Vehicle bus
Encyclopedia
A vehicle bus is a specialized internal communications network that interconnects components inside a vehicle
(e.g. automobile, bus, train, industrial or agricultural vehicle, ship, or aircraft). Special requirements for vehicle control such as assurance of message delivery, assured non-conflicting messages, assured time of delivery as well as low cost, EMF
noise resilience, redundant routing and other characteristics mandate the use of less common networking protocols. Protocols include Controller Area Network
(CAN), Local Interconnect Network
(LIN) and others. Conventional computer networking technologies (such as Ethernet
and TCP/IP) are rarely used.
All cars sold in the United States since 1996 are required to have a On-Board Diagnostics
connector, for access to the car's electronic controllers.
, in order to make the automobiles environmentally friendly.
With stringent limitations placed on the emission gases for the automobiles, it became impossible to attain this level of control without the help of on-board computing devices. On-board electronic devices have also contributed substantially to vehicle performance, occupant comfort, ease of manufacture and cost effectiveness.
At one time, a radio was likely the only electronic device in an automobile, but now almost every component of the vehicle has some electronic feature. As mentioned above some of the typical electronic modules on today's vehicles are the Engine Control Unit
(ECU), the Transmission Control Unit
(TCU), the Anti-lock Braking System
(ABS) and body control modules (BCM).
An electronic control module typically gets its input from sensors (speed, temperature, pressure, etc.) that it uses in its computation. Various actuators are used to enforce the actions determined by the module (turn the cooling fan on, change gear, etc.). The modules need to exchange data among themselves during the normal operation of the vehicle. For example, the engine needs to tell the transmission what the engine speed is, and the transmission needs to tell other modules when a gear shift occurs. This need to exchange data quickly and reliably led to the development of the vehicle network. The vehicle network is the medium of data exchange.
The automotive industry quickly realized the complexity of wiring each module to every other module. Such a wiring design would not only be complex, it would have to be altered depending on which modules were included in the specific vehicle. For example, a car without the anti-lock brake module would have to be wired differently than one that included anti-lock brakes.
The industry's answer to this problem was to create a central network in the vehicle. Modules could be 'plugged' into the network and would be able to communicate with any other module that was installed on the network. This design was easier to manufacture, easier to maintain and provided the flexibility to add and remove options without affecting the entire vehicle's wiring architecture. Each module, a node on the vehicle network, controls specific components related to its function and communicates with the other modules as necessary, using a standard protocol
, over the vehicle network.
Networks were not new, but their application to the vehicle was. The networks for the vehicles called for:
Although the vehicle network did not place too much emphasis on the data throughput
, the demand for more on-board computing is continuing to drive changes to these networks to provide higher-speed communication between modules.
Additionally, many major car manufacturers use their own proprietary
vehicle bus standards, or overlay proprietary messages over open protocols such as CAN.
data communication link from one electronic module to another was introduced in the 1980 model year Cadillac
s. The link was one wire point to point, linking the engine control module to the fuel data panel. In model year 1981 all GM passenger cars for the US market used a similar data link to a test connector for assembly line diagnostics. The value of this data in diagnosing emission systems after customer delivery was quickly identified. Scanner tools were made to view and interpret the data stream. The data line was the same line that turned on the "Check Engine" lamp in the instrument panel. Data was sent at 80 bits per sec. 9 bits per frame, 21 bytes (frames), 2.4 sec./transmission.
In 1981 model year Cadillacs, two 80 bit point to point links were present, with the second link going from the engine control module to the climate control module.
In the 1982 model year, fuel injection
engine control modules had the data port moved to a dedicated full time connection (Corvette
and 2.5 L engines).
In the 1983 model year, the data rate on the fuel injection engine control modules was doubled to 160 bit/s.
In the 1984 model year, Corvette Instrument panel used data from the fuel injection engine control module's data link.
In the 1985 model year, Cadillac FWD "C" vehicle had an electronic system that had point to point data links between 5 electronic modules and a dedicated assembly line diagnostic connector.
On the 1988 and 1989 model year Buick Reatta
and 1986-1989 model year Buick Riviera
touchscreen CRT equipped vehicles, an 8,192 bit/s data bus was implemented between the body computer module and the assembly line connector, climate control module, and CRT controller. This was GM's first multi-drop data bus. All GM vehicles adopted this bus as new engine control modules were developed. This bus remained the standard GM vehicle bus until 1996 when the J1850 VPW bus replaced it.
