Traditionally, for every electrical device in a car, the manufacturer ran a wire from a power source, via a fuse and then a switch, to the device and then to ground. When you turned the switch on and the device was energized. With the complexity of the modern car, the system soon became fraught with the possibility of failure. Advances in the computer industry have brought new technology to the automobile engineer and we are seeing more addressable network-based systems than ever before.
The electrical systems in the MINI are connected via a vehicle-specific wiring harness relative to the options that were factory installed. In addition there is a wiring harness within each door and a dashboard harness, again subject to the specified factory options. That describes the physical wiring within the car, but of a much more complex nature is the signal-specific connectivity that manages a host of systems and operations. These various signals travel over wires within the wiring harness and are digital in nature. They 'carry' information back and forth between sensors and devices and assist in much of the running of the car's systems, frequently unbeknown to the driver. These signal paths are know as 'buses' - a term from the computer industry that refers to data paths that connect the various parts of the computer together. Every bus carries signals or messages that consists of 'data,' 'control' and 'address' parts. When a command is sent out along a bus, the other devices ignore it as it is not addressed to them, however, when the data package arrives at the specified device, it does as it is commanded. The bus can also handle two way information so the remote device is capable of sending information back to the controller.
The MINI has a number of interconnecting bus systems: the K-bus, I-bus, CAN-bus, D-bus and the DS2-bus:
The K-Bus (from its German name Karosserie - meaning body) is the bus that permits messaging between various parts of the car and is what they call 'event driven'. Different things are given different priority on this bus, meaning some messages are given preferential treatment over others. The K-bus is a single white/red/yellow wire, and is a fairly slow bus - running at only a few kilobits per second and connects such items as the sun roof module, rains sensor (for rain sensing wipers where fitted), wiper interval control, headlight aiming controls (for Xenons), multi-function steering wheel, electronic drive-away protection (key and security systems), run flat monitor, multiple restraint system and the general (body control) module. The climate control also uses this bus along with other lighting and general body function items. These items can 'chat' back and forth with the general module using this bus, with obvious priority being given to items involving safety over say the entertainment system. The general module also communicates with the instrument cluster to pass information to the driver. This general module has the highest priority on this bus and its messages 'outrank' any others. All devices on this bus receive all the messages but as each message has an address header, they only respond to commands sent to them. This bus is designed as a 'tree structure' with each module having its own branch. This is so that a failed module on the bus, will not prevent a message getting to another module.
The I-bus is a subset or secondary K-bus and connects such devices as park distance controller, radio, CD player, digital signal processor and navigation system to the General Body Module. These buses comply with an international standard called ISO 9141 so that third party manufactures providing many parts to many OEMs can interchange parts.
The D-bus and the DS2-bus are serial diagnostic buses that allow both internal and external diagnostics to take place. The D-bus allows emission-related components to communicate with the on board diagnostic systems. These include the engine management module (ECU) the hydraulic power steering system and the ABS (anti-skid brakes), DSC and ASC (stability) systems. The DS2-bus connect non-emission related modules such as the steering angle sensor and the instrument cluster and subsequently allow data to be passed back and forth with the K-bus. Both of these diagnostic buses are connected to the OBDII diagnostic connector in the drivers foot well and allow the service department at your MINI dealership to look into the inner workings and see error and fault codes. Actually, the OBD is established as an ISO 9141 standard thus allowing repair shop diagnostic equipment to be useful across multiple manufacturer's vehicles. This bus also carries diagnostic information that it can share with other buses.
The CAN or Controller Area Network bus, is the fastest data speed bus in the vehicle and manages such things as engine management, ASC and DSC stability control systems and, where applicable, the automatic transmission. It is a serial data bus and employs twisted pair wires, yellow/black and yellow/brown. The high-speed nature of this demands specific wiring requirements, with termination requirements at both the ECU and the instrument cluster and no spur exceeding 1 meter. The use of twisted pair is very important to eliminate electromagnetic interference. It runs directly between the instrument cluster and the engine control module with three shorter network 'spurs' running off it to the steering sensor, the ABS/ASC/DSC module and if present, the automatic transmission control module. The CAN bus is a very versatile serial data bus system with multi-master capabilities, that is, all CAN nodes are able to transmit data and several CAN nodes can request the bus simultaneously. This is a fault-tolerant network and must work flawlessly in a very hostile electrical environment. The CAN vehicle bus used on the MINI was developed by BOSCH and is a remarkable piece of network engineering.
So there you have it... not one but five buses in the MINI. Of course, much of the MINI bus technology comes with the heritage of BMW and the E-46 3-series models 1999 - 2005. Another reason to appreciate just what BMW brings to the MINI.
