I have two medium sized, well tuned multicopters, both powered by Arducopter 3.5. I would like to switch to 4.0. Will the parameters, especially PIDs, be correctly recognized and transfered? Is there anyone who jumped from 3.5 to 4.0?
I think it should be fine but you will probably be prompted (by the pre-arm checks) to re-do the compass calibration. The PIDs and other parameters should all be upgrade as required.
I’d probably jump to Copter 3.6.12 first and compare updated parameters with saved parameters from 3.5. There is renaming of some params but there shouldn’t be any changes to PIDs. There’s Loiter improvements so probably check the new Loiter params are what you expect. Always check battery and failsafe settings.
See how that goes and if you have any issues or not.
My opinion is the next jump will be to 4.0.2 when it’s officially released.
In some upgrades, there are parameters that are not transferred or are reset to a default. The only one I know of for sure is RCFEEL when it changed to ATC_INPUT_TC - there’s a conversion in place but not for Channel 6 tuning, so check all that if you use it.
In the code check from about line 1014 onwards for the conversions: