CAN Bus & CANAnalyser Troubleshooting

Display Issues

If the program has issues where the display of the tabs are cut off or columns appear truncated, a recommended resolution of 1920 x 1080 at 125% scale is suggested. Scale settings over 150% are not supported!

Check wiring

If the dongle is connected properly to the SLSS CANAnalyser and there is no Incoming data, it may be caused by a wiring issue or a USB cable issue.

• Verify proper pinout for interfacing to the DB9 connector in the section titled “Connector Pinouts”. Make sure the polarity is correct for CAN H and CAN L.
• Look for any loose, shorted or damaged wiring, especially in long buses.
• Verify that the ground is shared between all CAN nodes.
• Ensure that the USB cable is a USB 2.0 or USB 3.0 data capable cable.
• Ensure the bus is properly terminated with 120-ohm resistors at both ends of the bus.

If the dongle has no LEDs lit up at all then the dongle is either not receiving proper power or the dongle is defective.

• Ensure USB cable is tested as a good cable.
• If using the DB9 to power the dongle on Lab CAN Pro, Storage CAN or Lab CAN, verify >7VDC is applied to pin 9.
• Do not power the Lab CAN Pro via both the USB connector and DB9 pin 9 (B+) at the same time.

Noise issues

If the dongle is connected properly to the SLSS CANAnalyser and there are erroneous or unexpected or missing data showing, there may be a noise issue.

• If the bus is too long or not shielded properly, it may pick up noise.
• Implement twisted pair wiring for High and Low pins per channel to reduce noise.

Matching bus types

If the dongle is connected properly to the SLSS CANAnalyser and there is no Incoming data or only partial CAN 2.0 data, it may be caused by a mixture or mismatch of CAN 2.0 and CAN FD nodes.

• Ensure all nodes are using either CAN 2.0 or CAN FD-compliant nodes, as mixing CAN 2.0 and CAN FD nodes may cause unexpected results.
• IF CAN FD is required, ensure all nodes’ controllers are CAN FD-compatible. CAN 2.0 controllers may misinterpret CAN FD messages, leading to errors.
• CAN 2.0 nodes are not compatible with CAN FD higher data rates

A bus with CAN 2.0 only nodes is very forgiving on the hardware connection configuration settings, however a bus with CAN FD and especially with bit rate switch is extremely sensitive to precise configuration so please verify the settings carefully!

Check arbitration bitrate setup

• Ensure that all nodes on the bus are configured to use the same nominal arbitration bit rate.
• Typical rates: 500 kbit/s or 1 Mbit/s.

Check data bit rate setup (CAN FD only)

• Verify that the bit rate setting matches the target bus configuration
• Ensure that the data bit rate multiplier is properly configured (usually a multiple of the nominal bit rate).

Verify if manual settings are required or not (CAN FD only)

• When not using the manual settings, set the multiplier to provide the correct data bitrate. Eg. Arbitration bitrate of 500 kbit/s with a multiplier of x8 equals 4000 kbit/s data bitrate
• When not using the manual settings, note that the sample point percentage is a default of 75%. Use manual settings if another sample point is required.

Synchronize timing segments (CAN FD only when activating the manual settings)

• For both arbitration and data bitrates, adjust prescalers, PSEG1, PSEG2, SJW and TDC to optimize bus performance based on network size and wire length.
• Check sample point settings to avoid improper sampling of the signal.
• Setting these improperly may cause unexpected problems and may even cause the bus to crash or go into bus off mode

Specific other hardware configuration issues

Other causes of data not being seen in the Incoming CAN Data tab may be caused by one of these settings

• If bus interaction mode is set to off
• Incorrectly configuring the configurable termination resistor setting. A bus must be properly terminated with 120-ohm resistors at both ends of the bus so if interfacing to an existing terminated bus, set them to disabled, otherwise ensure they are enabled. CAN FD buses are more sensitive to this setting so be cognizant of this setting

If trying to send messages in the Send CAN Messages tab does not produce the actual messages being sent on to the bus, it may be disabled in the hardware configuration

• Ensure that the Send CAN messages are enabled.

If interfacing to a CAN FD bus that used bit rate switch messages, extra care is required to avoid bus crash issues and missed messages.

Mixed BRS modes on the same bus

• Ensure that all nodes are set to either use or not use BRS. Mixing nodes with BRS enabled and disabled can cause arbitration issues.
• Do not add send messages with the same ID having CAN FD bit rate switch and without bit rate switch

Bus Off Errors

• This occurs when a node repeatedly fails to transmit or receive messages. If this occurs, try to reconnect the dongle to see if the dongle settings were the cause. If this does not work then the bus off error is caused by another node on the bus.

