REXDESK: filter CAN IDs, J1939 PGNs and UDS requests

Record only the CAN messages that matter, by identifier or by J1939 address and PGN. You can also make the logger request diagnostic data from an ECU with UDS.

How filters work

A filter is a pass list. The logger records only the frames that match it and ignores the rest. Use a filter tool on a bus in place of Log All. Smaller logs are quicker to download and to search.

You can still drop Errors on the same bus to record its error frames. For background on filtering, read Understanding message filters in CAN.

CAN ID filters

1. Create a project. Select New Project on the toolbar.
2. Drop Filter on the bus. Drag Filter from the CAN group onto the bus you want to log.
3. Set the bus. Select the Bus icon and set the bus type and bit rate. See REXDESK: record CAN, CAN FD and LIN.
4. Enter a range. Select the Filter icon on the bus. In the CAN Filter panel, enter the range of identifiers to log in From CAN ID and To CAN ID.

   

5. Or pick from a DBC. Select the browse button (...) to choose identifiers from a DBC file in the library.
6. Add the range. Select Add. The range appears in the list. Use the buttons beside the list to add another filter, edit the selected one or remove it.
7. Set the log files and run. Set Storage and connect the logger over USB. Select Run, then save and name the project. Logging starts at once.

Watch: Set up CAN message filtering in a REXGEN series logger using a DBC file (1:11)

J1939 filters

The J1939 tool filters J1939 frames by source address, destination address and PGN. Use them together or one at a time.

1. Drop J1939 on the bus. In a new project, drag J1939 from the CAN group onto the bus. Set the bus as above.
2. Enter the values. Select the J1939 icon. In J1939 Filter Type, tick Source Address, Destination Address or PGN. Enter a value for each one you tick.

   

3. Or pick a PGN from a DBC. Select the browse button (...) beside PGN to choose one from a J1939 DBC.
4. Add the filter. Select Add. You can add, edit or remove filters in the list.
5. Set the log files and run. Set Storage and connect the logger. Select Run, then name the project.

Watch: Set up REXGEN series to log data using a J1939 filter (1:32)

UDS requests

The UDS tool makes the logger send diagnostic requests to an ECU over CAN and record the answers. You can then log values that are never broadcast. Drop UDS on a bus to open its Event messages window.

Use Add and Remove on the toolbar to add or delete a message. Use Move Up and Move Down to reorder the list. Each row is one request:

TX

The identifier the logger, acting as the tester, sends the request on.

RX

The identifier the ECU answers on.

Delay

The interval between messages.

Time Out

How long the logger waits for an answer before it treats the request as timed out.

Attempt

How many times the logger repeats the request.

Type

CAN Standard, CAN Extended, CAN FD Standard or CAN FD Extended.

BRS

Bit rate switch. Sends the data phase of a CAN FD frame at the higher bit rate.

DLC

The number of data bytes, from 0 to 8. CAN FD also allows 12, 16, 20, 24, 32, 48 or 64.

Data

The request bytes.

Put setup requests under SINGLE, such as the request that switches the ECU into its extended diagnostic session. Many data identifiers need that session. Put the requests you want logged over time under REPEATABLE.

New to UDS? Read Understanding UDS. To log OBD-II Mode 1 parameters, see REXGEN: log OBD2 Mode 1 PIDs.

Next: REXDESK: log analogue and digital inputs.