The Duet 3 Mainboard 6HC is a next-generation controller board that builds on Duet3D's experience in developing the most flexible 3d printer control solutions. It is the core of the Duet 3 family which provides control for a wide range of machines including 3d printers, CNCs, lasercutters and more. The overall aim with the Duet 3 series is to allow for maximum flexibility of machine design through highly capable mainboards, expansion boards, smart tool boards and custom expansion modules. The flexibility of configuration and advanced features are enabled by our innovative RepRapFirmware running on the Mainboard and DuetSoftwareFramework running on the single board computer.
The Duet 3 Mainboard 6HC is the first version of the Mainboard produced.
The main hardware features of the Duet 3 Mainboard 6HC are listed below.
|Processor features||300MHz ARM Cortex M7, 1Mb flash, 384Kb RAM, hardware floating point (double precision), DMA, 32Kb cache|
|Networking/Comms||10BaseT/100BaseTX Ethernet, or via attached SBC; USB port; serial port; CAN-FD bus|
|On-board stepper drivers||6 x TMC2160|
|Stepper driver features||Up to 6.3A peak current, microstep interpolation from any setting to x256, stall detection, stealthChop2|
|High current outputs||1 x 15A1, 3 x 6A each|
|Thermistor/PT1000 inputs||4 x inputs, optimised for 100K thermistors and PT1000 sensors|
|Medium current outputs||6 x PWM-controlled outputs, of which 3 support tacho input. Voltage selectable between VIN / 12V / external power, in 2 banks. One VIN-voltage, always-on output.|
|Inputs/Outputs||9 x on-board I/O connectors for endstop, filament monitor, Z-probe, hobby servo or PanelDue connection. Inputs are 30V-tolerant. Also one output with 5V signal level for hobby servo, laser control or VFD.|
|Power monitoring||VIN voltage monitoring allows for state save on power failure.12V regulator output voltage also monitored|
|SD card interface||On-board high speed SD card socket.|
|Support for attached Raspberry Pi or other Single Board Computer (SBC)||Yes|
|External stepper driver support||Via CAN bus|
|Stepper driver expansion||20+ via CAN-FD-connected expansion boards|
|High current output and/or thermistor expansion||20+ via CAN-FD-connected expansion boards|
|PT100 and thermocouple daughterboard support||Supports 2 x daughterboards (4 channels) on board. 50+ via CAN-FD-connected expansion boards.|
|LCD support||Typically provided by HDMI touch screen attached to the SBC. PanelDue also supported.|
|LED strip support||RGB Neopixel (max. 60 LEDs) or DotStar|
|Other expansion||A huge variety supported via CAN-FD-connected expansion boards|
|1 Note that the board is rated to 18A on the '15A high current output'; however it is supplied with a 15A fuse fitted (18A are difficult to source). If you need 18A on the this output then you need to fit a 20A fuse and take further precautions against over-current.|
|Stepper drivers||Up to 6.3A peak current|
|High current outputs||OUT0 up to 18A (see note above), OUT1/2/3 up to 6A each|
|Input power voltage||11V to 32V for VIN, 0V to 32V for OUT0|
|Inputs/Outputs||Inputs are 30V-tolerant|
|Input connector rated current||25A maximum, or fused limit (whichever is lower)|
|Fuses||15A for V_Fused, 15A for OUT0.|
|5V current limit||3A total on 5V and 3.3v, including the internal current consumption (around 200-300mA), any PanelDue or other display, and any endstops/Z probes that draw significant power, and any connected SBC powered by the Duet.|
|12V current limit||800ma (fan pins only, when 12V selected)|
For firmware update instructions when running in stand-alone mode, see Installing_and_Updating_Firmware. If running from an SBC, see the 'Updating Duet 3 mainboard firmware' on this page: Getting Started With Duet 3 MB6HC.
Importantly Duets are Open:
See the Hardware overview page for a feature comparison table between different versions of the Duet.
On Duet 3 Mainboard 6HC the mounting holes are isolated and not plated through, they have a keep out area around the M4 clearance hole of an additional 2.2mm radius. Any metallic mounting solution should keep inside this keep-out area.
In many applications passive cooling will be sufficient, especially if the board is mounted vertically in a well ventilated position. If active cooling is needed then a fan blowing across the back of the board along the line of the stepper drivers is recommended.
The stepper drivers' heatsinks are connected to the PCB and the majority of the heat is dissipated via the PCB so heatsinks on the stepper driver chips are largely ineffective.
