One of the best tutorials (if not the best) in this community forum is:
If you want, you can use mysql persistence to store the item values over time. Then you would need a graphing "solution" to display the stored date. I am not sure if Grafana can link to a mysql db and query data from there... you could try that also.
In general: A persistence service will store the values from selected items on predefined intervals that you specify.
It doesn't really matter what the items are bound to (they could be KNX binding based or serial binding based, etc, etc). The value of the item gets persisted, so if you get your item working, you will then be able to store that value in a db (and then, use or graph the data).
Check out these threads also: