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Revision to Connecting endstop switches

David Crocker

Each endstop input has ground, +3.3V and sense pins in that order, labelled GND, 3V3 and STP respectively on the back of the board.
 
EachOn all Duets except the Duet 2 Maestro, each input has a pullup resistor and red LED between the STP pin and +3.3V. The LED will be illuminated when an endstop switch or other device connected to the input holds the voltage close to 0V (ground). '''Whether the LED is illuminated when the endstop switch is triggered or not triggered depends on whether your endstop switch produces and acive-highactive-high or active-low output:'''
EachOn all Duets except the Duet 2 Maestro, each input has a pullup resistor and red LED between the STP pin and +3.3V. The LED will be illuminated when an endstop switch or other device connected to the input holds the voltage close to 0V (ground). '''Whether the LED is illuminated when the endstop switch is triggered or not triggered depends on whether your endstop switch produces and acive-highactive-high or active-low output:'''
 
* An endstop switch with an active-high output holds the input pin at about 0V when the switch is not triggered, and about +3.3V when it is triggered. A typical example is a normally-closed microswitch. The LED on the Duet will be illuminated when the switch is connected but not triggered.
* 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: 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: 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.
 
If you don't have access to your Duet from a browser, you can send M119 commands from USB or PanelDue to read the endstop state while doing the tests listed above.
 
=== Endstop LEDs on the Duet ===
 
Each endstop input on the Duet has an associated red LED. The LED will be lit when the endstop minput is in the LOW state. Whether LOW corresponds to the endstop being triggered or not triggered depends on the type of endstop:
 
* If the endstop input is active high (e.g. normally-closed microswitch, or optical endstop) then the LED will light up when the endstop is connected but not triggered.
* If the endstop input is active low (e.g. normally-open microswitch, or typical Hall effect sensor) then the LED will light up when the endstop is connected and triggered.
 
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.

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