Only Channel A in available and certain features are not available

• If the drop-down menu is greyed out or you cannot select Channel B, the license file does not match the hardware dongle connected to it!
• Similarly, if certain features are not available, the license file does not match the hardware dongle connected to it!

The micro-SD card button is greyed out or unavailable

The micro-SD card window is both hardware and license dependent.

• This button is only accessible once the software has connected to a Lab CAN Pro module. The other hardware variants do not have micro-SD logging hardware.
• If a Lab CAN Pro is connected and the button is still unavailable, the license file does not match the hardware dongle connected to it. See “Diagnosing Specific Issues”.

Incoming data and logging stop while the micro-SD card window is open

• This is expected behavior and is not a fault. While the micro-SD Card window is open, CAN logging and data viewing are not processed. Close the window to resume normal traffic display and recording.
• The same behavior applies to the GPIO Interface window.

Standalone logging does not start after disconnecting from the software

Work through these checks in order:

• Checking the “Start of log recording” enable box alone does not enable the offline logging on the hardware. The configuration must then be sent to the dongle using the send button on the Standalone Log Recording tab.
• After disconnecting, verify the Connect LED is solid purple. Solid purple indicates standalone logging mode. A slow blinking purple LED means the dongle is in standalone send mode instead, which is configured from the Standalone Send Mode feature tab.
• Confirm the configured start trigger can actually occur: First message received – traffic must be present on the selected trigger channel; Upon Receiving an ID – that exact CAN ID must appear on the selected channel; External I/O trigger – GPIO 1 or 2 must be correctly wired, including a common ground reference, and must physically change state.
• Confirm the trigger channel drop-down (Channel A, Channel B or either channel) matches the channel the traffic is actually on.
• Verify the dongle remains powered once it is disconnected from the PC, either via the USB connector or via DB9 pin 9 (+7 V to +28 VDC), and that the supply is not switched off part way through the session.

The standalone hardware configuration is independent from the Hardware Configuration window at the top of the main screen. A wrong arbitration bitrate, a wrong CAN FD setting, or a channel set to off in the standalone configuration will produce an empty log even though live monitoring worked correctly a moment earlier. Verify the standalone configuration separately.

It is critical to avoid powering the Lab CAN Pro via both the USB connector AND pin 9 (B+) at the same time.

Logging stops before the end of the test

• A maximum recording time may have been selected in the trigger options. If no maximum is selected, logging continues until it is stopped or memory is full.
• Check the free space remaining on the micro-SD card. Logging ends when the card is full.
• Verify the supply to the dongle is uninterrupted for the whole session. An ignition-switched supply on pin 9, or a USB port that powers down, will end the session early.

A log file is listed but cannot be opened, downloaded or played back

• The offline logs use a proprietary .TXT format. A .txt file that is manually placed on the micro-SD card will still be displayed in the list, however it cannot be used by the software and cannot be played back to the bus.
• Confirm the file was actually recorded by the dongle’s own offline logging function.

The log file list is empty or a new recording is not listed

• Press the refresh button on the file list. This is required after a micro-SD card has been replaced in the dongle hardware.
• Confirm the micro-SD card is fully seated in the socket.
• If the list is still empty after a test session, the logging session most likely never triggered. See “Standalone logging does not start after disconnecting from the software” above.

Downloading a log file from the card takes a very long time

• This is expected for large files. The software calculates the approximate download time and asks the user whether to proceed.
• It is faster to eject the micro-SD card and transfer the file directly with a card reader in Windows Explorer.

GPIO or A2B events are missing from the standalone log

• GPIO event logging must be enabled on the Advanced Logging Features tab, and an ID must be selected from the drop-down for the events to be logged against.
• Check the on-change / receive interval selection. If logging on change is selected and the input never changes state, no entries will appear.
• A2B logging requires the Flextech Bus Monitor connected via the qwiic interface, and it must be configured via the proper LUA script to accept the interface.

The dongle keeps entering standalone logging mode when it should not

• Use the erase button on the Standalone Log Recording tab. This erases the stored settings and configuration and disables standalone logging when the dongle is not connected to the SLSS CANAnalyser software.

Standalone logging and standalone sending are stored and erased separately. Erasing one does not erase the other. The standalone send list is erased from the Standalone Send Mode feature tab.

