[FR] Cold extrusion collaboration with M302

[Tannoo]

Is your feature request related to a problem? Please describe.
Trying to test the stepper direction upon a wire replacement and new terminations, the TFT is preventing cold extrusion. M302 P1 disables cold extrusion prevention in Marlin, but the TFT will not allow this. Setting M302 S0 to allow extrusion at any temp, the TFT will not allow less than 20 deg.
https://marlinfw.org/docs/gcode/M302.html

Describe the solution you'd like
Remove the min temp setting entirely, or co-exist with M302 settings, give an option for disabling the cold extrusion monitoring (maybe even temporarily?)

Describe alternatives you've considered
Marlin mode works just fine and allows M302 to work as intended. The Touch screen mode does not.

Additional context
Would like to have consistency. Would love to not have to go to marlin mode to do anything. (Meaning to remove those EXP cables entirely.)

[Tannoo]

I tried to lower the min temp to -50 to get this setting out of the way of M302. Not having any luck.

In config.h:

#define MIN_TOOL_TEMP           -50  // extruder temp less than this will not be parsed.

I got the TFT now telling me to heat the hotend to 65486!! LOL I guess it is not a floating number and the -50 has rolled under and back over.

[Tannoo]

My T0 is not connected yet. Because of that, it's report temp is -29.
Marlin lets me test the extruder motor by disabling the cold extrusion via M302 P1, or setting the monitoring temp to 0 (M302 S0) or just click PROCEED when Marlin gives an error about the extruder is too cold.

The TFT doesn't honor it have any options.

[Tannoo]

Here is some backstory for some context.

I have a new Anycubic Kobra Max printer.
I got fustrated with the hacked Marlin firmware that is only compilable via Keil uVision programing software.
The fustration is wanting to customize the firmware options and some were removed or just didn't work. It is also based on 2.0.1. Marlin is well beyond that now.

So, I have decided to change the mainboard to an SKR 3 EZ. This required re-wiring and re-terminating just about everything.
Also had to add a BTT TFT35 E3 V3.

I got the Y motor tested before running the wires for the other motors. Testing what I can as I go. Most has been done via the TFT touch mode.

I am currently still getting the toolhead terminated and will be testing those options soon. Like the heater and thermistor. Then the BL Touch that I am adding.

[petaflot]

I confirm this is an issue. Also, display uses 180°C as a safe temperature but it is set to 170°C in firmware. Disabling the check with M302 P1 (through serial, confirmed with M302: "Cold extrudes are enabled") is ignored by the display

[rondlh]

Check the Cold Extrusion section in your TFT config.ini. The TFT is not aware of the cold extrusion setting in Marlin, I don't think it is reported. The default minimum extrusion temperature set there is 180 degrees, which is active independent of what you setup in Marlin. You can lower the temperature there as requried.

#### Cold Extrusion Minimum Temperature
# Minimum temperature needed to extrude/retract.
# Any extrusion/retraction below this temperature will be prevented.
#   Unit: [temperature in °C]
#   Value range: [min: 20, max: 1000]
min_temp:180

[petaflot]

@rondlh yes it is reported, just issue M302 and it will tell you if cold extrudes are enabled and what is the temperature threshold.

[Tannoo]

And.... I have moved on to Klipper.

[Tannoo]

That means I do not have touch screen support yet. That I have found out anyway.

[rondlh]

@rondlh yes it is reported, just issue M302 and it will tell you if cold extrudes are enabled and what is the temperature threshold.

OK, I see, and it's fully configurable within Marlin, so the TFT should be able to follow Marlin's behavior.
https://marlinfw.org/docs/gcode/M302.html
No mention of when this command was introduced. Let me investigate...