in the marlin RC, there are sections for "Filament Runout Sensor" and "FILAMENT_WIDTH_SENSOR"
looking for filament movement sensor, I'm not seeing news on that front for over a year, dec 2015. the movement sensor requires a wheel against the filament to detect movement. using a bowden setup for the second extruder, this may a lot less likely to happen on that side as it would have to be before it enters the bowden side extruder. The only other place I could think to put it would be in the hole on the bondtech. on the direct driven side, it has to be installed before it goes into the PTFE tubing. This sensor also is going to put more load on the motion controller as well. because the sensor will send in a signal and the motion controller has to verify if it is a false positive. For instance, is the second extruder moving while the first is stopped.
This also brings up another possibility. If you installed filament movement sensors on the extruder, below the stepper motors, it might raise them high enough up to place the motors facing out to the sides, allowing for 2 direct drive extruders using a bondtech design. very complicated though. But then you have the added weight back on the extruder.
FILAMENT SENTINEL looks to be a runout sensor, not a movement sensor.
With what I know now about the back and forth talk to the motion controller and the touchscreen, you are not likely to get a pause, but a print restart from the point that the motion controller tells the touchscreen that it has a problem, aka filament runout. the potential issue here is that the print may be misaligned when it resumes. The good news is that the touchscreen will know exactly where it stopped.
I need to do some testing on the emergency parser but not sure it is implemented for everything yet.
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