11. Import and export DBC
#Where it is
On the Frames tab of Customizable CAN, in the desktop software, there are two buttons: Import DBC and Export DBC. They do not appear in the mobile and tablet app.
#What the import does
For each message in the file, in the order they appear, the import fills one frame:
| Frame field | Value after import |
|---|---|
| Enabled | On. |
| Custom name | Message name in the DBC. |
| ID and Extended ID | ID from the DBC. A message with bit 31 set in the DBC becomes Extended ID. |
| Bytes | Message size in the DBC. |
| Direction | TX, always. |
| Port | Port A, always. |
| Timeout | The message cycle in the DBC (GenMsgCycleTime attribute), when it exists; without it, 0.01 s. It only has an effect on an RX frame. |
| Period | Not changed. A new frame stays at 0.01 s (100 Hz). |
Each signal in the DBC becomes a signal in the bank with the same name, Start bit, Length, Bits ordering, Value type, Scale and Offset, with Arithmetic channel on and VCU Channel set to None.
#After importing: checklist
- Read the warning message: it lists almost all the messages and signals that were ignored. Also compare the summary "Imported N frames and M signals" with the DBC: signals dropped at the 48-signal limit at the end of a message do not generate a warning, and the pseudo-message VECTOR__INDEPENDENT_SIG_MSG (which some programs add to the DBC), if it exists in the file, takes up one of the 16 frames.
- In each frame, set the Direction: RX for what the VCU will read, TX for what it will send.
- Set the Port of each frame.
- In TX frames, set the Period (the DBC cycle is not applied to the Period). In RX frames, check the Timeout: the imported value is the DBC cycle (or 0.01 s) and may be below the minimum of 0.5 s; use at least three times the sender's period and never less than 0.5 s.
- In each signal, choose the VCU Channel: the source in TX frames and the destination (preferably a Custom measurement) in RX frames.
- Disable the frames you will not use. Frames beyond the imported ones keep the old configuration and have no signals; if they are enabled, disable them. The import does not check for a repeated ID: two RX frames with the same ID on the same port do not work (only the first one receives).
- On the CAN ports screen, check that the port used is on, in the right mode and at the right rate.
- Write the map and check the values in real time before using it.
#What is read from the file
| DBC item | Handling |
|---|---|
| BO_ (messages) | Read. Up to 16; the following ones are ignored, with a warning. |
| SG_ (signals) | Read. Up to 48 in total; signals longer than 32 bits are ignored, with a warning. |
| @0 / @1, + / − | Become Motorola / Intel and Unsigned / Signed. |
| (factor,offset) | Become Scale and Offset. |
| GenMsgCycleTime | Becomes the frame's Timeout (used only in RX). |
| Minimum, maximum, unit, receivers | Read and discarded. |
| Multiplexed signals | Imported as ordinary signals, which can end up overlapping. Choose one variant and delete the others. |
| Floating-point signals (SIG_VALTYPE_) | Not recognized: they come in as integers. Do not use. |
| CAN FD messages (VFrameFormat) | The FD format is not detected; the size is imported as is. Turn on the port's FD mode if you need it. |
| VAL_, CM_, other attributes | Ignored. |
#Export DBC
Export DBC generates a file with every frame that has at least one signal checked, enabled or not. The ID (with bit 31 on Extended ID frames), the name, the size, the signals (position, order, type, scale, offset) and the frame's Timeout as the message cycle come out (on a TX frame, the exported cycle is not the Period). The VCU channel, the direction, the port, the Period, the fixed value, the BRS and Force classic CAN do not come out. The exported file is for configuring the other equipment or an analyzer; it is not a backup of Customizable CAN. For that, save the map.