The STEP file for the Duet 3 Mainboard 6HC is shared on the Duet3D github here.
Caution! On v0.5 boards the GND and V_FUSED legends on the underside of the board are the wrong way round! The ones in the wiring diagram above are correct. This is the same for the jumper block OUT7 - OUT9 that provides power to these connectors respectively (see below).
Caution! On v0.5 boards, do not connect anything to the OUT pin of the IO_5 connector, because on the prototype boards this pin is used to signal to the Raspberry Pi. The IO_5_OUT pin will be available on later version boards.
|CAUTION!||The pinout of the 5-pin connectors is not the same as on the 5-pin Z-probe connector on the Duet Maestro! It has been changed to reduce the risk of shorting +5V to +3.3V.|
|CAUTION!||On v0.5 boards the GND and V_FUSED legends on the underside of the board are the wrong way round! The ones in the wiring diagram above are correct. This is the same for the jumper block OUT7 - OUT9 that provides power to these connectors respectively (see below).|
|CAUTION!||On v0.5 prototype boards, do not connect anything to the OUT pin of the IO_5 connector, because on these boards this pin is used to signal to the Raspberry Pi. The IO_5_OUT pin is available on v0.6 and later boards.|
Duet 3 Mainboard 6HC provides the following connectors:
|1 x 6-way barrier strip||POWER IN, GND, VIN||Two pins for main VIN and GND. VIN min/max: 11V to 32V|
|OUT 0 POWER IN, GND, V_OUT0||Two pins for the VIN and GND supply for the OUT_0 terminals. OUT0 voltage min/max: 0V to 32V|
|OUT 0, V_OUT0, OUT0-||Positive and negative OUT_0 terminals. OUT_0 is intended to drive a bed heater. The ground side of OUT_0 is switched by the mosfet and the positive side is protected by a 15A fuse. If using the OUT0 terminal to drive a SSR, take note that their polarity is opposite to the polarity of the VIN terminals. There is no flyback diode on this output, so if you connect a high-current inductive load, you must use an external flyback diode.|
|1 x 3-pin KK connector||EXT 5V||Open drain mosfet output for controlling an ATX-style power supply or a SSR. The +5V pin can also be used to provide external 5V power. A small amount of 5V power can be drawn from this pin (through an internal 220 ohm resistor), so that the control terminals of an SSR can be connected directly between the +5V and PS_ON pins.|
|Note: on the v0.5 board this connector is rotated 180 degrees compared to the intended orientation on later version boards.|
|6 x 4-pin JST VH connector||DRIVER_0, DRIVER_1, DRIVER_2, DRIVER_3, DRIVER_4, DRIVER_5||Stepper motor connections. (see note on JST VH connectors)|
|3 x 2-pin JST VH connector||OUT 1, OUT 2, OUT 3||These are intended for extruder heaters or fans. Maximum recommended current 6A each. These outputs are protected by flyback diodes.|
|3 x 4-pin KK connectors with offset spigot||OUT 4, OUT 5, OUT 6||These medium current outputs are intended for PWM-controllable fans. The connector fits a standard PC-type 4-pin PWM fan. Alternatively, a 2-pin fan may be connected between the V_OUT_LC_1 pin (+ve) and the OUT_n_NEG pin (-ve).|
|Note: These outputs are protected by a flyback diode connected to V_OUT_LC_1. Do not mix loads connected to V_OUT_LC_1 with the jumper set to 12V and loads connected to V_FUSED on the same bank.|
|1 x 3-pin KK header||OUT4-OUT6_SelectV||The positive supply to the OUT 4, OUT 5 and OUT 6 connectors is the centre pin of the 3-pin jumper block labeled OUT4-OUT6_SelectV. A jumper in the top position will power them from the fused VIN supply. Alternatively you can connect a 3-terminal buck regulator to the 3-pin jumper block to supply the required voltage to the centre pin.|
|3 x 2-pin KK connectors||OUT 7, OUT 8, OUT 9||These are intended for fans. Maximum recommended current 2.5A each when supplied by VIN.|
|Note: These outputs are protected by a flyback diode connected to V_OUT_LC_2. Do not mix loads connected to V_OUT_LC_2 with the jumper set to 12V and loads connected to V_FUSED on the same bank.|