Vehicle
A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....
(e.g. automobile, bus, train, industrial or agricultural vehicle, ship, or aircraft). Special requirements for vehicle control such as assurance of message delivery, assured non-conflicting messages, assured time of delivery as well as low cost, EMF
Electromagnetic field
An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...
noise resilience, redundant routing and other characteristics mandate the use of less common networking protocols. Protocols include Controller Area Network
Controller Area Network
Controller–area network is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer....
(CAN), Local Interconnect Network
Local Interconnect Network
The LIN-Bus is a vehicle bus standard or computer networking bus-system used within current automotive network architectures....
(LIN) and others. Conventional computer networking technologies (such as Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
and TCP/IP) are rarely used.
All cars sold in the United States since 1996 are required to have a On-Board Diagnostics
On-board diagnostics
On-Board Diagnostics, or OBD, in an automotive context, is a generic term referring to a vehicle's self-diagnostic and reporting capability. OBD systems give the vehicle owner or a repair technician access to state of health information for various vehicle sub-systems...
connector, for access to the car's electronic controllers.
Background
The main driving forces for the development of vehicle network technology have been the advances made in the electronics industry in general and government regulations imposed, especially in the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, in order to make the automobiles environmentally friendly.
With stringent limitations placed on the emission gases for the automobiles, it became impossible to attain this level of control without the help of on-board computing devices. On-board electronic devices have also contributed substantially to vehicle performance, occupant comfort, ease of manufacture and cost effectiveness.
At one time, a radio was likely the only electronic device in an automobile, but now almost every component of the vehicle has some electronic feature. As mentioned above some of the typical electronic modules on today's vehicles are the Engine Control Unit
Engine Control Unit
An engine control unit is a type of electronic control unit that determines the amount of fuel, ignition timing and other parameters an internal combustion engine needs to keep running...
(ECU), the Transmission Control Unit
Transmission Control Unit
A transmission control unit or TCU is a device that controls modern electronic automatic transmissions. A TCU generally uses sensors from the vehicle as well as data provided by the Engine Control Unit to calculate how and when to change gears in the vehicle for optimum performance, fuel economy...
(TCU), the Anti-lock Braking System
Anti-lock braking system
An anti-lock braking system is a safety system that allows the wheels on a motor vehicle to continue interacting tractively with the road surface as directed by driver steering inputs while braking, preventing the wheels from locking up and therefore avoiding skidding.An ABS generally offers...
(ABS) and body control modules (BCM).
An electronic control module typically gets its input from sensors (speed, temperature, pressure, etc.) that it uses in its computation. Various actuators are used to enforce the actions determined by the module (turn the cooling fan on, change gear, etc.). The modules need to exchange data among themselves during the normal operation of the vehicle. For example, the engine needs to tell the transmission what the engine speed is, and the transmission needs to tell other modules when a gear shift occurs. This need to exchange data quickly and reliably led to the development of the vehicle network. The vehicle network is the medium of data exchange.
The automotive industry quickly realized the complexity of wiring each module to every other module. Such a wiring design would not only be complex, it would have to be altered depending on which modules were included in the specific vehicle. For example, a car without the anti-lock brake module would have to be wired differently than one that included anti-lock brakes.
The industry's answer to this problem was to create a central network in the vehicle. Modules could be 'plugged' into the network and would be able to communicate with any other module that was installed on the network. This design was easier to manufacture, easier to maintain and provided the flexibility to add and remove options without affecting the entire vehicle's wiring architecture. Each module, a node on the vehicle network, controls specific components related to its function and communicates with the other modules as necessary, using a standard protocol
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
, over the vehicle network.
Networks were not new, but their application to the vehicle was. The networks for the vehicles called for:
- Low cost
- Immunity from external noise
- Ability to operate in harsh environments
- Overall robustness and reliability
Although the vehicle network did not place too much emphasis on the data throughput
Throughput
In communication networks, such as Ethernet or packet radio, throughput or network throughput is the average rate of successful message delivery over a communication channel. This data may be delivered over a physical or logical link, or pass through a certain network node...
