Getting dlc not set to 8 as expected when using client.session(1)

[Nishanth-cts]

Hello Pylessard, after setting isotp parameters for vn1640a, and trying to enter into default session using client.session(1) in my canalyzer trace I see I get dlc is not set to 8 as expected and hence response to my 10 01 request I am unable to see. Could you kindly let me know where I am going wrong?

[Nishanth-cts]

Attached above are the isotp, client configuration as well as uds request sent.

[pylessard]

@Nishanth-cts
First of all stop sending pictures of your screen. Just copy paste the relevant piece of code.

Second, DLC of 8 is not required. If you want a dlc of 8 bytes, you can set a tx_data_min_length parameter.

Also, you are making very reckless usage of threads. Running a thread that reads you can box may deplete the internal buffer and stop messages from reaching the isotp stack. You can add a listener that prints instead of using a thread.

You should also read about threading.Event object. Instead of using a global variable and doing sleep(1). You can just do event.wait() in your isotp thread and event.set() in your tkinter thread. It will react in microseconds and avoid bloating your cpu.

[Nishanth-cts]

Hello Pysellard,
Thanks for the valuable input it seems that now i am able to send the diagnostic request. But, when

i am trying to send 22 40 B5 request using client.read_data_by_identifier(0x40B5) I get a config error saying that 40B5 DID is not found. Could you kindly let me know how to handle read data by identifier such that I can send my own DID's to be read?. Attached below is the code snippet:

[pylessard]

I wrote an extensive documentation. Please read it

https://udsoncan.readthedocs.io/en/latest/udsoncan/examples.html#reading-a-did-with-readdatabyidentifier
https://udsoncan.readthedocs.io/en/latest/udsoncan/client.html#udsoncan.client.Client.read_data_by_identifier

[Nishanth-cts]

Hello Pylessard,
Thanks very much it works. I just have one last question. When i try to First enter into default session using client.change_session(1) followed by client.change_session(3) I only see response for 10 01 but not for 10 03.
Could you kindly let me know how to handle such scenarios where consecutive UDS requests have to be sent.