GPIO, Fan tacho and print cancelation

  • This is a two-in-one question.

    1. On the Connecting and Configuring fans-Page it is described how to connect the tacho-signal of a fan

    Tacho wire (whatever wire is left, usually green or yellow): optionally, connect it to the cathode of a small signal diode (1N4148 should be OK) and connect the anode of the diode to pin PB6 on the expansion connector if the Duet WiFi/Ethernet, to provide a reading of the fan RPM.

    The gcode documentation to M950 does not mention which ports are usable for the tacho signal.

    May I only use pb6 for the tacho signal of a fan, or are other (GPIO-)pins also usable? (I am using a Duet2Ethernet + Duex5)

    If pb6is the only usable pin for this, how can I feed the tacho-signal of more than one fan into the duet board?

    1. A fan failure will most probably cause a failed print, maybe a cloggend heatsink and maybe more damage to the printer. What is the way to make the printer stop if a fan fails?