Description

This document explains how to use the Data Interchange Layer (DIL) system to instantiate a CAN driver in order to send and/or receive configured CAN messages.

• The CAN bus is a multi-master serial bus widely used in the automotive, automation and aeronautic domains.
• CAN devices are connected to each other via a two-wire linear bus terminated with a 120-ohm resistance (as defined in ISO 11898-2 standard).
• CAN frames can contain up to 64 bits of data (64 bytes for CAN FD) and are exchanged at a configurable bit rate from 50 Kbps to 1 Mbps (up to 8 Mbps for CAN FD).
• Each message must have a unique ID (11 bits in standard mode or 29 bits in extended mode).

This driver supports the below CAN device:

• Kvaser PCIe board.

Supported Features

The following is a list of the features supported by this driver:

• The driver is ISO 11898-1 and 11898-2 compliant.
• CAN FD Support (selectable by channel).
• The number of active channels is configurable (within the constraints of the hardware).
• The bit rate of each channel is configurable.
• The silent mode support.
• Message transmission and reception can be enabled/disabled in the console (cyclically transmitted messages are exempt).
• Transmission and reception buffers can be emptied in the console.
• Messages can be transmitted with a fixed or a dynamic ID.
• Messages can be received with a specific ID or in promiscuous mode.
• Endianness for each signal in a message can be chosen between Intel and Motorola formats.
• Messages have a 1-bit granularity.
• A gain and an offset can be applied to each signal within a message both in transmission and in reception.
• Statistics for each channel can be monitored.
• Flags for each transmitted message are configurable.
• Flags for each received message can be monitored.
• The timestamp of each received message can be monitored.
• Vector_XXX type of node can be imported to CAN configuration via DBC importer but will not be part of CAN communication.
• Simple signal multiplexing is supported for both transmission and reception of data.
• DBC files where a message is transmitted by multiple nodes are supported.

Configuration

The driver is entirely configurable via the RT-LAB interface. Users can select the type of CAN hardware, to add, delete and duplicate channels and messages to obtain the desired configuration.

General Configuration

The first parameters to be configured are found below:

Gain and Offset Specification

The gain and offset computation are described by the next two figures. 
In these ones, the driver operations are within the blue boxes, the OpInput and the OpOutput represent the standard data points coming from and going to the model and the CAN-BUS subsystem represents the real CAN network.

Reverse gain/offset computation option disabled

If reverse gain/offset computation option is disabled the operations are as follows.

Reverse gain/offset computation option enabled

If reverse gain/offset computation option is enabled the operations are as follows.

Channel configuration

By default, the driver is configured with a list of two channels.

Each channel has four parameters:

The following fields are available only when Custom is selected on the Arbitration bitrate field: (For more information on how to configure the value refer to the Kvaser bit timing calculator.)

The following fields are available only when Custom is selected on the Bitrate field: (For more information on how to configure the value refer to the Kvaser bit timing calculator.)

Bus Configuration

A bus is a container for a group of nodes.

Each bus has one parameter:

• Filename: This parameter is set if the bus is configured from the DBC importer wizard. It is blank otherwise.

Node Configuration

A node is a container for a group of messages.

Each node has one parameter:

• Channel ID: This parameter binds the messages in this node to a physical channel. Every message in the node will have the same channel ID.

Vector__XXX: This is a special node, and it acts as a dummy node in the CAN configuration. The messages which are part of this node will not be part of CAN data communication. According to the CAN DB standards, the messages and signals configured for the node Vector_XXX are used for neither transmission nor reception. The purpose of this node is to accommodate the messages and signals which have not been assigned to a node and whose configurations need to be validated in the CAN viewer.

Message Configuration

The following parameters are common to any message type:

• Mode: Select Transmission or Reception depending on the desired behavior.
• Channel ID: The ID of the physical channel this message will be transmitted or received on. This parameter is read-only and can only be set by modifying the channel ID of the node that contains the message.