Standalone Bus Playback puts no traffic on the bus

• Verify a valid, natively recorded log file is loaded. Files manually placed on the card are listed but cannot be played back.
• Verify the playback channel selection (Channel A, Channel B or both channels) matches the bus being monitored.
• Verify the standalone hardware configuration for that channel is not set to Listen Only or off, and that message sending is enabled for the channel.
• Verify the bitrate and termination resistor settings match the target bus. See the “Dongle HW Configuration” tab.
• Check the loop setting. A single pass of a short log file can complete before it is observed on the analysis tool.

The GPIO button is greyed out or unavailable

• This button is only accessible once the software has connected to a Lab CAN Pro module. GPIO is applicable to Lab CAN Pro only.
• If a Lab CAN Pro is connected and the button is still unavailable, the license file does not match the hardware dongle connected to it.

Incoming data and logging stop while the GPIO window is open

• This is expected behavior. While the GPIO Interface window is open, CAN logging and data viewing are not processed. Close the window to resume.

A GPIO input never triggers

• Ground reference. The GPIO pins require a ground reference to be connected between the external device and the dongle. The ground reference can be acquired from pins 3 or 6 on either of the DB9 connectors. A missing common ground is the most common cause of an input that never changes state.
• Confirm the master enable check box at the top of the I/O Triggered Control Functions tab is selected. Deselecting it disables the entire GPIO functionality.
• Use the I/O Overview tab to observe the live input state. If the state does not change there when the external signal changes, the problem is electrical or wiring related and not a configuration issue.
• Confirm the signal is wired to an input pin. GPIO pins 1 and 2 are inputs, pins 3 and 4 are outputs.
• GPIO inputs are protected from -28VDC to 28VDC. Verify the applied signal is within range and that it genuinely transitions between states.
• At overtemperature the regulator on the GPIO inputs is automatically turned off by the integrated thermal protection circuit. If the inputs stop responding after prolonged operation, remove the load, allow the module to cool and retry.

A GPIO input trigger does not send the expected message list

• The selected list must be populated. For example, if “CAN message list” is selected as the list to send, there must already be a list of messages ready to be sent within the primary “Send CAN messages” tab.
• Confirm the correct GPIO input source and the correct list are selected in the two associated drop-downs.
• Confirm message sending is enabled for the channel in the Hardware Configuration window and that the channel is not set to Listen Only or off.

A GPIO output does not drive the connected load

• GPIO outputs provide approximately 14 mA steady state at CMOS logic levels (0 V / 5 V). This is not sufficient to directly drive relays, lamps, solenoids or other inductive or high current loads. Use an external driver, transistor stage or relay module with its own supply.
• Verify the pin itself is switching by using the I/O Overview tab. Toggle the output ON/OFF and measure the pin. If the pin toggles correctly but the load does not respond, it is a drive capability or wiring issue rather than a software issue.
• Confirm the load is connected to an output pin. GPIO pins 3 and 4 are the outputs.
• All GPIO pins have short circuit protection. A shorted output can appear dead until the short is removed.

GPIO states are lost, or unexpectedly retained, when the dongle is disconnected

• This is controlled by the reset check box on the I/O Triggered Control Functions tab. When selected, disconnecting the dongle from the SLSS CANAnalyser software resets all GPIO inputs and outputs to the default off setting. When it is not selected, the settings will persist as long as the dongle is powered.

GPIO triggered bus logging produces no log file

• The log file name must not be left blank. If it is left blank the log will not be saved.
• Confirm the red record button activates when the trigger input goes “high”. Logging ends and the record button stops being red once the trigger transitions to the “low” state.
• Confirm the log file format is selected from the drop-down. Use the folder button on the same tab to open the save location directly in a Windows Explorer window.
• Note that the log only runs for as long as the trigger is “high”. A momentary push-button will produce a very short log. Use a latching or level-held signal for a longer session.

The GPIO status message does not appear in Incoming CAN Data or in the logfile

• Select the check box to include the GPIO status message ID, and choose the ID to be used from the drop-down list.
• Choose whether the event is logged on every I/O value change, or at a fixed receive interval. With on-change selected and a static input, no rows will appear.
• GPIO status rows are shown with the [GPIO] data type. If a message filter is active and that ID is hidden, the rows will not be visible. Check the Message Filtering window.
• Select a status ID that is not already present on the monitored bus, so that GPIO status rows are not confused with real bus traffic.

A Bus Triggered I/O database signal trigger never fires

• A database file must be loaded before the trigger conditions are selected. If no database is loaded, or if a different database file is desired, load it first and then build the condition list.
• Confirm the channel selected for the trigger matches the channel the signal is actually received on.
• Confirm the enable check box on that row is selected. An unchecked row is ignored and is not searched for a valid trigger condition.
• Review the mathematical operation (Equal / Not Equal / Less Than / Greater Than) and the trigger value. The value must be expressed consistently with the scaling and value table of the selected database signal.
• If the database file was updated after the condition list was created, the message and signal names may no longer match. Reload the database and rebuild the affected rows.

