milhead2
Not so much an issue....
Is it possible to use your library to decode DM1s from a BLF file recorded with Vector tools?
Do you have any examples of doing this?
Hu Dan,
I don't have any code to convert a .blf capture from the vector tools but I believe that Brians python-can (https://python-can.readthedocs.io/en/master/) can convert the log to an ascii format for you. Specifically look at https://python-can.readthedocs.io/en/master/listeners.html#blf-binary-logging-format
Once you have an ascii dump decoding DM1 messages is pretty simple but pretty much you just follow the DM1 PGN definition in j1939-73 (5.7.1)
Happy decoding!
Miller
From: tractorDan @.> Sent: Wednesday, October 6, 2021 3:20 AM To: milhead2/python-j1939 @.> Cc: Subscribed @.***> Subject: [milhead2/python-j1939] Not so much an issue.... (#16)
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Is it possible to use your library to decode DM1s from a BLF file recorded with Vector tools?
Do you have any examples of doing this?
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Thanks for the response - I'll look at that.
The main problem is that, if a DM1/FECAh is 8 bytes or less, it shows up as a FECAh with 8 bytes of data following (in a Vector log). However, if the DM1 is longer than 8 bytes, it no longer shows up as an FECAh with n bytes of data; you have to, instead, decode the "multi-packet" transport protocol messaging used, instead.
I wondered whether there was a J1939 library for Python that can automatically 'reconstruct' these TP messages into a DM1 so they always appear as an FECAh message with 8 or more data bytes.
Also, some of the log files I'm looking at are 20GB in size; converting to ASCII would be problematic, I think. I'll give it a try, though.
Thanks again.
Hi Dan,
You are correct, I forgot about the BAM and CTS/RTS packaging that j1939 provides. In my company we rarely see more than a single fault in a DM1 and I flat out forgot about it.
There is a logger example app that you may be able to fool with but I don't in python-j1939 have any built in capability to read CAN data from any source other than a python-can library below me.
If I were doing it I would be to look at the logger example app application and figure how to write a moc for the python-can interface that feeds the protocol layer the raw can packets. There are only a few moc methods that you would need to write.
Hope that helps..
Miller
From: tractorDan @.> Sent: Wednesday, October 6, 2021 11:14 PM To: milhead2/python-j1939 @.> Cc: Miller Lowe @.>; Comment @.> Subject: Re: [milhead2/python-j1939] Not so much an issue.... (#16)
External Email Think Before You Click.
Thanks for the response - I'll look at that.
The main problem is that, if a DM1/FECAh is 8 bytes or less, it shows up as a FECAh with 8 bytes of data following (in a Vector log). However, if the DM1 is longer than 8 bytes, it no longer shows up as an FECAh with n bytes of data; you have to, instead, decode the "multi-packet" transport protocol messaging used, instead.
I wondered whether there was a J1939 library for Python that can automatically 'reconstruct' these TP messages into a DM1 so they always appear as an FECAh message with 8 or more data bytes.
Also, some of the log files I'm looking at are 20GB in size; converting to ASCII would be problematic, I think. I'll give it a try, though.
Thanks again.
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