, the demand for more on-board computing is continuing to drive changes to these networks to provide higher-speed communication between modules.
Protocols, physical media and connectors
There are several network types and protocols used in vehicles by various manufactures. Many companies are encouraging a standard communication protocol, but one has not been settled on.Protocols
Common vehicle buses protocols include:- CANController Area NetworkController–area network is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer....
- (Controller Area Network) an inexpensive low-speed serial bus for interconnecting automotive components - VANVehicle Area NetworkThe Vehicle Area Network is a vehicle bus developed by PSA Peugeot Citroën and Renault. It is a serial protocol capable of speeds up to 125 kbit/s and is standardised in ISO 11519-3....
- (Vehicle Area Network) - FlexRayFlexRayFlexRay is an automotive network communications protocol developed by the . It is designed to be faster and more reliable than CAN and TTP, but is also more expensive...
- a general purpose high-speed protocol with safety-critical features - LINLocal Interconnect NetworkThe LIN-Bus is a vehicle bus standard or computer networking bus-system used within current automotive network architectures....
- (Local Interconnect Network) a very low cost in-vehicle sub-network - J1939J1939Society of Automotive Engineers SAE J1939 is the vehicle bus standard used for communication and diagnostics among vehicle components, originally by the car and heavy duty truck industry in the United States....
and ISO 11783ISO 11783ISO 11783 is a communication protocol based on the SAE J1939 protocol for the agriculture industry.It is managed by the ISOBUS group in VDMA....
- an adaptation of CAN for agricultural and commercial vehicles - MOST - (Media Oriented Systems Transport) a high-speed multimedia interface
- Multifunction Vehicle Bus - part of the Train Communication NetworkTrain Communication NetworkThe Train Communication Network is a hierarchical combination of two fieldbus systems for digital operation of trains. It consists of the Multifunction Vehicle Bus inside each coach and the Wire Train Bus to connect the MVB parts with the train control system...
IEC 61375. - D2BDomestic Digital Bus (automotive)Domestic Digital Bus, D2B, is an isochronous ring-based fibreoptical communications technology, with a bandwidth of 12 Mb/s, specified by the Optical Chip Consortium for use in automotive applications. As of 2007, D2B is used by Mercedes-Benz in their vehicles.- External links :* * *...
- (Domestic Digital Bus) a high-speed multimedia interface - Keyword Protocol 2000Keyword Protocol 2000Keyword Protocol 2000, abbreviated KWP2000, is a communications protocol used for on-board vehicle diagnostics systems . This protocol covers the application layer in the OSI model of computer networking...
(KWP2000) - a protocol for automotive diagnostic devices (runs either on a serialSerial cableA serial cable is a cable that can be used to transfer information between two devices using serial communication. The form of connectors depends on the particular PHY used...
line or over CAN) - DC-BUS http://www.yamar.com/benefits.html - Automotive power-line communication multiplexed network
- IDB-1394
- SMARTwireX
- J1850
- ISO-9141-I/-II
- J1708J1708SAE J1708 is a standard used for serial communications between ECUs on a heavy duty vehicle and also between a computer and the vehicle. With respect to Open System Interconnection model , J1708 defines the physical layer...
and J1587J1587J1587 is an automotive diagnostic protocol standard developed by the Society of Automotive Engineers for heavy-duty and most medium-duty vehicles built after 1985. The J1587 protocol uses different diagnostic connectors. Up to 1995, individual OEMs used their own connectors. From 1996 to 2001, the... - SPI
- IIC
Physical transmission media
Some examples of physical transmission media use in vehicle networks:- Single wireLocal Interconnect NetworkThe LIN-Bus is a vehicle bus standard or computer networking bus-system used within current automotive network architectures....
- Twisted Pair
- Fibre optic
- Power-line communicationhttp://www.yamar.com
Connectors
- OBD-2 (16 pin)
Additionally, many major car manufacturers use their own proprietary
Proprietary protocol
In telecommunications, a proprietary protocol is a communications protocol owned by a single organization or individual.-Enforcement:Proprietors may enforce restrictions through patents and by keeping the protocol specification a trade secret...
vehicle bus standards, or overlay proprietary messages over open protocols such as CAN.
