IBUSInsideDRAFTREV5.pdf

I-BUS Inside

Inside the BMW Cars entertainement Serial Bus

Written by Franck Touanen.

HackIBus@Yahoo.fr

2002, December.

Version DRAFT. REV 5.

Introduction and warning ................................................................................ 4

Bus in automotive applications....................................................................... 5

I-Bus General Architecture ............................................................................. 7

I-Bus Messages.............................................................................................. 8

Typicals Device IDs ................................................................................. 8

I-Bus Packet Structure............................................................................. 9

Hardware to read/write I-BUS ...................................................................... 10

Basic Interface ....................................................................................... 10

Contention Detection Interface .............................................................. 11

Melexis Chip Interface ........................................................................... 11

I-BUS Analyser software .............................................................................. 12

The I-Bus Analyser Software. (V1.00) .................................................. 12

Steering Wheel Messages ........................................................................... 17

Messages to Radio (68H) ..................................................................... 17

Messages to Telephone (C8H).............................................................. 17

Instrument Control Messages (IKE) ............................................................. 18

Messages to OBC Text (E7H) ............................................................... 18

Board Monitor Buttons (Nav system) ........................................................... 20

Messages to Radio (68H) ..................................................................... 20

Messages to Navigation / Video (3BH).................................................. 21

Broadcast Messages (FFH)................................................................... 21

RADIO Messages ........................................................................................ 22

Messages to Navigation / Video (3BH).................................................. 22

Messages to Instrument Control Electronics – IKE (80H)..................... 25

Messages to CD Player (18H) ............................................................... 25

I-BUS INSIDE

CD PLAYER Messages ............................................................................... 27

CD Player behaviour ............................................................................. 27

Broadcast Messages (FFH)................................................................... 27

Messages to Radio (68H) ...................................................................... 27

Navigation / Vidéo module Messages.......................................................... 28

Messages to IKE (80H) ......................................................................... 28

I-BUS INSIDE

Introduction and warning

A part of this information is based on research done by Thomas L. Wood, who has connected a Linux

embedded PC in his E39 (without NAV) to play MP3 . After exchanges with Thomas, I built my own interface

to start I-Bus analysis with the objective to interface a MP3 pic based player fully integrated with the board

monitor.

Note that all this document is based on analysis done in a E39 (July 2000) with a MK II navigation system.

I can't ensure if informations and/or device behaviours are identical for others models.

DISCLAIMER :

I'm not related in any way with BMW AG or any of its subsidiaries. All trademarks are property of their

respective owners. Any copyrighted information in this document belonging to third parties is presented for

non-commercial purposes only and purely for sake of education, scholarly analysis or criticism under the Fair

Useage terms of copyright law.

This document is unofficial and informations it contains can cause some problems to your car if you don't know

what your are doing, and I suppose, could cancel the Guarantee. USE THIS AT YOUR OWN RISK. I disclaim

anything.

This document is free ; you can redistribute it and/or modify it under the terms of the GNU General Public

License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any

later version.

This document is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even

the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License along with this document; if not, write to

the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

If you find errors or missing things, you can mail me at HackIBus@yahoo.fr .

I-BUS INSIDE

Bus in automotive applications

A bus is basically a shared communication link.

It's a collection of wires through which data is transmitted from one part of a computer to another. You can think

of a bus as a highway on which data travels within a computer.

In your computer, you can find e.g. a PCI bus to establish communication between extension cards and the

CPU, the memory bus, the AGP bus for video, the Universal Serial Bus for high speed serial devices …

In your BMW, a bus is used to establish communication between security equipments, for engine control, or

for entertainement devices (the famous IBus).

In automotive application, 2 mains bus architecture are used (others are often derivated from) :

The CAN bus and the LIN bus.

CAN Bus (Controller Area Network)

The CAN Bus was developed by Robert Bosch, GmbH. It combines extensive error checking with a high data

throughput to create an extremely powerful platform for local communication. CAN has an event driven, priority

based protocol which means that any device may attempt to communicate on the bus, but priority is given to

the node with a greater priority “message identifier”.

Physically the CAN system is based around a single twisted pair of conductors, but can be realised on a

number of mediums, including single wire and fibre optic. This configuration is quite robust and allows for 1 wire

to be broken, shorted to ground or shorted to power (with reduced signal to noise).

Currently CAN is very popular in Germany (it’s country of origin) and in Europe, but has not penetrated many

other markets effectively. However, it is predicted that by the year 2002 US car manufacturers will be using

CAN in volume.

LIN Bus (Local Interconnect Network)

LIN is a relatively new bus. It was developed through the collaboration of several companies, namely; Audi,

BMW, Daimler-Chrysler, Motorola GmbH, Volcano Communications Technologies, Volvo and Volkswagen.

LIN is based on the ISO 9141 specification. The network layout of the system uses a single wire 12V bus, one

master and several slave nodes. The slave nodes have no knowledge of the other nodes on the network

except the master node, and the master node controls communication on the bus. LIN is optimal for

applications such as doors, steering wheels, seats, climate regulation, lighting, rain sensors, or alternators.

The LIN protocol was not designed to be a competitor to the controller area network (CAN) protocol or other

high level system. It aims at applications that don’t require the flexibility and data rate of CAN. Thus it is

possible for the two systems to be implemented in the one vehicle, and even for the LIN and CAN networks to

share data through a gateway. LIN is designed for use in applications that will provide enhanced features in the

automobile, but where the cost of using CAN implementations is prohibitive. See diagram below.

I-BUS INSIDE

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