5. DBC files

Version 1.2Software: FuelTech Vision 3.0Firmware: 00.03.00.01Products: FT700, FT470, VisionFT2026-10-13

#What a DBC is

DBC (CAN database) is a text file that describes a CAN network: which messages exist, who transmits each one and where each signal is within them. The format became the de facto industry standard. Manufacturers of dashes, transmission modules, sensors and dataloggers usually provide the equipment's DBC, and it is what you use to configure communication without having to decipher it bit by bit.

#Anatomy of a message

Each message starts with a BO_ line and is followed by one SG_ line for each signal:

One message and one signal in a DBC file. The numbers are explained in the table below.

No.	Field	Meaning
1	ID	Message identifier, in decimal (1600 = 0x640). An extended ID appears with bit 31 set, that is, with 2147483648 (0x80000000) added.
2	Message name	For human reading only.
3	Size	Number of data bytes (DLC).
4	Transmitter	The module that sends the message.
5	Signal name	For human reading only.
6	Start bit	Position of the signal in the frame (convention explained in chapter 3, Signals).
7	Size	Number of bits of the signal.
8	Byte order	@1 = Intel, @0 = Motorola.
9	Sign	+ = unsigned, − = signed.
10	Factor and offset	physical value = raw × factor + offset.
11	Minimum and maximum	Range of the physical value. Informational.
12	Unit	Informational.
13	Receivers	The modules that use the signal.

#Other common lines

Besides BO_ and SG_, a DBC usually has comment lines (CM_), attributes (BA_DEF_ and BA_; for example GenMsgCycleTime, the transmit period of each message, in milliseconds) and value tables (VAL_, which give a name to each value of a signal, such as 0 = Off and 1 = On). CAN FD messages are marked by an attribute, normally VFrameFormat, which says whether the frame is classic or FD.