Geekmatica - HOWTO: Car2PC Install in 2000 E46 BMW 323i

I recently found out about the Car2PC line of USB to head unit (HU) adapters from indashpc.org. They allow you to interface your Car PC or other USB-compatible device to your head unit. The Car2PC emulates a CD changer. It supplies an aux in for your analog audio input, and a USB interface to allow you to read the HU btns from your computer. While it's kind of pricey, it's not much more expensive than other CD changer emulators, and gives you the USB interface as well. I decided to use this device to interface my Omnifi DMP1 MP3 player to my head unit and steering wheel buttons. The idea is to be able switch tracks with the steering wheel buttons of my Bimmer, and maybe add some shortcuts to playlists, etc via the HU's buttons. Since Openfi,a replacement firmware for the DMP1 is open source, it was possible to add the functionality to the DMP1.

My E46 2000 BMW 323i has the stock BMW Business cassette player head unit installed, which uses IBUS. Therefore, I obtained the Car2PC-USB adapter. There is also a model available for MBUS-compatible HU's, and Toyota/Lexus/Honda/Acura support is in beta testing. Here is what the unit looks like:

The 4 thin wires go to the head unit for power/ground, and IBUS connection. The black 10-pin connector is for CD changer emulation. Audio input is via a 1/8" stereo miniplug, and USB connector goes to your PC or other USB-compatible device. On the host side, the device looks like a USB->Serial adapter. There are two ways to program it: VCP (virtual comm port) mode, and FT (FTDI mode). I will be getting into more specifics in a future programming article.

At this point, I've already crimped on the connectors. The wire with the red wrap is twisted together with the unmarked wire before crimping.

The first step in removing the radio is to pry off the dash trim on the right:

Use a suitable flat plastic blade to pry it loose, then pull it straight out. I just wrapped my flat-bladed screwdriver with electrical tape. Here is what the dash looks like with it removed:

Note that there are 3 pink plastic receivers for the 3 pegs which protrude from the back of the trim (in my photo, the rightmost one is missing). Here is a backside view of the right side trim. Note the 3 large securing pegs:

Next, pry up the center trim from the right side:

This is the backside of the center trim:

With the center trim removed, there are 2 screws exposed, one on each side of the head unit. Mine were just Philips head, but I've heard that some cars have Allen or Torx screws.

Remove the screws, and pull out your head unit:

What's nice is these newer head units don't need to have the code entered when you reconnect the power, so that's one less nuisance to deal with. Here is what the back of the head unit looks like:

Pry up on the black harness connector to pop it off:

Here is the connector:

and the plug:

If you have a CD changer harness attached to the plug, you will need to remove it, because the audio input connector connects in its place. Pull out the blue clip to release it:

T-Taps are supplied with the Car2PC to connect into the harness:

Crimp them on to the following wires:

Function	Car2PC	Harness
GND	Black	Brown 15
+12V	Red	Red/Green stripe 9
IBUS	Blue	White/Red stripe 7

Be extra careful with the IBUS wire ... it's rather thin gauge, and I had to crimp T-Tap may not get a good tight connection unless you first tighten it up before crimping it on.

Make sure you have good solid connections by testing them with a continuity tester:

Snap the black harness connector back on to the back of the HU. Here is a closeup of the 10-pin audio connector:

It connects to where the CD changer's 10-pin harness used to be. Make sure the silver stripe part is on top, and insert it firmly:

At this point, you should turn on the HU. Press the CD button. If all the connections are good, you should see it switch to CD changer mode:

Notice that at this point, my cassette audio adapter is gone (goodbye, Coby cassette adapter... you served me well, but the constant grinding of your gears was too noisy at traffic lights). Connect an audio source to the mini phone plug jack and see if you are getting audio. You might want to run the supplied Winamp plugin with your PC, as well, to make sure everything is working as expected before you start putting everything back together. The Car2PC unit fits inside the dash, but the most difficult part of the install is getting it to fit in. I crammed it behind the bracket that receives the big center pin in the rear of the HU. Next, you need to get the USB and audio input wires into your glove box. Open your glove box. There are two tabs, one on each side, on the top:

Twist the tabs a quarter turn, and the fuse box door will swing down. I used a pair of nabbergrabbers purchased from a 99 Cent store to pull the wires through. Feed in the nabbergrabber from the top left of the fuse box compartment:

and then pull each wire through to the glove box:

There is enough space on the left side of the fuse box door to allow you to close it when the wires are coming through:

Push your radio back in, replace the two securing screws, and reattach the two dash trim pieces. Your install is done!

I will be posting the code for installing my Openfi to Car2PC interface in the next few days. It allows your HU and steering wheel buttons to control your Omnfifi DMP1!


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