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Revision to Connecting endstop switches


Note: opto endstops made to the Generation 7 design are often claimed to be 3.3V-compatible, but in fact the design is marginal with a 5V supply and frequently doesn't work at all on 3.3V. To use this design with a 3.3V supply, you may need to replace the 180 ohm resistor by 100 ohms, and either replace the 1K resistor by 10K or remove it completely.
== Test endstop switches ==
=== Testing endstop switches using the web interface ===
* Apply power to the printer. You need only 5V power for this test, so we suggest you leave the main power turned off and just connect the printer to a PC via the USB cable. Note: if you have a PanelDue with 7" screen then USB power may not be sufficient.
* Connect to your printer from a web browser
* Select '''Settings''' from the menu on the left hand side
* Select the '''Machine Properties''' tab
* You will see several rows of data. In the '''Endstop Hit''' column you can see the state of the selected endstop type. The first three rows in that column correspond to the X, Y and Z endstops in that order.
* If you are using conventional microswitches or sensors connected to the endstop inputs of the Duet, test that the Endstop Hit value displayed is '''No''' when the corresponding axis is not pushed against the endstop, and '''Yes''' when it is
What might go wrong:
* If the Duet fails to boot up with the endstops switches connectors, or if it disconnects from the browser as soon as you trigger an endstop switch, this usually means that you are using microswitch endstops and you have connected to the wrong pins of the endstop connector. 2-wire microswitches must be connected to the outer two pins of the connector, which is not the same as many other 3D printer control boards.
* If the endstop switches read in reverse, then the remedy depends on the type of endstop sensor:
** If the sensor is a 2-wire microswitch, we recommend that you use the normally-closed contacts, which are the two outermost tags on the switch (leave the centre tag not connected).
** If you are already using those contacts, or you are using a different type of endstop sensor, in the M574 command in config.g change S0 to S1 or vice versa.
* If the Endstop hit value doesn't change when you trigger the endstop:
** Check the wiring
** If they are optical endstops, first make sure that you have S1 in the M574 command. Then, if the endstops show as triggered all the time, your endstops are probably ot 3.3V compatible and you need to modify them - see [[Connecting_endstop_switches#3.3V-compatible_optical_endstop]]. If they never show as triggered, check that the flag on the end of the axis blocks the slot completely, and that there is a pullup resistor between the sensor output and +3.3V (10K is usually suitable).
=== Testing endstop switches using M119 ===
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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