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DBC_Specification.md

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Scope

This document doesn't claim to specifiy the complete Vector DBC standard

Format description

<...>: Required field [...]: Optional field | : Or (eg. <A|B>)

Supported Keywords

VERSION

Version identifier of the DBC file. Format: VERSION "<VersionIdentifier>"

NS_

Names used throughout the DBC file. Format::

NS_:
    BS_
    CM_
    ...

BS_

Bus configuration. Format:: BS_: <Speed> Speed in kBit/s

BU_

List of all CAN-Nodes, seperated by whitespaces.

BO_

Message definition. Format: BO_ <CAN-ID> <MessageName>: <MessageLength> <SendingNode> MessageLength in bytes.

SG_

Signal definition. Format: SG_ <SignalName> [M|m<MultiplexerIdentifier>] : <StartBit>|<Length>@<Endianness><Signed> (<Factor>,<Offset>) [<Min>|<Max>] "[Unit]" [ReceivingNodes] Length in bits. Signed: + = unsigned; - = signed Endianness: 1 = little-endian, Intel; 0 = big-endian, Motorola M: If M than this signals contains a multiplexer identifier. MultiplexerIdentifier: Signal definition is only used if the value of the multiplexer signal equals to this value.

CM_

Description field. Format: CM_ [<BU_|BO_|SG_> [CAN-ID] [SignalName]] "<DescriptionText>";

BA_DEF_

Attribute definition. Format: BA_DEF_ [BU_|BO_|SG_] "<AttributeName>" <DataType> [Config];

DataType Description Config format
INT integer <min> <max>
FLOAT floating point <min> <max>
STRING string
ENUM enumeration "<Value0>","<Value1>"...

BA_DEF_DEF_

Attribute default value Format: BA_DEF_DEF_ "<AttributeName>" ["]<DefaultValue>["];

BA_

Attribute Format: BA_ "<AttributeName>" [BU_|BO_|SG_] [Node|CAN-ID] [SignalName] <AttributeValue>;

VAL_

Value definitions for signals. Format: VAL_ <CAN-ID> <SignalsName> <ValTableName|ValTableDefinition>;

VAL_TABLE_

Value table definition for signals. Format: VAL_TABLE_ <ValueTableName> <ValueTableDefinition>; ValueTableDefinition: List of IntValue "StringValue" Pairs, seperated by whitespaces

BO_TX_BU_:

Transmitter for signals. Format: BO_TX_BU_ <CAN-ID> : [BU_ seperated by commas]

SIG_GROUP_:

Group signals assigned to one can-id. I guess it makes it easier to parse and assign the correct signals like this. Format: SIG_GROUP_ <CAN-ID> <IntValue> : [Signal];

Attributes

In this sections are standard attributes used by CANpy defined. The attributes can be overwritten within a DBC file.

Message Attributes

GenMsgSendType

Defines the send type of a message. Supported types:

  • cyclic
  • triggered
  • cyclicIfActive
  • cyclicAndTriggered
  • cyclicIfActiveAndTriggered
  • none Definition: BA_DEF BO_ "GenMsgSendType" ENUM "cyclic","triggered","cyclicIfActive","cyclicAndTriggered","cyclicIfActiveAndTriggered","none" Default: none Definition: BA_DEF_DEF "GenMsgSendType" "none"

GenMsgCycleTime

Defines the cycle time of a message in ms. Definition: BA_DEF BO_ "GenMsgCycleTime" INT 0 0 Default: 0 Definition: BA_DEF_DEF "GenMsgCycleTime" 0

GenMsgStartDelayTime

Defines the allowed delay after startup this message must occure the first time in ms. Definition: BA_DEF BO_ "GenMsgStartDelayTime" INT 0 0 Default: 0 (=GenMsgCycleTime) Definition: BA_DEF_DEF "GenMsgStartDelayTime" 0

GenMsgDelayTime

Defines the allowed delay for a message in ms. Definition: BA_DEF BO_ "GenMsgDelayTime" INT 0 0 Default: 0 Definition: BA_DEF_DEF "GenMsgDelayTime" 0

Signal Attributes

GenSigStartValue

Defines the value as long as no value is set/received for this signal. Definition: BA_DEF SG_ "GenSigStartValue" INT 0 0 Default: 0 Definition: BA_DEF_DEF "GenSigStartValue" 0

Sources

http://pisnoop.s3.amazonaws.com/snoop_help_dbc.htm http://www.racelogic.co.uk/_downloads/vbox/Application_Notes/CAN%20Format%20for%20VBOXII%20and%20PRO%20v4.pdf https://hackage.haskell.org/package/ecu-0.0.8/src/src/j1939_utf8.dbc http://www.ingenieurbuerobecker.de/downloads/CANtool_Manual.pdf