If a message is to be transmitted, additional parameters must be set:

• Use dynamic ID:
  • If set to true, the CAN ID of the message is controlled during the simulation from the console. To achieve this, a connection is made on the new connectable ID created when this box is checked.
  • If set to false, the CAN ID is configured with the CAN ID parameter.
• CAN ID: ID of the message that represents a priority on the CAN bus. An ID equal to 0 represents the highest priority while the highest possible value represents the lowest priority.
• Specify DLC: The Data Length Code field can be computed based on defined fields of the message, or manually set to force a particular value.  Importing from a database file (DBC or ARXML) will automatically set this checkbox.
• Data length code: A drop-down providing the possible DLC choices is available when the Specify DLC checkbox is checked.  The list adapts its choices based on the type of CAN Channel: up to 8 bytes with classic CAN or up to 64 bytes with CAN FD.
• Enable cyclic transmission:
  • If set to true, the message is transmitted at the Transmit Rate parameter.
  • If set to false, a connection needs to be made on the Enable Message connection point for the message to be transmitted:
• Transmit rate (ms): The rate at which the message should be transmitted. Rate is given in milliseconds. A message with a transmit rate lower than the model timestep is transmitted every timestep.
• Enable dynamic transmit rate (ms): If set to true, the transmit rate for cyclic transmission is controlled during the simulation from the console. To achieve this, a connection has to be made on the new connectable "Transmit Rate" created when this box is checked. If set to false, the transmit rate is to be configured through the configuration parameter.
• Enable transmit rate resynchronization: If set to true, the dynamic transmit rate will be applied to the transmission immediately upon the rising edge of the resynchronization signal. To achieve this, a connection has to be made on the new connectable "Resynchronization Signal" when this box is checked. If set to false, the dynamic transmit rate will be applied to the transmission at the completion of the existing transmit cycle.

If a message is to be received, here are the additional parameters to be set:

• Use promiscuous mode: If set to true, the message is updated with the contents of every message received on the respective channel. If set to false, the CAN ID is to be configured with the CAN ID parameter.
• CAN ID: The message is updated with only the contents of messages that match this particular ID
• Buffer size: Number of frames to be received in one calculation step. Buffer connectables (flags, signals, ID, ...) are created for each frame.

Signals Configuration

Each message contains a list of one or more signals that can be configured as desired.

Each signal has ten parameters:

The table below lists the various signal types that can be inserted in each message:

Each frame can contain up to 64 bits of data, meaning that multiple combinations of signal types are possible.

CANdb Importer

Clicking on the CANdb importer button brings up the CANdb Importer wizard. This wizard simplifies the process of importing CAN configurations such as node, message and signal information from a CANdb file. The CANdb file must conform to the Vector standard.

• ARXML
• DBC

The configuration steps are different depending on the choice of file type (DBC or ARXML).

Follow the steps below to successfully import an ARXML file into the CAN configuration:

• Select the type of CANdb file: Click the radio button next to ARXML to import the ARXML type of file.
• Select Bus: A list of CANdb buses part of the selected ARXML file should be displayed after a successful import. At this point, you can enable the buses needed in the simulation. DBC files are created for each CANdb bus with respective configurations.

• Configure Nodes: At this point buses selected at the previous step are available in the Bus drop-down menu.
• Select a bus to display its nodes in the table.
• Enable the nodes necessary for the simulation and set their types.

A node can be either simulated or physical. Physical nodes are nodes that represent real devices on your CAN network. Simulated nodes can exchange messages with physical nodes. Communication between simulated nodes is only possible if they're physically connected in loopback.

The buttons with labels "Physical" and "Simulated" allow you to set all the nodes to one type. Note that the "Next" button will only be activated if at least one enabled message is of type Simulated. Only nodes selected as type "Simulated" will appear in the configuration.

• Select Messages: Clicking Next brings us to the Messages page.
• Select the bus from the drop-down menu to display the enabled nodes and in turn display messages for configuring.
• The messages are grouped by nodes and can be enabled or disabled as desired. Note that messages belonging to a node marked as physical are enabled by default and can not be modified. Also, simulated nodes with messages expected to be received from physical nodes are enabled by default but can be disabled if desired.

• Select Finish: Clicking Finish closes the wizard and returns you to the configuration section. In the configuration section, you should see all of the simulated nodes, enabled messages and their signals along with their respective buses.

