Analyse REXGEN MF4 files in asammdf

Use asammdf, a free MDF4 viewer, to look at raw CAN and CAN FD frames from a REXGEN logger. In asammdf you can decode the frames with a DBC file and plot signals and GPS tracks. You can also export to CSV or MATLAB and merge several logs into one.

Before you start

A REXGEN logger records RXD files. asammdf reads MDF4 (.mf4), so export your logs to MDF4 first. Use one of these tools.

• REXDESK. See REXDESK: download and export your logs.
• REXDESK Convert, from a script. See REXDESK: convert, configure and reflash from the command line.
• Your own code. See REXLIBRARY: convert RXD logs and XML configurations in your own code.

asammdf is an open-source project licensed under the LGPL. Install it from the asammdf releases on GitHub, or with Python: pip install asammdf[gui]. The asammdf GUI documentation explains every panel.

View raw CAN frames

1. Open the file. Select File > Open and choose the .mf4 file.
2. Choose the frame fields. On the Channels tab, tick the parts of the CAN frame you want to see, such as CAN_DataFrame.ID, CAN_DataFrame.DLC and CAN_DataFrame.DataBytes.

   

3. Open a table. Select Create window at the bottom of the panel and choose Tabular. The frames appear one per row, with their timestamps.
4. Filter if you need to. Use Add new filter and Apply filters to narrow the rows, for example to one identifier.

   

Export raw frames to CSV or MATLAB

1. Open the file. Select File > Open and choose the .mf4 file.
2. Go to the Export tab. Select the Export tab on the left.
3. Choose the format and options. Select the type, such as csv or mat, and set its options, such as a single time base or time from 0 s.

   

4. Export. Select Export and choose where to save the file.

Decode signals with a DBC file

A DBC file turns raw frames into named physical values such as engine speed or battery voltage. For how DBC files work, see understanding CAN DBC files.

1. Open the file. Select File > Open and choose the .mf4 file.
2. Go to the CAN logging tab. Select CAN logging in the panel on the left.
3. Load the database. Select Load CAN database and choose your DBC file.

Save the decoded signals as CSV

1. Set the CSV options. Choose the time base, raster and how to handle empty channels.
2. Export. Select Export to CSV and choose where to save the file.

   

Save the decoded signals as MF4

1. Set the MDF options. Choose the compression and the MDF version, for example 4.11.
2. Extract. Select Extract CAN signals and choose where to save. The new file opens, ready for plotting.

   

Plot decoded signals and GPS tracks

1. Open the decoded file. Open the MDF4 file you saved with Extract CAN signals.
2. Choose the signals. Tick the signals you want on the Channels tab.
3. Create a window. Select Create window and choose Plot for graphs, Tabular for a table or Numeric for a numeric view. You can open several windows side by side.

   

4. Plot a GPS track. Choose the GPS window type and select OK. Use the search button to find your latitude and longitude channels, then select Apply to draw the track on the map.

A GPS track needs latitude and longitude in the log. REXGEN 2 IMU GNSS, REXGEN Air and REXGEN Pro record them.

Merge several log files

1. Switch mode. Select Mode > Batch processing.
2. Go to Concatenate. Select the Concatenate tab on the left.
3. Add the files. Select File > Open and choose every file to merge. You can select several at once. Drag the rows to change the order, from top to bottom. Press Del to remove a file.
4. Merge. Choose the settings, including an output format of 4.0 or higher, then select Concatenate. asammdf writes one MDF4 file.