Bus Health (Physical Checks)
Always check the target CAN Bus with a multimeter before connecting to ensure dangerous or damaging voltages are not present.
The tool's CAN Bus connector provides functional isolation from its USB ports to help protect devices connected to these ports. This isolation is not intended for safety and must not be relied upon as a safety feature.
Use this screen to perform a physical health check of a connected CAN Bus.
Perform a Scan
The Bus Health screen may be accessed via the Main Menu.
Performing certain actions with this tool may completely halt a CAN bus. You should not perform any actions on a CAN Bus until the system is deemed safe to do so.
When performing a test, the CAN Bus Debugger tool will pull CANH to ~5V and CANL to ground, forcing a dominant bus state for a short period of time. Before running the test, ensure that it is safe for the system under test to be completely stopped. A consequence of executing this test is that other devices on the bus may enter an error passive or bus off state.
To perform a test, connect CANH, CANL, and ground to the target system. Use the 'Start' button to begin the test. After a few seconds, the tool displays the test results, including measured termination resistance and a description of any faults. The CAN Bus Debugger tool can detect the following faults:
- CANL short to supply (potentially damaging condition - read below)
- CANL short to ground
- CANH short to supply
- CANH short to ground
- CANH or both CANH and CANL short to ground (sometimes cannot distinguish between these two)
- CANH short to supply and CANL short to ground (potentially damaging condition - read below)
- CANL and CANH short together
Some bus conditions may damage the CAN Bus Debugger, especially the programmable terminator. If a damaging condition is found, the tool may stop the test early and disable the use of the programmable terminator until the next device reset. If a damaging condition is found, disconnect the CAN Bus Debugger and locate the fault before continuing analysis.
Example Test Output
The examples below show the output from the CAN Bus Debugger tool when performing a bus health check under various bus conditions.
With two terminators present
With a single terminator present
While no terminator is present
While the CANH and CANL signals are shorted together
While CANL is shorted to ground
While CANH is shorted to ground
While CANL is shorted to supply
While CANH is shorted to supply