The Duet 3 Mainboard 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 main boards, expansion boards, smart tool boards and custom expansion modules. The flexibility of configuration and advanced features are enabled by our innovative RepRapFirmware 3 running on the Mainboard and DuetSoftwareFramework running on the single board computer.

Initial documentation is available at: Duet 3 prototype guide for OEMs with full documentation under development now.

The Duet 3 Mainboard 6HC is the first version of the main board produced.

• Powerful 32 Bit Processor: Atmel ATSAME70: ARM Cortex-M7 microcontroller running at up to 300MHz, with 1Mb flash memory, 384Kb RAM and many peripherals.
• Dedicated SPI Bus to Single Board Computer (SBC): User Interface and networking handled by the SBC: this leaves the main processor free to do precise stepper pulse timing and implement other advanced features, and the USB bus on the SBC free for storage devices, webcams, scanners etc.. We are using the Raspberry Pi 3B+ and 4 as the reference platforms but support is planned for other single board computers with appropriate SPI interface.
• Six high-current advanced TMC5160 stepper drivers: SPI controlled will all the latest Trinamic features. Maximum motor current 6.3A peak per phase (4.45A RMS).
• 2x CAN-FD BUSs for expansion to multiple expansion board and bus connected tools.
• Bed heater channel designed for high current (18A¹)
• Triple extruders: 3 medium current heater channels for up to 3 extruders.
• 6 PWM controllable fan channels. 3 of these support 4 wire fans including tacho reading. These can be run from either the input voltage, from 12V, or from external power for added flexibility. Also one always-on fan connector supplied with VIN voltage.
• Fuses fitted for input power and the high current bed heater
• Connect via PC, tablet or smartphone to the Duet Web Control web interface running on the SBC. There is no need for an app install, internet connectivity or cloud service to sign up for. You can control your printer, upload and start prints from the browser.
• Setup your printer and update the firmware through the web interface. No need to compile your own firmware.
• Add a HDMI touch screen to the SBC for a easy touch based UI.
• Also connect via Ethernet, USB or serial if desired.
• Most printers supported: all common 3D printer geometries are supported (and some uncommon ones as well), with easily modified configuration templates for popular designs. Along with 3D printers, a wide variety of CNC machines and laser cutters can be controlled.
• Expandable with Duet 3 expansion boards under development. At least another 24 stepper channels are expected to be supported.
• Firmware support for tool changers, mixing nozzles and remapping axes for maximum flexibility.
• Advanced Calibration Support: Use a wide variety of Z probe types to calibrate a printer, build a mesh representation of your printer's bed and compensate for axis sag and other issues.
• Automatic ADC gain calibration for thermistors allows for accurate and repeatable temperature setting. PT1000 sensors are supported in addition to thermistors. In addition PT100 and Thermocouples are supported through SPI daughter boards.
• Power monitoring to allow for state save on power fail.
• Support for the Duet3d Filament Monitors both magnetic and laser versions.

¹ Note that the board is rated to 18A on the bed heater channel; however it is supplied with a 15A fuse fitted (18A are difficult to source). If you need 18A on the bed heater channel then you need to fit a 20A fuse and take further precautions against over-current.

For wiring , see Duet 3 Mainboard 6HC Wiring Diagram

For dimensions, see Duet 3 Mainboard Dimensions

The Duet 3 mainboard 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.

Documentation for DSF to follow

The CAN-FD bus provides connectivity to compatible devices. Duet3D will be manufacturing a range of expansion devices, starting with a 3 channel expansion board 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 - along with the built in SD card this provides a reduced feature set (similar to Duet 2) method of controlling the Duet 3.

The Ethernet port may also provide potential to support EtherCat in the future if this is implemented.

There are 9 IO headers on board. Each has an input and output along with 3.3V, 5V and Gnd supplied. This enables them to support 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.

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 produces onboard 12V, 5V and 3.3V, from VIN (12V will not be produced if only 12V is provided as VIN).

These voltages are divided for internal and external use. with external 3.3V and 5V going to IO and other headers, and external 12V if provided to the low current fan voltage selection pins.

5V produced by the internal regulator is provided to power the connected SBC, 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:

In normal operation the internal 5V is enabled and the SBC is powered by the Duet's 5V. Alternatively the protection can be bypassed and the SBC can provide 5V for the Duet using the "SBC -> 5V" jumper. In this case the 5V->SBC and the SBC->5V* jumpers are both fitted.

to follow

The Duet 3 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.

Todo: document the additional functions such as PWM/analog/UART etc available on the IO headers

The Duet 3 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). There are capable of different current outputs:

LEDs are provided to indicate the following:

Power

Blue: VIN

Amber: 12V

Red: 5V

Red: USB

Green: 3.3v

Outputs

Red: Out 0- Out3 next to the connectors

Diag

Red: Diagnosis LED