Once only per unit, follow the instructions here:
https://www.waveshare.com/wiki/2-CH_CAN_FD_HAT
Create a python virtual environment:
python -m venv .venv
Activate it
. .venv/bin/activate
Install the python modules:
pip install python-can can-isotp udsoncan
For typical automotive powertrain ECUs, the CAN bitrate is 500k and the CAN-FD data bitrate is 2M:
sudo ip link set can0 up type can bitrate 500000 dbitrate 2000000 restart-ms 1000 berr-reporting on fd on sudo ifconfig can0 txqueuelen 65536
For first simple dumping of messages:
candump can0
Once the virtual environment is installed and activated, you can see the activity on the CAN bus with can_viewer.py:
can_viewer.py -i socketcan -c can0 -b 500000 --fd --data_bitrate 2000000
This shows all messages, including those you transmit. When yo are scanning, you might not want to see everything you send, viewer_mjt.py has a quick hack to only show received messages. Also, canmon.py in this repo just shows each CAN ID once, which can be handy.
From the command line you can do
cansend can0 000#11.22.33.44
to send on id 000 with 4 data bytes.
In this repo, firstcan.py is a quick hack for sendign a variety of conection messages on many different IDs in order to find which one the ECU responds to. It sends on a range of IDs with various CAN frame padding schemes (some ECUs do not respond if the padding is not what they expect). It also sends at a lower-than-saturating rate, as some ECUs are not able to throw messages away fast enough, and will miss the one you hoped they would respond to.
Scanning the first 11-bit range takes a few minutes. Scanning the whole 29-bit range will take a week or so...
once you find an ID pair on which the ECU listens/resopnds, you can build on USONCAN:
https://udsoncan.readthedocs.io/en/latest/udsoncan/examples.html