1st attempt at changing filament for 2-color printing

[wmyhal]

@Larry

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You have octoprint why not use the Control Tab type in the amount of filament in mm you want to extrude then hit the Extrude button. Works like a charm for me.

Can this be done in the middle of a pause command?

[Ender5r]

@Geit

There is a strange PIN compare in marlin code:

#define HAS_E_STEPPER_ENABLE (HAS_E_DRIVER(TMC2660) \
|| ( E0_ENABLE_PIN != X_ENABLE_PIN && E1_ENABLE_PIN != X_ENABLE_PIN \
&& E0_ENABLE_PIN != Y_ENABLE_PIN && E1_ENABLE_PIN != Y_ENABLE_PIN ) \
)

And HAS_E_STEPPER_ENABLE must be set, to use the E option in the M84. So it looks to me that some printer boards use the same X or Y enable pin on the board to enable the Extruder. So in marlin they decided “E” to only be effective, when E0 enable is not y enable and not x enable.

So disabling X or Y on such boards disables the extruder silently, too, which does no harm. Without this check disabling the extruder would also disable x or y, which could end up in a disaster.

You should be able to verify this checking the pins.h of your mainboard and compare the values.

To summarize this: This is a hardware limitation of your specific board, as the motor enable for the extruder is connected to the x or y enable and thereby cannot be used separately without effecting the linked other axis motor.

There’s a lot of logic to that explanation. What this sounds like to me is these boards (including mine I guess) have a chip on them that doesn’t have enough separate pins to provide driver logic to all 4 stepper motors. I can’t help but wonder if this is a limitation of the ATmega1284p chip.

OTOH, I can see another possibility (this is all hypothetical). I assume the ATmega1284p has to drive UART chips to carry out its instructions. What if using, say, 2 UART chips would leave the designer short by 1 pin. The company doesn’t want to pay for another UART to provide the extra needed pin. What to do? Well, what if the extruder enable/disable is tied to the X and Y UART pins? It won’t give separate control of the extruder stepper, but it will otherwise work. It would save realestate on the board and save the 18 cents it costs for another UART chip. Like I said, this is hypothetical, but it’s the kind of discussions that take place every day in design & manufacturing. I’m sure Irv would agree.

[Larry]

@wmyhal

Can this be done in the middle of a pause command?

Yes anytime it just sends the correct Gcodes to the printer. I use it all the time when paused.

[wmyhal]

@Larry

Yes anytime it just sends the correct Gcodes to the printer. I use it all the time when paused.

Then this is a good solution. Ill give it a try. Thanks