically endless CD changer
2. view song and other data on the car's built-in display
3. browse through large quantities of songs (and other services) via a 2nd (larger) touch screen display

HW

• Raspberry Pi http://www.raspberrypi.org/

  • with a fast SD card for the OS. Might also store some MP3s there if there's enough space

• USB v6 adapter from http://www.reslers.de/IBUS/index.html to get access to the car's I-Bus

  • Reverse-engineered bus messages http://web.archive.org/web/20041204074622/www.openbmw.org/bus/

• A touch screen for more convenient usage (large playlists etc)
  • I prefer to keep the OEM look inside the car so there are 3 options:
    • Buy a used original 16/9 display, disassemble it and plant a new 7" screen inside it keeping just the frame and buttons
      • Capturing signals from the the original buttons around the display is a major pain but the outcome can be incredible

        • http://www.mp3car.com/hardware-development/139907-button-interface-to-bordmonitor-on-bmw-e39-and-e46-4.html#post1425437

        • http://www.mp3car.com/vbulletin/hardware-development/139907-button-interface-to-bordmonitor-on-bmw-e39-and-e46-4.html

    • Plant a new 7" screen inside a 2DIN radio bezel. This can be actually quite nice but is far from OEM-look
    • Keep the original CD player (with its small 1-line text display) as a "status" display and for more involving things attach a larger display to be kept hidden in the glove box or somewhere else
    • Actually, a cheap (used) tablet could be an option too
      • Its possible to embed one into a 2DIN radio bezel or place it somewhere else
      • The tablet could browse and control playlists over WLAN from the Pi
      • With some SW its possible to power up/shutdown a tablet automatically depending on if its charging or not
      • But are those things really robust enough to be mounted into the dashboard? I really wouldn't like to take the whole thing apart just to reset the tablet
  • Some components to think about

    • http://www.ebay.ie/itm/18cm-7-LCD-TOUCHSCREEN-AUTO-PC-MONITOR-12V-VGA-USB-/330682619123?pt=Auto_TFT_Monitore&hash=item4cfe3854f3

    • http://www.jimms.fi/tuote/TV-907D

    • http://www.jimms.fi/tuote/TV-908

    • http://www.cartft.com/catalog/il/1229

      • does Linux support USB displays?

    • http://www.cartft.com/catalog/il/442

• USB hard drive for MP3s, podcasts etc
• A nice box for the Pi
• Some future, nice-to-have kind of things:
  • 3G dongle for Internet access
    • Send an SMS when the car's alarm goes off?
    • With some relays controlling of motor and cabin heaters
  • BT dongle for streaming audio (A2DP) and calls from my cell phone

    • BlueZ has support for many BT profiles http://www.bluez.org/

  • USB or Bluetooth GPS dongle
    • Enables maps and navigation
  • USB Wifi stick

SW

• Fedora and Debian both support arm-linux

• XBMC http://www.raspbmc.com/

• Eventually Android if 256M is enough memory and a cheap resistive touch screen works

• I-Bus library for communicating over the bus http://projects.tevs.eu/OpenBM/wiki/Software/Gateway

  • There something here http://sourceforge.net/projects/ibusmp3/ from 2006, have to see if its usable

  • This looks much more promising http://projects.tevs.eu/OpenBM/wiki/Software/Gateway

• CDC emulator SW which actually will play the songs from a SD card or from a USB drive, will probably write this myself

The work plan

The order in which I'm going to do stuff is something like this:

• Once Pi arrives, install a distro and check that it works
• Then attach the I-Bus adapter and check that it is recognised by Linux
• Find/write the I-Bus library and try to get a "Hello World" text to the car's current, built-in radio display

• Write the CDC emulator SW. Now, we should be able to enjoy virtually endless music from numerous playlists

• Attack the display challenge, try to find a reasonable touch screen and make it work
  • If successful, install XBMC or some other media player environment
• Then install GPRS, GPS, BT, Wifi etc

Some random notes for myself

• It seems like touch screens output USB HID mouse events from the touch part?

  • http://www.youtube.com/watch?v=iGKqMJOoF-o

• To save energy, we need to power-off Pi
• Also, the car stereo expects a response from the CD changer every few seconds via I-Bus, otherwise it thinks that the CDC is not there
• Pi's boot time (20-30 sec) might be too slow to get music playing when the car stereo is up and running
• Thus we might need a small embedded controller that can be powered all the time or woken up quickly to listen for I-Bus messages and then switch the Pi on/off
  • Planning to use Arduino for this

  • Another option is a ?RuuviTracker (http://www.ruuvipenkki.fi/ruuvitracker/Etusivu) but its not available yet

• Alternatively, the controller could start when the car gets a signal to unlock the doors and then immediately switch Pi on. This would give us usually some seconds before the user expects to hear music from the speakers