M302 description incorrect

[thinkyhead]

The source code for M302 states:

case 302: // M302 S<0 or 1> - allow cold extrusion.
          // Without S parameter it will allow. S1 will disallow.
    Printer::setColdExtrusionAllowed(!com->hasS() || (com->hasS() && com->S != 0));
    break;

• "Without S parameter, it will allow." Correct: !com->hasS()
• "S1 will disallow." Wrong: com->hasS() && com->S != 0

According to the code, S1 will actually allow cold extrusion, not disallow it. (The same as RepRapFirmware's "P" parameter, but the exact opposite of Marlin.)

I'd like to see this command applied consistently, if possible. In Marlin 1.0.x the behavior is:

• M302 S0 allows cold extrusion (by setting the min extrusion temp to 0)
• M302 by itself allows cold extrusion (exactly the same as S0)
• M302 S180 disables cold extrusion below 180 (celsius only in 1.0.x)

I'm proposing to extend Marlin's M302 (MarlinFirmware/Marlin#4222) with the following changes:

• M302 by itself displays the current cold extrusion status (RepRapFirmware).
• M302 P1 allows cold extrusion (RepRapFirmware).
• M302 P0 disallows cold extrusion below the current min extrusion temp (RepRapFirmware).
• M302 S180 P1 sets the min extrusion temp to 180, but allows cold extrusion.

[luc-github]

good catch
actually come from repetier : https://github.com/repetier/Repetier-Firmware/blob/development/src/ArduinoDUE/Repetier/Commands.cpp#L2057-L2058

you can open ticket to them or will do - let me know

About improvement of command I also suggest to propose to repetier original FW for consistency

[thinkyhead]

Oops, I did mean to post it on the main page, but I was poking around here. Thanks!

repetier/Repetier-Firmware#548

[luc-github]

👍