|1 x 3-pin KK header||OUT7-OUT9_SelectV||The positive supply to the OUT 7, OUT 8 and OUT 9 connectors is the centre pin of the 3-pin jumper block labeled OUT7-OUT9_SelectV. A jumper in the top position will power them from the fused VIN supply. Alternatively you can connect a 3-terminal buck regulator to the 3-pin jumper block to supply the required voltage to the centre pin.|
|1 x 3-pin KK connector||SERVO, OUT 10||v0.5 boards only. This provides a 5V servo-compatible control signal and 5V power.|
|1 x 2-pin KK connector||VFUSED||This is for powering an always-on fan or similar.|
|Caution! On v0.5 boards the GND and V_FUSED legends on the underside of the board are the wrong way round! The ones on the top are correct.|
|Note: on the v0.5 board this connector is rotated 180 degrees compared to the intended orientation on later version boards.|
|1 x 2-pin KK connector||RESET_EXT||For an external normally-open reset switch.|
|1 x 2-pin KK connector||12V||Provides 12V power for a PWM-to-0 to 10V converter.|
|1 x 3-pin KK connector||LASER/VFD||v1.0 and later boards only. This provides 5V power and a 5V level signal for a TTL-compatible input to a laser controller, a PWM-to-0 to 10V converter (for variable-frequency drives), or a servo. The control signal for this output is shared with OUT9, so don't use OUT9 if you use this connector.|
|4 x 2-pin KK connectors||TEMP_0, TEMP_1, TEMP_2, TEMP_3||Connections for thermistor or PT1000 sensors.|
|1 x RJ45 network connector||Ethernet||100BaseT Port. non MDIX connect to an Ethernet switch, hub or MDIX enabled laptop port. If connecting to a non MDIX enabled port use a crossover cable. Orange LED on Ethernet port indicates Ethernet enabled, green LED indicates network activity|
|9 x 5-pin KK connectors||IO_0, IO_1, IO_2, IO_3, IO_4, IO_5, IO_6, IO_7, IO_8||These are for endstop switches, Z probes, filament monitors, servos, and other low-voltage I/O functions. Each connector provides both 3.3V and 5V power. The inputs will tolerate up to 30V. The outputs are 3.3V signals levels with 470R series resistors.|
|1 x 4-pin KK connector||DS_LED||This is to connect and power DotStar LED strips.|
|Caution! The total current draw of the Raspberry Pi (including any attached USB devices), DotStar LEDs and other devices powered from the 5V and 3.3V rails on the Duet must not exceed 3.0A.|
|1 x 6-pin JST ZH (ZHR-6) connector||SWD||This is for firmware debugging and also provides a backup mechanism to program expansion boards.|
|1 x 2x13 header||SBC||This is for connecting a single board computer (SBC) such as a Raspberry Pi.|
|1 x 2x5 header||TEMPDB||This is for connecting PT100 and thermocouple interface boards.|
|1 x RJ11 CAN connector||CAN_OUT||RJ11 CAN connector and permanent termination resistor, so it must be at one end of the CAN bus|
LEDs are provided to indicate the following:
|V_FUSED||Blue||Indicates presence of fused VIN power|
|12V+||Amber||Indicates presence of 12V power from on-board regulator|
|5V+||Red||Indicates presence of 5V power from on-board regulator|
|3.3V+||Green||Indicates presence of 3.3V power from on-board regulator|
|USB||Red||Indicates presence of 5V power from USB|
|OUT_0||Red||Next to the OUT 0 connector, indicates when on|
|OUT_1||Red||Next to the OUT 1 connector, indicates when on|
|OUT_2||Red||Next to the OUT 2 connector, indicates when on|
|OUT_3||Red||Next to the OUT 3 connector, indicates when on|
|DIAG||Red||Diagnostic LED. See description below|
Diagnostic LED This blinks continuously when the Duet 3 Mainboard 6HC is running normally, about half a second on and half a second off. Any expansion board also has a diagnostic LED. When the expansion board starts up this LED will blank rapidly. If the expansion board is connected to a Mainboard running compatible firmware, the LED on the expansion board will switch to blinking synchronously with the Mainboard LED once time sync has been established across the CAN bus.
For more information on pin names, see Pin names.
RepRapFirmware 3 uses pin names for user-accessible pins, rather than pin numbers, to communicate with individual pins on the PCB. In RRF 3 no user-accessible pins are defined at startup by default. Pins can be defined for use by a number of gcode commands, eg M574, M558, M950.