Follow the steps below to import a DBC file into the CAN configuration:

• Select the type of CAN db file: Click the radio button next to DBC to import the DBC file type.

• Create new bus: Clicking the Create new button brings up a dialog allowing you to create a new bus by entering a name

• Select DBC file: Select the DBC file to import by clicking on the file explorer button. The DBC file name should appear in the text box as shown below.
• After this is done, the selected DBC file is linked to the newly created bus. A dialog window may appear if errors are found while parsing the DBC file.
• It is highly advisable to fix all errors found in the DBC file before starting the simulation.

• Configure Nodes: A list of nodes is displayed after a successful import.
• At this point, you can enable the nodes that you want to be part of the simulation and set their type.
• A node can be either simulated or physical. Physical nodes are nodes that represent real devices on your CAN network. Simulated nodes can send and receive messages with physical nodes. Simulated nodes can only communicate with each other if you have a physical loopback connection.
• The buttons labeled Physical and Simulated allow you to set all the nodes to one type. Note that the Next button is only activated if at least one enabled message is of type Simulated.
• Only nodes selected as "Simulated" appear in the configuration.

• Select Messages: Clicking Next brings us to the Messages page.
• The messages are grouped by nodes and can be enabled or disabled as desired. Note that messages belonging to a node marked as physical are enabled by default and can not be modified.
• Also, simulated nodes with messages expected to be received from physical nodes are enabled by default but can be disabled if desired.

• Select Finish: Clicking Finish closes the wizard and returns you to the configuration. In the configuration, you should see all of the simulated nodes, enabled messages and their signals.

All of the buses created can be accessed using the Select bus button. The importer is able to parse DBC files with multiple transmitting nodes for the same message.

Potential errors returned while importing a file and how to fix them

• Invalid node information: Ensure your node line follows the format BU_: abc def
• No node information found: Ensure your DBC file contains a line that starts with BU_.
• Invalid message at line: Ensure the message found at the indicated line matches the format: BO_ x abc: x def
• Invalid signal at line: Ensure the signal found at the indicated line matches one of the following formats:

SG_ abc : x|x@0+ (y,y) [y|y] def
SG_ abc : x|x@0- (y,y) [y|y] def
SG_ abc : x|x@1+ (y,y) [y|y] def
SG_ abc : x|x@1- (y,y) [y|y] def
SG_ abc M x|x@0+ (y,y) [y|y] def
SG_ abc M x|x@0- (y,y) [y|y] def
SG_ abc M x|x@1+ (y,y) [y|y] def
SG_ abc M x|x@1- (y,y) [y|y] def
SG_ abc mx x|x@0+ (y,y) [y|y] def
SG_ abc mx x|x@0- (y,y) [y|y] def
SG_ abc mx x|x@1+ (y,y) [y|y] def
SG_ abc mx x|x@1- (y,y) [y|y] def
SG_ abc : x|x@0+ (y,y) [y|y] ijk def
SG_ abc : x|x@0- (y,y) [y|y] ijk def
SG_ abc : x|x@1+ (y,y) [y|y] ijk def
SG_ abc : x|x@1- (y,y) [y|y] ijk def
SG_ abc M x|x@0+ (y,y) [y|y] ijk def
SG_ abc M x|x@0- (y,y) [y|y] ijk def
SG_ abc M x|x@1+ (y,y) [y|y] ijk def
SG_ abc M x|x@1- (y,y) [y|y] ijk def
SG_ abc mx x|x@0+ (y,y) [y|y] ijk def
SG_ abc mx x|x@0- (y,y) [y|y] ijk def
SG_ abc mx x|x@1+ (y,y) [y|y] ijk def
SG_ abc mx x|x@1- (y,y) [y|y] ijk def

• Legend: x is a positive integer and y can be any number. abc, def and ijk can be any character or set of characters.

Frame Viewer

The Frame Viewer is a visual representation of the signals in a frame. It is found when you select a message item. It is a square grid with 8 rows and 8 columns (given that a CAN frame is 64 bits or 64 Bytes if CAN FD is enabled). Each box represents a possible bit position in memory. The first box represents bit 0 (row 0, column 0) and the last box (row 7, column 7) represents bit 63 (or bit 512 if CAN FD is enabled).

