REXDESK: record CAN, CAN FD and LIN

Set up a REXGEN to record every message on its CAN, CAN FD and LIN buses, then check the traffic live.

Before you start

• REXDESK and the REXGEN USB driver. See REXDESK: install the software and the REXGEN USB driver.
• The bit rate of each bus. REXDESK can also detect it. The Learn article CAN bus baud rate and its calculation explains the numbers.
• A short stub from the bus to the logger. The bus needs a 120 Ω terminator at each physical end and nowhere else. See CAN bus wiring: termination, cable length and grounding.

REXDESK shows slots for four CAN buses, a LIN bus and the input channels. Use only those your logger has. The specifications guide for your logger lists them. REXGEN 1, for example, has one CAN bus and no LIN.

Log every message

1. Create a project. Select New Project on the toolbar.
2. Drop Log All on each bus. Drag Log All from the CAN group of the Tools panel onto CAN0. Repeat for CAN1 to CAN3 as needed, up to four CAN buses.

   

3. Add error frames if you want them. Drop Errors on a bus as well to record its CAN error frames. See CAN error frames below.
4. Set each bus. Select the Bus icon on each bus and set its type and bit rate. See CAN and CAN FD settings below.
5. Set the log files. Select Storage under Device Configuration and choose the file length and size.
6. Connect the logger. Plug it in over USB. The status bar shows the logger status and its time.
7. Run the configuration. Select Run on the toolbar (or Config > Run > Run Config), then save and name the project. The logger names its log files after the project, loads the configuration and starts logging at once.

Watch: Set up REXGEN series to record CAN data (1:19)

CAN and CAN FD settings

Select the Bus icon on a CAN slot to open its Settings tab.

Type

CAN for classic CAN, CANFD for CAN FD.

Autodetect bus speed

The logger detects the bit rate itself.

CAN speed

The bit rate of a classic CAN bus, or of the arbitration phase of a CAN FD bus: 100 kbit/s to 1 Mbit/s.

CAN FD speed

The data-phase bit rate of a CAN FD bus: 1 Mbit/s to 8 Mbit/s.

Silent Mode

The logger listens on the bus without taking part in it.

CAN FD Non Iso

For ECUs that use the non-ISO CAN FD frame format. Clear it for ISO CAN FD.

Use Bit Timing

Unlocks Bit Timing, where you set the bus timing yourself for advanced configurations such as a non-standard bit rate.

For the difference between the two protocols, see the Learn article CAN vs CAN FD.

LIN settings

Drag Log All from the LIN group onto the LIN slot to record every LIN frame. To make the logger the LIN master, drop Schedule instead and load the schedule table from your LDF file. Select the LIN bus icon to open its settings.

Protocol Version

The LIN protocol version of the bus.

Baudrate (bit/s)

The bit rate of the LIN bus.

Time Base (ms)

The LIN time base. Frame slots are scheduled in this unit, usually 5 ms or 10 ms.

Time Jitter (ms)

The timing tolerance allowed for the master node, as given in the LDF file.

Master Mode

Makes the logger the LIN master. It becomes active when you load a schedule table.

Watch: Configure REXGEN to record LIN data (0:59)

New to LIN? Read LIN basics.

Storage settings

Select Storage under Device Configuration to open Master Partition.

Max Logging Time

The longest time one log file covers.

Max Log Size

The largest size one log file can reach.

REXDESK labels some controls SD, such as Format SD. On current loggers they act on the logger's internal storage.

View live data

1. Enable Live. Before you run the configuration, check that the Live button under Device Configuration is enabled. Live data works with Log All or with a Filter.
2. Run the configuration. Send it to the logger as above, with the logger still connected over USB.
3. Open the live window. Select Live on the toolbar.
4. Go online. Select Online to start the trace. Select it again to go offline.

The window shows the raw trace: time, bus, identifier, flags, data length and data. With a DBC linked to the bus it also shows decoded values. Clear empties the window, Export saves the trace as an .asc file and List switches to a list of parameters.

CAN error frames

With Errors on a bus, the logger records that bus's error frames in the ASAM format. In a trace, an error frame is a row with no identifier and a description in the data column.

Each error record can also carry two values the logger measures, which never appear on the bus:

FrameDuration

How long the frame took on the bus, in nanoseconds. It runs from the first bit of the start of frame to the end of the error delimiter.

BitPosition

The bit at which the error was found, counted from the start of frame (position 0), ignoring stuff bits.

Watch: Set up REXGEN series to log CAN errors (0:50)

For what causes each error, read CAN errors basics.

Next: REXDESK: download and export your logs.