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Revision to Connecting endstop switches

David Crocker

* An endstop switch with an active-low output holds the input pin at about 3.3V when the switch is not triggered, and about 0V when it is triggered. One example is a normally-open microswitch (which is not recommended, because a normally-closed switch is safer). Another example is a Hall sensor with an open-drain output that is connected directly to the Duet endstop input. The LED on the Duet will be illuminated when the switch is connected and triggered.
 
The endstop switches each need to be able to sink 1.5mA current for the Duet 2 WiFi and Duet 2 Ethernet, 0.3mA for the Duet 2 Maestro, and 2.1mA for the Duet 06 or 085. This is not usually a problem, except with some optical endstop switches that were not designed properly for 3.3V operation. Note:

'''Note:'''
some types of endstop (e.g. opto endstops designed for 5V operation) my pull the endstop input low enough to light the LED, but not low enough for the Duet to recognise that the input is in the LOW state.
The endstop switches each need to be able to sink 1.5mA current for the Duet 2 WiFi and Duet 2 Ethernet, 0.3mA for the Duet 2 Maestro, and 2.1mA for the Duet 06 or 085. This is not usually a problem, except with some optical endstop switches that were not designed properly for 3.3V operation. Note:

'''Note:'''
some types of endstop (e.g. opto endstops designed for 5V operation) my pull the endstop input low enough to light the LED, but not low enough for the Duet to recognise that the input is in the LOW state.
 
Each axis endstop input can be configured in firmware for a Max (high end of axis) or Min (low end of axis) endstop, and with an active high or active low signal level. Configuration is done in config.g using the M574 command.

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