G28 is one of the two primary “home” codes out there, but as I’ve discovered in other threads talking with Rob, this code isn’t supported yet because of the in-between work that CM does before sending code to the GRBL board, which provides a lot of intelligence that GRBL doesn’t have.
Rob has mentioned that support for G28 is forthcoming, and should be fairly easy to add.
If you’re actually seeing a “G82” in your code, that’s a canned cycle for “drilling with dwell” which I’m doubting is what you meant
Just for the forum benefit by the way, the G17/G18/G19 codes have to do with arc motion in vertical planes instead of horizontal ones. By default the machine is running all arcs in the XY plane; G17. But, the g-code can specify arcs vertically using G18 for XZ or G19 for helical or straight-arc lead-in moves.
I found this G-code reference last Friday, and it has been very helpful as I’ve been trying different post-processing settings from HSMxpress.
Edit: I will note though that GRBL does have some variation from the standard G-code, so in your MeshCAM posts and in CM logs you may see things that don’t line up to things here.