Duet mainboard and expansion boards support a variety of endstop sensors. This page covers connecting and configuring mechanical switches (eg microswitches), Hall sensors and optical endstops.
Connect your endstop to the Duet, following these board-specific notes:
Endstop devices can be connected to the IO_0 through IO_9 connectors. Each endstop input has a 27K pullup resistor, so the endstop devices only need to sink 0.12mA.
Maximum input voltage on IN pin: 30V
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.
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 active-high or active-low output:
The endstop switches each need to be able to sink 1.5mA current for the Duet 2 WiFi and Duet 2 Ethernet. 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) may 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.
Duet 2 WiFi/Ethernet hardware rev 1.04 and later: 8.3V. Higher voltages may damage the endstop LED.
Duet 2 WiFi/Ethernet hardware rev 1.03 and earlier: 3.3V (in practice a little more is unlikely to damage the Duet)
Duet 2 series has endstop labels with axis names. The following table shows a conversion between axis names and numbers of all available endstop inputs. In RRF 2.x the endstop mapping is fixed; endstops cannot be reassigned. If you reassign the X axis to a different stepper driver with M584, x_stop will still be the X endstop connection.
| Number | Name | Comment |
|---|---|---|
| 0 | X | |
| 1 | Y | |
| 2 | Z | |
| 3 | E0 | |
| 4 | E1 | |
| 5 | E2 (E2_STOP) | Expansion Header/DueX2/5 |
| 6 | E3 (E3_STOP) | Expansion Header/DueX2/5 |
| 7 | E4 (E4_STOP) | Expansion Header/DueX5 |
| 8 | E5 (E5_STOP) | Expansion Header/DueX5 |
| 9 | E6 (E6_STOP) | Expansion Header/DueX5 |
| 10 | Stop 10 (ENC_B) | CONN_LCD Header |
| 11 | Stop 11 (ENC_A) | CONN_LCD Header |
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 (same pinout as for the Duets covered in the previous section).
There is no LED provided, just a 10K pullup resistor. So the endstop devices only need to sink 0.3mA.
Maximum input voltage on STP pin: 30V
Duet 2 series has endstop labels with axis names. The following table shows a conversion between axis names and numbers of all available endstop inputs. In RRF 2.x the endstop mapping is fixed; endstops cannot be reassigned. If you reassign the X axis to a different stepper driver with M584, x_stop will still be the X endstop connection.
| Number | Name |
|---|---|
| 0 | X |
| 1 | Y |
| 2 | Z |
| 3 | E0 |
| 4 | E1 |
In the following descriptions, STP/IN refers to the IN pin of the connector if you are using a Duet 3, otherwise to the STP pin of the connector.
This applies to a bare microswitch, not to a microswitch on a board with a LED.
We recommend you use the normally-closed contacts of the microswitches, which are generally the outside two connections on the microswitch.
RepRapFirmware 3.x: Set the endstop type to switch (S1) in the M574 command. If you use normally-open microswitch contacts, invert the polarity by putting a ! character at the start of the pin name in the M574 command.
RepRapFirmware 2.x and earlier: Set the signal polarity to active high (S1) in the M574 command. If you use normally-open microswitch contacts, then you will need to set the signal polarity to active low (S0) in the M574 command.
Wires connecting normally-open endstop switches are susceptible to capacitive interference pickup, in particular from nearby stepper motor cables but to a lesser extent from heater and fan cables. You can mitigate this to some extent by using lower value pullup resistors. A better solution is to change to normally-closed endstop switches if possible, or to use shielded cable to connect the normally-open endstop switch.
Connect it to the Duet endstop connector as follows. Note: the pins on the Duet endstop connector are not in the same order as on RAMPS!
| Makerbot endstop pin number | Function | Duet 3 IO_x pin marking | Duet 2 endstop pin marking |
|---|---|---|---|
| 1 | VCC | 3V3 | 3V3 |
| 2 or 3 | GND | GND | GND |
| 4 | Output | IO_x_IN | STP |
Unfortunately the pin markings on the Makerbot endstop board are hidden underneath the connector. Pin 1 is next to the long edge of the board that does not have the microswitch on it, and pin 4 is nearest the edge with the microswitch.
