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WHAT IS CAN? Controller area network ( CAN/CAN-bus ) is a vehicle bus standard. Designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer. It is a message based protocol, designed for automotive applications . Development of the CAN-bus PROTOCOL -1983 at Robert Bosch ltd. Officially released in 1986 at the Society of Automotive Engineers. The first CAN controller chips, produced by Intel and Philips, came on the market in 1987.Bosch published the CAN 2.0 specification in 1991. The first production application was in 1992 . Manufacturers of CAN-compatible processors pay license fees to Bosch. CAN is one of five protocols used in the vehicle diagnostics standards.

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CAN allows various modules and systems to share data and interact in ways that where previously impossible via a common "data bus" circuit in the wiring system. A modern automobile may have as many as 70 electronic control units (ECU) for various subsystems. Typically the biggest processor is the engine control unit ;Power train Control Module . The CAN bus may be used in vehicles to connect engine control unit and transmission, or on a different bus to connect the door locks & windows, climate control, seat control, airbags, antilock braking, cruise control, EPS, audio systems & other modules to be interconnected. A subsystem may need to control actuators or receive feedback from sensors. The CAN standard was devised to fill this need.


TECHNOLOGY CAN is a serial bus standard for connecting electronic control units. Each node is able to send and receive messages, but not simultaneously. A message consists of an id, which represents the priority of the message, up to eight data bytes and is transmitted serially onto the bus. The devices that are connected by a CAN network are : Sensors -A sensor is a device that measures a physical quantity & converts it into a signal which can be read by an observer or by an instrument. Actuators -An actuator is a mechanical device for moving or controlling a mechanism or system and other control devices.

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Sensors and Actuators are not connected directly to the bus, but through a host processor and a CAN controller. If the bus is free, any node may begin to transmit. If two or more nodes begin sending messages at the same time, the message with the more dominant id (which has more dominant bits, i.e.zeroes) will overwrite other nodes less dominant ids, so that eventually only the dominant message remains & is received by all nodes. This mechanism is referred to as priority based bus arbitration. Bit rates up to 1 Mbit/s are possible at network lengths below 40 m. Each node requires a: Host processor CAN controller Transceiver

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Host processor The host processor decides what received messages mean and which messages it wants to transmit itself. Sensors,actuators,control devices can be connected to the host processor. CAN controller Receiving : CAN controller stores received bits from the bus until an entire message is available,which can be fetched by the host processor. Sending : the host processor stores its transmit messages to a CAN controller, which transmits the bits serially onto the bus. Transceiver (integrated into the CAN controller) Receiving : it adapts signal levels from the bus to levels that the CAN controller expects & has protective circuitry protecting CAN controller. Sending : it converts the transmit-bit signal received from the CAN controller into a signal that is sent onto the bus.


Layers Application Layer -It provides objects and services for communication, identifier distribution, network and layer management. -Furthermore it offers mechanisms for the initialization and monitoring of nodes. Object Layer Message Filtering Message and Status Handling

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Transfer Layer represents the kernel of the CAN protocol. It presents messages received to the object layer and accepts messages to be transmitted from the object layer. It performs: -Fault Confinement & Error Detection -Message Validation & Acknowledgement -Transfer Rate and Timing -Information Routing Physical LayerCAN bus in its original form was a link layer protocol specification that made reference to the physical layer only in abstract terms (i.e. as a medium that supported multiple access at the individual bit level by providing dominant and recessive states).

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Security CAN is a low-level protocol, and does not support any security features intrinsically. Applications are expected to deploy their own security mechanisms; e.g., to authenticate each other. Failure to do so may result in various sorts of attacks, if the opponent manages to insert messages on the bus. Password mechanisms exist for data transfer that can modify the control unit software, like software download or ignition key codes, but usually not for standard communication.


CAN FAULTS Module connectors become loose Wires get shorted or grounded Battery power is lost or battery is dead High vehicle noise generates disruption to signal and breaks network Loss of communication codes



What is MATLAB?:

What is MATLAB? MATLAB ® is a high-level technical computing language for algorithm development, data visualization, analysis and numeric computation. Using the MATLAB product, you can solve technical computing problems faster than with traditional programming languages, such as C, C++, and Fortran. You can use MATLAB in a wide range of applications: -signal and image processing -communications, -test and measurement -financial modeling and analysis.

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Key Features Technical computing Development environment for managing code, files, and data Tools for iterative exploration, design, problem solving Mathematical functions for linear algebra, statistics, Fourier analysis, filtering, optimization. 2-D and 3-D graphics functions for visualizing data Tools for building custom graphical user interfaces Functions for integrating MATLAB based algorithms with external applications and languages, such as C, C++, Java.

Vehicle Network Toolbox :

Vehicle Network Toolbox The Vehicle Network Toolbox provides the ability to communicate with in-vehicle networks using Controller Area Network (CAN) protocol an monitor CAN traffic. VNT Provides the following features: CAN Connectivity The V N T provides CAN connectivity using defined CAN devices & CAN network by which different control systems in a vehicle function. In a common design when you press a button to lock the doors in your car, a control unit in the door reads that input and transmits lock commands to control units in the other doors. These commands exist as data in CAN messages, which the control units in the other doors receive and act.

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Vehicle Network Toolbox Functions Using a set of well-defined functions, you can transfer messages between the MATLAB workspace and a CAN bus using a CAN device. You can run test applications that can log & record CAN messages for you to process & analyze. You can also replay recorded sequences of messages. CAN Tool Interface Using this simple graphical user interface, you can monitor message traffic on a selected device and channel & then analyze these messages.

Interaction between network tool box and components:

Interaction between network tool box and components

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Before using the familiar with these products: •MATLAB — To write scripts and functions, and to use functions with the Command-line interface . Simulink—To create simple models to connect to a CAN bus or to simulate those models . Vector CANdb — To understand CAN databases and message and signal definitions .

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