Vehicle Network Toolbox Value Table Use

Hi, I have been decoding this CAN message using DBC file which contains meanings of each message; for example, 1 is on and 0 is off.

This information is under canDB (DBC file information) -> Message info -> signal info -> Value Table.

canDB = canDatabse (example_dbcfile)

There is a function to create a canMessageTimetable as in a timetable with only values (1 and 0) but don't see any functions or ways to create a timetable to saw (on or off) using the value table.

Is there a way to create a timetable using this value table automatically for each CAN message?

Answer 1

[Harimurali]

Hi Min,

A timetable that shows "on" or "off" instead of 1 or 0 can be created using the value table defined in the DBC file by writing a MATLAB script. The script decodes the raw data based on the value table and then creates a new timetable with the decoded values. Here is an example MATLAB script to do the same:

% Load the DBC file

candb = canDatabase("example_dbcfile.dbc");

% Assume canMsgs is a variable containing your raw CAN messages

% Create a canMessageTimetable from the raw CAN messages

canTimetable = canMessageTimetable(canMsgs, candb);

% Initialize a cell array to hold the decoded messages

decodedMessages = cell(size(canTimetable, 1), 2);

decodedMessages(:, 1) = {candb.MessageInfo.Name};

for i = 1:numel(candb.Messages)

message = candb.MessageInfo(i);

signals = canTimetable.Signals{i};

% structure to store the decoded values for each signal for a given message

sigVal = struct();

for j = 1:numel(message.Signals)

signal = message.SignalInfo(j);

rawValues = num2cell(signals.(signal.Name));

if numel(rawValues) ~= 0

decodedValues = cell(numel(rawValues), 1);

else

decodedValues = cell(numel(rawValues) + 1, 1);

end

% Check if the signal has a value table

if ~isempty(signal.ValueTable)

for k = 1:length(rawValues)

% Decode based on value table

decodedValues{k} = signal.ValueTable(rawValues(k));

end

else

% If no value table, just copy the raw values

decodedValues = rawValues;

end

% Store the decoded values in the structue

sigVal.(signal.Name) = decodedValues;

end

decodedMessages{i, 2} = sigVal;

end

% Create a new timetable with the decoded values

decodedTimetable = array2timetable(decodedMessages, 'RowTimes', canTimetable.Time);

% Add variable names to the timetable

decodedTimetable.Properties.VariableNames = [, "MessageName", "SignalInfo"];

Refer the following documentation for more information on CAN "canMessageTimeTable" and it's format: https://www.mathworks.com/help/releases/R2023a/vnt/ug/canmessagetimetable.html

[Min]

Hi Harimurali, thanks for the info! I am sorry but I forgot to take this question down since I was able to complete/solve the issue by creating a timetable based on number of messages, variable type, and automate based on variable names; then create double for loop ro run using 'valueTableText'.

Thanks for your time though! :) I will accept this as an answer and also share my code here for anyone to use.

numMsg = height(app.data); %Can be stand alone/used in all signal since the time height are the same?


data_numberofmessage = width(app.data);
data_numberofstrings = repmat({'string'}, 1, data_numberofmessage);
data_columnNames = app.data.Properties.VariableNames;

app.data_Status = timetable('Size',[numMsg data_numberofmessage],'VariableTypes',data_numberofstrings,'RowTimes',app.data.Time,'VariableNames', data_columnNames);

for ii = 2:numel(data_columnNames)
    for iii = 1:numMsg
        app.data_Status.(data_columnNames{ii})(iii) = valueTableText(canDB,"data", data_columnNames{ii},app.data.(data_columnNames{ii})(iii));
    end
end