MATLAB: How to extract data from diagnostic​s_msgs/Dia​gnosticArr​ay ROS message type in Simulink

Question

Dear Mathworks community, I need to extract data from diagnostics_msgs/DiagnosticArray ROS message type in my Simulink model. The message definition in ROS and Matlab matches and is the following :

 std_msgs/Header header
  uint32 seq
  time stamp
  string frame_id
diagnostic_msgs/DiagnosticStatus[] status
  byte OK=0
  byte WARN=1
  byte ERROR=2
  byte STALE=3
  byte level
  string name
  string message
  string hardware_id
  diagnostic_msgs/KeyValue[] values
    string key
    string value
end

I am interested in the string value array inside the KeyValue[] values bus. In Simulink this element is detected as a bus element in an array of sub-buses. I have tried many combinations of Selector blocks and Bus Selector blocks but I havent been successful in extracting this data and exporting it to the Matlab workspace.So far I have tried the following :

Any help would be greatly appreciated! Thanks in advance.

Answer 1

Hi Sorry for the delayed response.

I was able to create this, it is indeed a bit tricky with Simulink buses and able to extract the data.

>> msg =

ROS DiagnosticArray message with properties:
    MessageType: 'diagnostic_msgs/DiagnosticArray'
         Header: [1×1 Header]
         Status: [16×1 DiagnosticStatus]

Please note the three images attached, (1) The Simulink model using "Selector" + "Bus Selector" blocks in tandem, (2) The Default array sizes for the variable sized buses which are defined in the Simulink > Tools > ROS > Manage array sizes for the model.

Thanks

Robotics Team @ MathWorks

Simulink Model </matlabcentral/answers/uploaded_files/128351/2018-08-09_12-11-10.png>

Setting for Diagnostic Array: </matlabcentral/answers/uploaded_files/128352/2018-08-09_12-11-52.png>

Setting for Diagnostic Status: </matlabcentral/answers/uploaded_files/128353/2018-08-09_12-12-11.png>