Protocols usage
stub: please leave as this will be further filled and corrected| Protocol/Version | Start/End Year | Manufacturer | Vehicle Types | Application summary |
|---|---|---|---|---|
| FlexRay | 2008? | BMW | cars | - |
| FlexRay | 2008? | Volkswagen | cars | - |
| FlexRay | 2008? | Daimler AG | cars | - |
| FlexRay | - | General Motors | cars | - |
| CAN | 1986 | many (ISO 11898-1) | many | - |
| MOST | ? | Ford, BMW, Daimler, and GM | cars | - |
| J1850 | - | GM | cars | - |
| J1850 | 2008? | Chrysler | cars | - |
| J1850 | - | Ford | cars | - |
| APC | - | Ford | cars | - |
| ISO-9141-I/-II | 2008? | Ford | cars | - |
| VAN | 2008? | PSA Peugeot Citroën | cars | - |
| VAN | 2008? | Renault | cars | - |
| J1939 | 2005–present | many | heavy trucks (Class5-8) | - |
| J1708/1587 | 1985–present | Volvo AB, most US truck manufacturers | heavy trucks (Class5-8) | - |
| 1970? | Lockheed-Martin | aircraft | - | |
| 1970? | Lockheed-Martin | aircraft | - | |
Early history of buses on GM vehicles
The earliest known GMGeneral Motors
General Motors Company , commonly known as GM, formerly incorporated as General Motors Corporation, is an American multinational automotive corporation headquartered in Detroit, Michigan and the world's second-largest automaker in 2010...
data communication link from one electronic module to another was introduced in the 1980 model year Cadillac
Cadillac
Cadillac is an American luxury vehicle marque owned by General Motors . Cadillac vehicles are sold in over 50 countries and territories, but mostly in North America. Cadillac is currently the second oldest American automobile manufacturer behind fellow GM marque Buick and is among the oldest...
s. The link was one wire point to point, linking the engine control module to the fuel data panel. In model year 1981 all GM passenger cars for the US market used a similar data link to a test connector for assembly line diagnostics. The value of this data in diagnosing emission systems after customer delivery was quickly identified. Scanner tools were made to view and interpret the data stream. The data line was the same line that turned on the "Check Engine" lamp in the instrument panel. Data was sent at 80 bits per sec. 9 bits per frame, 21 bytes (frames), 2.4 sec./transmission.
In 1981 model year Cadillacs, two 80 bit point to point links were present, with the second link going from the engine control module to the climate control module.
In the 1982 model year, fuel injection
Fuel injection
Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines, having almost completely replaced carburetors in the late 1980s....
engine control modules had the data port moved to a dedicated full time connection (Corvette
Corvette
A corvette is a small, maneuverable, lightly armed warship, originally smaller than a frigate and larger than a coastal patrol craft or fast attack craft , although many recent designs resemble frigates in size and role...
and 2.5 L engines).
In the 1983 model year, the data rate on the fuel injection engine control modules was doubled to 160 bit/s.
In the 1984 model year, Corvette Instrument panel used data from the fuel injection engine control module's data link.
In the 1985 model year, Cadillac FWD "C" vehicle had an electronic system that had point to point data links between 5 electronic modules and a dedicated assembly line diagnostic connector.
On the 1988 and 1989 model year Buick Reatta
Buick Reatta
The Buick Reatta was the first car Buick advertised as a two-seater since the 1940 Buick model 46. It was a hand-made luxurious sports coupe produced at the Lansing Craft Centre in Lansing, Michigan and sold by the Buick division of American automaker General Motors from early 1988 to 1991...
and 1986-1989 model year Buick Riviera
Buick Riviera
The Riviera by Buick is an automobile produced by Buick in the United States from the 1963 to 1999 model years, with 1,127,261 produced.A full-size coupé or personal luxury car, the early models of the Riviera in particular have been highly praised by automotive journalists and writers.A common...
touchscreen CRT equipped vehicles, an 8,192 bit/s data bus was implemented between the body computer module and the assembly line connector, climate control module, and CRT controller. This was GM's first multi-drop data bus. All GM vehicles adopted this bus as new engine control modules were developed. This bus remained the standard GM vehicle bus until 1996 when the J1850 VPW bus replaced it.
External links
- http://www.interfacebus.com/Design_Connector_Automotive.html