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For my own interest I'm looking at data logging OBD2 data. Yes I have scan tools that can do the job but want more such as recording the commands as well as data. I see there are data loggers for under $200 but I have read about so called free software but can't find any. I think they give you the software (for free) when you buy their tool. Any advice on how to go about it will be much appreciated.

What data do you want to log? If its just SAE pids then everything is pretty well known. If you want to dive in to proprietary finding pids is the harder part. If you want to use a Y piece and monitor bus traffic then probably universal patchers J2534 logger is the go, with a 3rd party tool such as some android app with an elm on the same bus as your J2534 tool.

The main thing is canbus activity. One of my cars reports canbus errors but only with 1 out of 3 scan tools and suffers no consequences and no code light so I figure it's time I started improving my knowledge in this area and delving into the deep.

Ok then use universal patchers J2534 console to monitor the bus with any J2534 tool, or the AVT tool if you have one of those and see what you can see. You have to do some amount of protocol setup and connect then you should see whatever the interface sees. use a Y connector and other interface if you need something to get the traffic moving or to generate the traffic to monitor. The 'buffer' toggle can be needed if you hit the computers speed limits and you can use the filters as well if there is too much traffic on the bus to be useful.

Thanks antus. Looks plausible even for me with limited knowledge to start playing around. It's just an interest thing to start to get a handle on whats happening.