These devices produce an active-low output. If using RepRapFirmware 3.x, invert the polarity by putting a ! character in front of the pin name. If using RepRapFirmware 1.x or 2.x, use the S0 parameter in your M574 command.
Connect Gnd to Gnd, Vcc of the Hall sensor to 3V3, and the output of the Hall sensor to STP/IN. Simple Hall sensors normally have active low outputs, so put ! at the start of the pin name if using RRF 3.x, or use S0 in the M574 command if using RRF 1.x or 2.x.
If your Hall sensor is a circuit board with a sensitivity adjustment potentiometer on it, then it may provide an active high output instead of active low. If your hall switch is just the IC then you should also connect a 0.1uF capacitor between Vcc and Gnd close to the IC.
Examples: Allegro A3141, A3142, A3143, A3144 (all of these are discontinued products, but still found on eBay)
Duet 3: as for 3.3v Hall sensor, but connect Vcc to the 5V pin of the IO_connector instead of the 3.3V pin.
Other Duets: Preferably, use 3.3V-compatible Hall sensors instead. However, If your 5V Hall sensor has an open-collector or open-drain output (as the devices listed above do), or if you are using a Duet WiFi/Ethernet hardware rev 1.04 or later or a Duet Maestro, you can wire it as for a 3.3V sensor except that Vcc must be connected to +5V (available at pin 1 of the expansion connector) instead of to the 3v3 endstop connector pin.
Connect Gnd to Gnd, Vcc of the opto sensor to 3V3, and the output of the opto sensor to STP/IN. Opto sensors usually have active high outputs, so in RRF 3.0 and later set the endstop type to switch (S1) in the M574 command. In RRF 2.x and earlier, also use S1 in the M574 command, though this sets the endstop as have active high input.
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. Here are some workarounds:
RepRapFirmware only supports one endstop per motor per axis. If your axis only has one motor, you can only have one endstop. If your axis has two or more motors, you can have an endstop per motor, if the motors are plugged into their own stepper driver, and the motors can be homed individually to their own endstop. To do this, see the 'Axis levelling using endstops' section of Bed levelling using multiple independent Z motors
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.
On most types of printers except delta, you do not need to have a Z endstop switch if you use a Z probe for Z homing.
Example of a simple endstop configuration, with X and Y microswitch endstops on the low end (X1 and Y1), using switch-type endstops (S1) on appropriate pins. Z also has the endstop at the low end (Z1), but has the Z probe configured as the endstop:
Duet 3:
; Endstops
M574 X1 S1 P"io1.in" ; configure switch-type (e.g. microswitch) endstop for low end on X via pin io1.in
M574 Y1 S1 P"io2.in" ; configure switch-type (e.g. microswitch) endstop for low end on Y via pin io2.in
M574 Z1 S2 ; configure Z-probe endstop for low end on Z
Duet 2:
; Endstops
M574 X1 S1 P"xstop" ; configure switch-type (e.g. microswitch) endstop for low end on X via pin xstop
M574 Y1 S1 P"ystop" ; configure switch-type (e.g. microswitch) endstop for low end on Y via pin ystop
M574 Z1 S2 ; configure Z-probe endstop for low end on Z
Example of a simple endstop configuration, with X and Y microswitch endstops on the low end (X1 and Y1), using active-high endstops (S1) on appropriate pins. Z also has the endstop at the low end (Z1), but has the Z probe configured as the endstop:
; Endstops
M574 X1 Y1 S1 ; set active high endstops
M574 Z1 S2 ; set endstops controlled by probe
For more detail on specific types of printers see:
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. You can also run M119 from the console in DWC, if you don't have the endstop status available.
Early versions of DWC (v1.x, v2.x) displayed the endstop status in DWC. This was removed in DWC v3.0. As of DWC v3.3, you can install the Endstops Monitor plugin if you need it; see Duet3D github repository here for the latest version.
Note: the following does not work if you are using stall detection instead of wired endstops.
In the Endstops or Endstop Hit column you can see the state of each endstop.