(Posted by murmini on 02 November 2006)
murmini - MINI Cooper Blog : There is a BUS in my MINI
The electrical systems in the MINI are connected via a vehicle-specific wiring harness relative to the options that were factory installed. In addition there is a wiring harness within each door and a dashboard harness, again subject to the specified factory options. That describes the physical wiring within the car, but of a much more complex nature is the signal-specific connectivity that manages a host of systems and operations. These various signals travel over wires within the wiring harness and are digital in nature. They 'carry' information back and forth between sensors and devices and assist in much of the running of the car's systems, frequently unbeknown to the driver. These signal paths are know as 'buses' - a term from the computer industry that refers to data paths that connect the various parts of the computer together. Every bus carries signals or messages that consists of 'data,' 'control' and 'address' parts. When a command is sent out along a bus, the other devices ignore it as it is not addressed to them, however, when the data package arrives at the specified device, it does as it is commanded. The bus can also handle two way information so the remote device is capable of sending information back to the controller.
The MINI has a number of interconnecting bus systems: the K-bus, I-bus, CAN-bus, D-bus and the DS2-bus:
The K-Bus (from its German name Karosserie - meaning body) is the bus that permits messaging between various parts of the car and is what they call 'event driven'. Different things are given different priority on this bus, meaning some messages are given preferential treatment over others. The K-bus is a single white/red/yellow wire, and is a fairly slow bus - running at only a few kilobits per second and connects such items as the sun roof module, rains sensor (for rain sensing wipers where fitted), wiper interval control, headlight aiming controls (for Xenons), multi-function steering wheel, electronic drive-away protection (key and security systems), run flat monitor, multiple restraint system and the general (body control) module. The climate control also uses this bus along with other lighting and general body function items. These items can 'chat' back and forth with the general module using this bus, with obvious priority being given to items involving safety over say the entertainment system. The general module also communicates with the instrument cluster to pass information to the driver. This general module has the highest priority on this bus and its messages 'outrank' any others. All devices on this bus receive all the messages but as each message has an address header, they only respond to commands sent to them. This bus is designed as a 'tree structure' with each module having its own branch. This is so that a failed module on the bus, will not prevent a message getting to another module.
The I-bus is a subset or secondary K-bus and connects such devices as park distance controller, radio, CD player, digital signal processor and navigation system to the General Body Module. These buses comply with an international standard called ISO 9141 so that third party manufactures providing many parts to many OEMs can interchange parts.
The D-bus and the DS2-bus are serial diagnostic buses that allow both internal and external diagnostics to take place. The D-bus allows emission-related components to communicate with the on board diagnostic systems. These include the engine management module (ECU) the hydraulic power steering system and the ABS (anti-skid brakes), DSC and ASC (stability) systems. The DS2-bus connect non-emission related modules such as the steering angle sensor and the instrument cluster and subsequently allow data to be passed back and forth with the K-bus. Both of these diagnostic buses are connected to the OBDII diagnostic connector in the drivers foot well and allow the service department at your MINI dealership to look into the inner workings and see error and fault codes. Actually, the OBD is established as an ISO 9141 standard thus allowing repair shop diagnostic equipment to be useful across multiple manufacturer's vehicles. This bus also carries diagnostic information that it can share with other buses.
The CAN or Controller Area Network bus, is the fastest data speed bus in the vehicle and manages such things as engine management, ASC and DSC stability control systems and, where applicable, the automatic transmission. It is a serial data bus and employs twisted pair wires, yellow/black and yellow/brown. The high-speed nature of this demands specific wiring requirements, with termination requirements at both the ECU and the instrument cluster and no spur exceeding 1 meter. The use of twisted pair is very important to eliminate electromagnetic interference. It runs directly between the instrument cluster and the engine control module with three shorter network 'spurs' running off it to the steering sensor, the ABS/ASC/DSC module and if present, the automatic transmission control module. The CAN bus is a very versatile serial data bus system with multi-master capabilities, that is, all CAN nodes are able to transmit data and several CAN nodes can request the bus simultaneously. This is a fault-tolerant network and must work flawlessly in a very hostile electrical environment. The CAN vehicle bus used on the MINI was developed by BOSCH and is a remarkable piece of network engineering.
So there you have it... not one but five buses in the MINI. Of course, much of the MINI bus technology comes with the heritage of BMW and the E-46 3-series models 1999 - 2005. Another reason to appreciate just what BMW brings to the MINI.
(Posted by murmini on 02 November 2006)
murmini - MINI Cooper Blog : There is a BUS in my MINI