Clicking on a signal item will result in a bit or set of bits to be highlighted in the Frame Viewer with an arrow drawn across.

The arrow indicates the start and end position of the memory range occupied by the signal. Changing the endianness of a signal could result in a change in the end bit. Hovering over the Frame Viewer will also show the name of the signal at that position.

The Frame Viewer also indicates when signals overlap (they share part or all of a memory range). In the figure below, byte 1 contains two overlapping signals: signal 2 and signal 9. Running a simulation with a configuration containing overlapping signals could lead to incorrect results.

Simple signal multiplexing

CAN DBC files allow for the multiplexing of signals in messages. Multiplexing of signals in CAN means to combine multiple signals with the same memory range in the data frame of a message. This method allows to reduce number of messages in the CAN configuration by combining two or more messages with the same meta data. Depending on the multiplex value, certain signals are selected for the data frame during the model execution.

The signal which contains the multiplex value is called multiplexer signal and the signal which depends on the multiplex value is called multiplexed signal.

Each multiplexed signal is identified by a multiplex value in the multiplexer mode.

There are two types of multiplexing:

• Simple signal multiplexing
• Extended signal multiplexing

Currently only simple signal multiplexing is supported. In this mode only one multiplexer signal can be defined in a message and each multiplexed signal can have only one multiplex value.

Overlap error detection is disabled for multiplexed messages because the multiplexed signals are normally overlapped. Therefore, the CAN Frame Viewer will not show any overlap errors.

Even though all signals are displayed, only certain signals are transmitted and received. In the case of a multiplexed message, the multiplex value on the multiplexer signal determines the signals of a data frame.

As seen in the screenshot below, there are some signals (BCS_HS_Load_01, BCS_HS_Load_02, BCS_HS_Load_3, BCS_HS_Load_04) which are identified by the multiplex value '0' in the multiplexer mode and some (BCS_HS_Vout_01, BCS_HS_Vout_02, BCS_HS_Vout_3, BCS_HS_Vout_04 ) which are identified by '1'. During the execution of the model, the value on the multiplexer signal (BCS_HS_Card1_Selection) determines the signals selected for the data frame.

If the multiplexer signal (BCS_HS_Card1_Selection) becomes '0', the data frame will contain the multiplexer signal, the signals (BCS_HS_Load_01, BCS_HS_Load_02, BCS_HS_Load_3, BCS_HS_Load_04) identified by '0' in the multiplexer mode and the signals identified by "Normal" in the multiplexer mode and vice versa if the multiplexer signal becomes '1'.

Connections

Once the driver has been configured as desired, the user must connect points in the model to points in the driver by using the designated RT-LAB interface.

This connection panel shows all the driver's and model's connectable points, once the model has been compiled. Users can also make connections to LabVIEW panels.

The driver's connectable points depend on the driver's configuration (number of channels, number of messages in each channel, if a message is to be transmitted or received, etc.).

The following lists the driver connectable points for channels, transmission messages, and reception messages.

Channel Connectable Points

Status

Flags

The thresholds are determined by the platform used.

• Software buffers refer to temporary buffers that hold data going to or from the hardware.
• Hardware buffers are the buffers present in the hardware.

Error Counters

Transmission Message Connectable Points

Status

Flags

Data

The number and names of signal connectable points of a message to be transmitted depending on the message configuration.

Reception Message Connectable Points

Status

The following connectable points are available for each buffered frame:

Flags

Data

The number and names of signal connectable points of a message to be received depending on the message configuration.

Limitations

The current version of the CAN driver has the following limitations:

• ISO 11898-1 and 11898-2 standards supported.
• Maximum number of channels: 4 per Kvaser card for all platforms.
• Supported bit rates: 50, 62, 83, 100, 125, 250, 500 and 1000 Kbps and up to 8 Mbps for CAN FD.
• Number of frames per message that can be received in one time step: 20 (Buffer size parameter value).
• The maximum value of UINT64 data is the maximum value of a double data, as RT-LAB UI interprets all data in double data type formats when displayed in UI.
• Enabling Bus Load feature: will slow down the CAN data communication.