A bus triggered output fires once and then stays HIGH

• This is expected when the reset check box on that row is not enabled. Without it, each trigger is a “one shot” and the output will remain active “HIGH” for the remainder of the active session. Enable the reset check box to have the GPIO reset back to “LOW” after each trigger and be ready to be triggered again.

A Bit or Byte value trigger never matches

• Confirm the selected byte position exists within the actual DLC of the message. The DLC can be any byte position between 1 and 64.
• Confirm the CAN ID has been typed in the notation currently selected in the global data format drop-downs (Hexadecimal, Decimal or Binary).
• For a bit trigger, confirm the bit pattern is correct for the selected bit position.
• Use the Graphical Analyser Viewer or the Reverse Engineering feature tab first to confirm which byte or bit is actually changing, then build the trigger against it.
• Move the horizontal scrollbar to the right to review the operation and value columns of the Condition List that are off-screen by default.

The Graphical Analyser shows no graph in the CANData Viewer

• The PLAY button must be pressed in the SLSS CANData Viewer or the graph will not display. This is the most common cause of an empty graph in the viewer.
• Confirm at least one byte is enabled in the byte selection area of the graph window.
• Confirm the selected ID is not being hidden by Filter 1 or Filter 2.

A file will not load into the CANData Viewer

• The native load formats are .scdf, .scdv and .rcdf.
• The supported imports are PEAK™ .TRC V2.0 and V2.1 log files, PEAK™ .XMT send message list files, .ASC files, CSV files previously exported from SLSS CANAnalyser, and the standalone SD logging .TXT format.
• A standalone SD .TXT file must have been recorded by the dongle’s own offline logging format. A manually created or hand-edited .txt file will not load.

An imported CSV has misaligned columns or split data

• The CSV delimiter used at import must match the delimiter the file was written with. Select the correct delimiter character under the Settings menu before importing.
• CAN data may contain ASCII characters that conflict with a comma, which is why the delimiter is configurable on export as well. Check which delimiter was used when the file was exported.

An imported .XMT or .ASC file cannot be used in the main software

• Imported data appears on the “Additional data” tab of the viewer and must be converted first. Import the file, press the Save button, then choose the desired native SLSS CANAnalyser format and enter the file name. The converted native file can then be loaded in the main software.

The playback button in the CANData Viewer does not put data on the bus

• The playback CAN button in the viewer is a future application for playing recorded data back onto the live bus and is not yet functional.
• To play a recorded log back to a live bus today, use Standalone Bus Playback in the micro-SD Card window on a Lab CAN Pro module.

No human readable signal names or Designations are shown

• Load the database file with the load database file button, then press the last button in the feature button row to go through the loaded data rows and enhance them with the loaded database file data.
• Confirm the loaded DBC or LDF actually matches the data being viewed, and that it is applied to the correct channel.
• Alternatively, data that was enhanced in the main software before saving or exporting already contains the Designation and the list of human readable signals.

Messages are missing from the CANData Viewer

• Check the channel selector. The view can be set to CH_A only, CH_B only, or both channels.
• Filter 1 and Filter 2 are two independent layers of filtering and both remain applied. Right click on the filter list and select “Select all” to restore all messages.
• The advanced filter button in the viewer operates identically to the filter button in the main software. Check its settings as well.

The data search finds nothing

• Check the case matching icon beside the search field.
• Confirm the search text matches the currently selected display format for the ID and byte data (HEX, DEC or BINARY).

The CANData Viewer is slow or unresponsive with large files

• Large logs take longer to load, filter and export. See the “System Resources” tab for memory and CPU guidance, and note that the larger the log buffer, the longer it takes to save the exported data.
• For very large standalone SD logs, transfer the file with a card reader instead of downloading it over the USB connection.

PEAK™ and the .TRC formats are trademarks of PEAK-System Technik GmbH.

These checks apply when a Lab CAN Pro is combined with a Flextech Pocket A2B Bus Monitor (A2B 1.0 or A2B 2.0) through a Qwiic cable, either connected to the SLSS CANAnalyser software or in standalone logging.

Requirements checklist

• The Flextech Bus Monitor must have “AKT Automation power by Lua” added to the purchase. If the “Output of the A2B Bus Monitor” window shows that Lua support is not available, contact Flextech AKT to unlock Lua access on the Bus Monitor.
• The Lua script must be copied to the microSD card that came with the Flextech Bus Monitor (not the card in the SeRoSys dongle). It is available on the Downloads page under Scripts and Automation.
• A Qwiic cable is required to connect the SeRoSys dongle to the Bus Monitor.
• To see the 0xA2Bxxx IDs properly in Incoming Data and the Logfile Recorder, set the ID display format to HEX. In DEC or Binary they are much harder to read.