The Duet 3 series uses the pin name format "expansion-board-address.pin-name" to identify pins on expansion board, where expansion-board-address is the numeric CAN address of the board. A pin name that does not start with a sequence of decimal digits followed by a period, or that starts with "0." refers to a pin on the Duet 3 Mainboard 6HC.
|Function||Pin location||RRF3 Pin name||Notes|
|Outputs||OUT 0||out0, bedheat||High current output, bed heater|
|OUT 1||out1||Medium current outputs, hot ends|
|Outputs (4-pin)||OUT 4||out4||Fans, pumps. 2.5A limit per pin on VIN, 800mA limit total on internal 12V|
|Outputs (2-pin)||OUT 7||out7|
|OUT 9||out9, laser, vfd||Pin shared with VFD/Laser/Servo drive header|
|OUT 10 / SERVO||servo, out10||v0.5 boards only.|
|Temperature inputs||TEMP 0||temp0|
|Input/Outputs||IO_0||io0.in||Endstops, Z probes, filament monitors etc|
|SPI CS||TEMPDB||spi.cs0||Temperature daughterboard connector, for Thermocouple and PT100 boards, Accelerometer etc|
|Miscellaneous||EXT 5V||pson||For controlling an external PSU or SSR|
OUT_0 to OUT_9 are all PWM-capable. OUT_9 is shared with LASER/VFD. See tables above for notes on voltage selection and current limits.
There are 9 IO headers on board. Each has pins for input, output, 3.3V, 5V and Gnd. This enables support for a wide range of endstops, probes, filament monitors and future low bandwidth devices. RepRapFirmware 3 can be configured to map these ports to the appropriate functions as required.
Except as noted in the table below, an IO_x_IN pin can always be used to provide a digital input (e.g. for endstop inputs or filament monitors), and an IO_x_OUT pin can always be used to provide a digital output.
IO output pins can be used as inputs, but are only 3.3V tolerant. IO input pins can be used as outputs, but have 10K protection resistors in series with them, so you would need to bypass these to use them as outputs.
On the version 0.6 and 1.0 boards the individual IO_x connectors have the following additional capabilities:
|IO #||UART?||Analog in?||PWM out?||Notes|
|2||no||no||no||Could in principle be used for I2C if a resistor is changed|
On the Duet 3 Mainboard 6HC prototype v0.5 boards the capabilities are different:
|IO #||UART?||Analog in?||PWM out?||Notes|
|7||yes||no||no||In current firmware builds, dedicated to supporting a PanelDue, may not be used for any other purpose|
VIN in the range 12V-32V must be provided to the Duet. In addition the same, or a different voltage can be provided specifically for the very high current OUT0 circuit. This allows for a heated bed or similar to be run from an alternative power supply. If that is not required the same VIN can be supplied to the OUT0 input.
The Duet 3 Mainboard 6HC produces 12V onboard from VIN. 12V will not be produced if only 12V is provided as VIN. 12V is provided to the low current (800ma) fan voltage selection pins, and can be assigned to two banks of pins, OUT 4-6 and/or OUT 7-9.
The Duet 3 Mainboard 6HC also produces onboard 5V and 3.3V, from VIN. These voltages are divided for internal and external use, with external 3.3V and 5V going to IO and other headers.
External 5V power can be provided to the board by removing the jumper on 'Int 5V EN' and supplying 5V power to the 'EXT 5V' connector.
Previous versions of the Duet 3 Mainboard 6HC allowed for the Duet to power the SBC, or the SBC to power the Duet. More modern SBCs (e.g. RPi 4) needs too much 5V power, especially with a screen, to make it sensible to supply from the Duet. Similarly the spare 5V power budget on the SBC may not be sufficient for the Duet. In addition some SBCs require >5V on the 5V rail to not give an under voltage warning.
Due to this, the jumpers for 5V power between the Duet and SBC ('5V -> SBC' and 'SBC -> 5V*') are not populated on this board revision.
5V produced by the internal regulator can also provide power to a connected SBC (Single Board Computer, eg Raspberry Pi), via protection that normally prevents the SBC from backfeeding the Duet. There is an array of jumpers to customise the 5V power setup as required:
The default configuration has jumpers on the "Int 5V EN" (Internal 5V enable) and "5V -> SBC" pins only. This means the internal 5V is enabled and the SBC is powered by the Duet's 5V. The Duet can supply up to 3.0A to the SBC.
