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Import MAT-Files into MATLAB

Step 5 of 5 in Log Signals on an SD Card

After logging is complete, you can open MAT-files in MATLAB®, and use them for further analysis. Since the data points are stored in MAT files, you can directly open the files in MATLAB without converting them into any other format.

Remove the SD Card from the VEX® EDR V5 Robot Brain, connect the card to the host computer and read the .mat files from the explorer.

The files are named as <modelname>_<runnumber>_<indexnumber>.mat. The name of your Simulink® model is modelname. runnumber is the number of times the model is run. runnumber starts with 1 and is incremented by one for every successive run. indexnumber is the MAT-file number in a run. indexnumber starts with 1 and is incremented by one for every new file that is created in the same run.

Suppose that the name of the model is sdcard. In the first run, Simulink creates sdcard_1_1.mat file and starts logging data in this file. After the logging in the first file is completed, Simulink creates sdcard_1_2.mat file and continues logging data in this file. Likewise, the logging continues in multiple MAT-files until the Stop time is elapsed. If the same model is run again, the new files are named as sdcard_2_1.mat, sdcard_2_2.mat, and so on.

Note

Data loss occurs when:

  • The total file size exceeds the available SD card storage capacity.

  • The signal logging rate is faster than the SD card writing speed.

Combine MAT-files and Analyze Variables

You need to combine all the MAT-files obtained from the SD card into a single MAT-file by using the VEXV5_MAT_stitcher command, and then analyze the variables for logged data.

  1. Run the following command at the MATLAB prompt:

    VEXV5_MAT_stitcher(dir('*.mat'))

    where dir represents the absolute path of the directory that contains the MAT-files.

    This command combines all the MAT-files starting with the same name in the current directory into a single file. The order of the stitching is based on the numeric characters found at the end of the file name. The name of the stitched file ends with __stitched.mat.

  2. Load the stitched MAT-file. For example, run the below command if the name of the stitched file is sdcard_1__stiched.mat.

    load('sdcard_1__stiched.mat')

  3. To view the logged values, double-click the corresponding variable that appears in the Workspace window.

Log Signals on an SD Card