Erratic behavior of the Bus Monitor or the dongle when connected by the Qwiic cable

• A standard Qwiic cable bought separately contains 4 wires and the red wire MUST be cut for this setup. Otherwise 3.3 V can backfeed between the two modules and cause erroneous behavior.
• Confirm the cable is fully connected at both ends (the Bus Monitor and the SeRoSys dongle).

Status LED blinks red for about 5 seconds, then the Bus Monitor restarts

• The Lua script’s startup check could not communicate with the SeRoSys hardware over the Qwiic (I2C) cable. Check that the cable is fully connected at both ends and that its red wire has been cut. Unplugging the Qwiic cable simulates this error, which is a quick way to confirm the setup before a test.
• If the script was started with Run selected script, the Bus Monitor does not retry: after fixing the cable, open the Hardware Configuration in SLSS CANAnalyser, reconnect to the Bus Monitor and run the Lua script again.
• If it was started with Set as autostart, the 5-second red blinking and restart repeat until the cable problem is resolved. The next automatic restart then starts normally with a solid green Status LED.
• In standalone mode, power the SeRoSys dongle FIRST, then the Bus Monitor. If the Bus Monitor is powered first, you may see this error once before the dongle is ready.

Status LED is blinking red (continuously)

• The Bus Monitor detected an error in one of its major operations. Stop logging and check the Bus Monitor SD card and connections. See the Flextech documentation for details.
• Solid green means everything is working and no errors were detected.

The Bus Monitor misbehaves or you hear a high-pitched sound

• The Bus Monitor is not getting adequate USB power. Use a shorter USB cable (a long cable causes voltage loss, and the voltage must stay at 5 V).
• Use a USB port or power supply that provides a stable 5 V with at least 150 mA.

Status LED is solid green but no WAV file is created

• Constant logging does not store WAV files; only triggered pre-buffered logging does.
• Check the trigger wiring. The button connects to the GPIO and ground pins on the Bus Monitor, not on the SeRoSys dongle.
• Verify the I/O LED flashes red for 1 second when the button is pressed. If not, the trigger did not reach the Bus Monitor and no recording is created for that press.
• Make sure the button is connected to the GPIO selected in the Lua script (GPIO0 by default). To use GPIO1, edit only the TRIGGER_GPIO line in the Lua script.

No finalization prompt, or no “SLSS_Triggered_Log” files on the SD card

• If no trigger occurred during the session, the temporary data in the _tlb sub-directory is discarded the next time the dongle connects to the software, and no log or WAV file is kept.
• If the SD card shows no SLSS_Triggered_Log files, finalization has not been done yet and the data is still in _tlb. Put the card back in the dongle, connect to SLSS CANAnalyser, open the SD card window and finalize. Always finalize before removing the SD card or copying files from it.
• Each button press creates a separate recording, and unfinalized recordings from earlier sessions accumulate. The SD card window may therefore report more files than expected. Finalize them all, or finalize at the end of each session to keep sessions separate.
• If you decline to finalize, nothing is lost. The software asks again every time you open the SD card window, and new recordings are added to the pending ones.
• Do not delete or modify the _tlb sub-directory by hand. This removes any data not yet finalized.

Linked WAV file problems

• Each triggered log is linked to a WAV file in the SLSS_wav_files directory on the Bus Monitor SD card. The last entry of the log (ID 0xA2B032) shows the WAV filename counter in its Designation column. Look for the WAV file ending in that number.
• If several CAN logs reference the same WAV number, the WAV files were deleted from the Bus Monitor SD card before the CAN logs were finalized, which restarted its counter at 1. Finalize the CAN logs first, then clear files from the SD cards.
• Deleting files on either card does not break the link. The dongle and the Bus Monitor keep independent file counters, and the Bus Monitor fills missing numbers first.

Best practices checklist

• Use short USB cables and a stable 5 V source with adequate current.
• Cut the red wire on the Qwiic cable and fully connect it at both ends.
• Start with both devices running and configured (solid green Status LED).
• For triggered logging, connect the button to the selected trigger input on the Bus Monitor and confirm the I/O LED flashes red for 1 second on each press.
• After testing, reconnect the dongle to SLSS CANAnalyser, open the SD card window and finalize all pending files before removing or clearing any SD card.
• Keep a backup copy of both SD cards’ files for important test sessions.