How can I use the blfread function with a database containing multiplexers?

Hey everyone,

I am currently processing CAN traces including OBD2 messages, the "blfread" function from the Vehicle Network Toolbox has always worked quite well, but I now have a OBD2 database which contains multiplexers. When I use the function the signals are not decoded as desired and the result is the same as when I don't assign a database. Does anyone have an idea to solve the problem or know of another function that can handle this?

candb = canDatabase('OBD2_database.dbc'); % Load database containing multiplexer
data_obd = blfread('Trace_OBD.blf', "Database", candb); % load the trace file and decode with database

This shows the resulting table without multiplexer, in the struct in Column 6 are the Signals decoded.

This shows the resulting table with multiplexer, there is an empty struct in Column 6.

I can see a difference in "candb" after loading between the file with (upper) and without (lower) multiplexer. As you can see in the pictures, the Data Inspector shows that with the multiplexer there is an additional Struct layer, which apparently prevents decoding.

Answer 1

[Qiang Sun]

You can first try to read the blf file, and then find the ID and the corresponding multiplexer information (usually the first byte in the Data field),Based on this information, rename the ID to the mapped ID and save the file. Finally, use the dbc with the mapping ID to parse the new blf file.

Reference code:

blfData = blfread('old_blf',1,"CANStandardFilter",hex2dec('6B2'));% ID,0x6B2

uu=cell2mat(blfData.Data);

vv=uu(:,1);

ww=blfData.ID;

for i = 0:255

blfData. ID(find(vv == i & ww == hex2dec('6B2')))= i + hex2dec('700'); % Mapped ID=the first byte in the data field+0x700

end

blfwrite("new.blf",blfData,1,"CAN");

blfData = blfread('newfile.blf',1,"Database",canDatabase('database_with_mapped_ID'));