Alternatively, the SBC can provide 5V for the Duet using the "SBC -> 5V" jumper. Note that the Duet's in-built protection is bypassed. In this case the "5V->SBC" and the "SBC->5V*" jumpers should both be fitted, but remove the jumper from "Int 5V EN".
If you wish to power the Duet and SBC separately, fit just one jumper, to "Int 5V EN". The Duet will be powered by it's internal 5V regulator and the SBC from it's own 5V power supply.
Note: No other jumper configuration is recommended or supported.
Note: Newer SBCs (e.g. RPi 4) need too much 5V power, especially with a screen, to make it sensible to supply from the Duet. Similarily the spare 5V power budget on the SBC may not be sufficient for the Duet. In addition some SBCs require >5V on the 5V rail to not give an under voltage warning.
Powering a SBC like the Pi3 from the Duet is feasible provided any USB peripherals attached to the Pi are very low power draw or have their own separate power supply. Higher power draw SBC like the Pi4 may draw more power than the internal 5v on the Duet can supply, especially with added peripherals. In general, for best results, it is recommended to power the Duet and the SBC separately to avoid power overdraw issues.
Furthermore, it is recommended to use a sufficient power supply for the Pi4 that is capable of providing 5a. The official Raspberry Pi Power Supply is a good example of this. Additionally, the USB cable used to power the Pi must be of good quality.
Power overdraw conditions may result in poor communication between the Pi and Duet. The Pi may display a lightning bolt icon on the display (if connected) which is a good indication there is a power supply problem.
The Duet 3 Mainboard 6HC has a dedicated high speed SPI bus to a single board computer (SBC). The reference implementation is a Raspberry Pi 3B or newer. The SBC provides the user interface (via a browser based control application called Duet Web Control, or a third party application). It also provides a network interface via the local network or VPN depending on how it is configured. It runs a set of applications called DuetSoftwareFramework(DSF) that use the SPI bus to communicate with the Duet, as well as providing a webserver for DuetWebControl, and API for third party application, and a plugin interface specifically for gcode processing plugins.
The Duet 3 Mainboard 6HC can also be run in standalone mode (without the SBC) by using the on-board SD card socket and Ethernet interface, but then the advanced facilities of DSF are not available.
The Duet 3 Mainboard 6HC has 6 TMC 5160 stepper drivers on board. Until further testing including detailed thermal analysis is conducted these are limited to 4A RMS. The initial testing of the TMC5160s in this configuration, conducted on the Expansion board looks very promising. 4A per phase will allow driving stepper motors rated to up to 5A RMS (it is recommended to drive stepper motors at around 80% of rated maximum current).
RepRapFirmware configures these drivers over the SPI bus: dynamic setting of microstepping, current and many other features can be achieved through firmware. The drivers can be combined together to use multiple drivers on one axis (for example a 3 motor Z levelling system).
Endstops of a variety of types can be connected to any of the 9 IO headers and mapped to a specific axis. One or more Z probes can be connected (for example a different Z probe per tool). In addition filament monitors for extruder drives are supported. 9 headers allows for an endstop on 3 motion axis, 3 z probes and 3 filament monitors on 3 extruder axis - or any other combination.
The Duet 3 Mainboard 6HC has 10 PWM controlled outputs. These can be configured as heaters, fans or other devices that need a PWM signal (such as spindles or pumps). These are capable of different current outputs:
|OUT0||15A||Designed for a heated bed or similar fused to 15A but rated to 18A|
|OUT1-3||5A||Designed for extruder heaters or similar|
|OUT4-6||2A||Select between VIN and 12V for this bank of 3 fans. Headers compatible with 4 wire fans, including tacho feedback|
|OUT7-9||2A||Select between VIN and 12V for this bank of 3 fans. Standard 2 wire fans|
Note: maximum total output from the on-board 12V regulator is 1A. Because the stepper drivers require 12V as well, the current drawn from external devices must not exceed 800mA.
See CAN connection
The CAN-FD bus provides connectivity to compatible devices. Duet3D manufacture a range of expansion devices. The maximum number of expansion devices on the bus is to be determined, however we expect at least an additional 24 stepper channels via 8 x 3 channel expansion modules will be supported.
The CAN BUS is connected via RJ11 and at least 2 core twisted pair, although 6 core RJ11 is more common.
The Ethernet port provides the ability to directly network to the board when not using an SBC. Along with the built-in SD card this provides a reduced feature set method of controlling the Duet 3.
The Ethernet port may also provide potential to support EtherCat in the future if this is implemented.
Prototype board, no longer supported