Ready to do a CANBUS acquisition but don’t have a .dbc file to decode the data? No problem!
In LMS Test.Lab 16A (and later) it is possible to record the raw CANBUS stream and decode with the .dbc file offline.
To record the raw CAN stream:
1. Open LMS Test.Lab Signature Testing. In the Channel Setup workbook, choose the “CAN Settings” view from the dropdown in the upper right.
2. Setup the raw acquisition as shown in Figure 2:
A: Select the Can Device used for the acquisition.
B: Enter a baud rate, for most vehicles this is 500000
C: Set the device to “Passive”
D: Click “Apply” to apply the settings.
E: Go back to the standard “Channel Setup” view.
3. Back in the standard “Channel Setup” view, you will notice a new pane: “Digital Bus Channels” in the lower left of the screen.
In this area, there is an option to “Save Raw Data”. Check on this option. The raw CAN stream will be acquired.
NOTE: Most SCADAS hardware is able to record raw CAN data for later decoding. However, Vector boxes will not support the recording of raw CAN streams. Vector boxes were primarily used with the Scadas III hardware before CAN was embedded in the XSI of the SCADAS Mobile / Recorder units, or the SYSCON, the CN4 card, or the SCADAS XS. Measuring OBDII channels is also not supported with Vector boxes.
Decode the raw CAN offline:
1. Replace the entire run into the Input Basket (replacing just the LDSF or RDDF is not sufficient). Right click on the run name and choose “Replace in Input Basket”.
NOTE: The LDSF contains the raw time data from the run. The RDDF contains the raw CANBUS stream. The RDDF and LDSF are separate files, though they are stored in the same directory.
NOTE: If there is no RDDF called “Digital Bus Data” it means the raw CANBUS was not recorded.
2. Time Data Selection workbook (see Figure 6):
A: Ensure the “Data Source” is set to “Input Basket”. Click “Replace” to import data.
B: Click the “Import digital bus channels” button (black arrow and two yellow lines).
C: Select the .dbc file corresponding to the CAN device.
D: It is recommended to change “Interpolation” from “Sample and Hold” to “Linear”.
E: Click “OK”.
F: New channels are created for all decoded CAN signals.
G: Save the decoded CANBUS channels into the project by pressing the “Save As…” button. The data will be stored in the project and can be viewed in the Navigator workbook.
3. The decoded CANBUS data is saved into the throughput file of a new folder in the Navigator workbook.
NOTE: Legislated OBDII signals do not get recorded in the raw can stream. They must be actively requested during acquisition. They are not broadcast on the CANBUS by default.
Note that this feature is supported on the built-in CANBUS interface on LMS SCADAS Mobile, LMS SCADAS Lab, and SCADAS XS.
Recording raw CANBUS is not available with the USB based Vector box used with SCADAS3.
That’s it! Enjoy the convenience of being able to save and decode the raw CAN stream!
Questions? Contact us!