Add M850 code for setting sheet label and offsets

[vintagepc]

Per #2091 and #2153
This adds M-code support for reading and setting sheet labels and offsets to satisfy advanced user needs. Logic being, if you know how to manually send g-codes to your printer, you're advanced enough to handle the responsibility.
I chose 850 because it's near other first-layer/levelling parameters and appears to be unused in official marlin as well.

Usage:

• M850 S[sheet] Z[offset] L[label] B[Bed temp] P[PINDA temp]
• Z and L are optional, if one or both are missing the current values are reported instead.
• If L and/or Z are specified, the sheet's values are updated.
• Z range is validated
• Sheet index is validated
• Requesting info (no L or Z) on an uncalibrated sheet reports as such.

Note: Pronterface capitalizes anything sent. To use lowercase in your sheet names you'll need to use a different terminal program.

Closes #2091
Closes #2153
Closes #3534

[vertigo235]

ah, cool!

[DRracer]

@vintagepc very well ;) . Btw. there is already an M851 for setting z-offset: http://marlinfw.org/docs/gcode/M851.html - which in our terminology is live-adjust-z, aka sheet calibration value.
Do you see fit using/improving the M851?

[vintagepc]

@DRracer 🤦‍♂ Not sure how I missed that when looking for available gcodes. I'll update it to be M851 instead.

Also I see I left in a magic number in reading the sheet name; I'll change the 7 to a sizeof() too.
Can I ask what the intent of the additional sheet struct fields is? (bed temp, e.g.) I don't think they are currently used but I'd be happy to implement ability to specify those if it is planned to be relevant.

[DRracer]

@vintagepc don't worry, such things happen ;) .
The temperature will be used right away, we are preparing another long awaited/requested feature. Stay tuned ;)

[vintagepc]

OK, I'll add optional arguments for those as well then.

[vintagepc]

Looking at the code, M851 doesn't look like something I want to interfere with; that sets cs.z_probe_offset which is something entirely different from the live Z value, and used in some critical places (MBL, for example). My printer has it currently set at -0.40. If I'm reading that right it is a correction factor applied to the distance of the nozzle below the edge of the PINDA (e.g., "zip tie" distance).

Edit: To clarify, the firmware has 851 already implemented, as
case CUSTOM_M_CODE_SET_Z_PROBE_OFFSET:

[vintagepc]

(Updated to support B/P parameters for pinda and bed temp)

[vintagepc]

Syncronized with latest MK3

[bbernhard]

Hi,

I just wanted to ask about the state of this PR here. I've already seen at least two open pull requests regarding a new gcode command, but unfortunately both of those seem to be stalled. As I am also a maintainer of several open source projects myself, I totally understand that there's only so much time to work on all the bugs and feature requests. But as the Prusa printers have such a nice sheet management system I would really love to see that somehow exposed via gcode - I think it opens a LOT of possibilities for automation and convenience features.

So, I wanted to kindly ask whether there's any chance to a feature like this merged?

Many thanks,
Bernhard

[3d-gussner]

Old but good

[aaronevers]

Help article "Prusa-specific G-codes" needs to be updated with the M850 documentation (https://help.prusa3d.com/article/prusa-specific-g-codes_112173).