The Ultralight N17 is a RepRapFirmware and Klipper compatible expansion board, developed in collaboration with Millennium Machines.

It uses CAN(-FD) to communicate with RepRapFirmware or Klipper (or anything else for that matter), allowing you to control a single bipolar stepper motor. It exposes one input port for an endstop (3 pin, PH 2.0) and one output port for any auxiliary device, e.g. a fan (2 pin, PH 2.0).

Tech Specs

• RP2350A MCU
• TMC2240 Motor Driver, 3A 36V Max*
• MCP2518 CAN-FD Controller (SPI) or direct Transceiver (MCP2542) connection to MCU
• Voltage selectable Endstop input and Aux output
• Select from VIN, 12V or 5V, shared across Endstop and Aux**
• Safe input range ~14V to ~32V
• 20-pin expansion header includes 4 x GPIO, TMC2240 A, B, N encoder pins and VIN, 12V, 5V and 3.3V

* *36V is the absolute max voltage the TMC2240 can tolerate. *

** Do not drive low-voltage, high-current devices like a 5V servo from the Aux port. High inrush current may brown-out the chosen voltage rail and cause instability - this is particularly important on the 5V rail as it drives the CAN circuitry. Ideally, use VIN for everything :)

Your INPUT voltage needs to be below this so there is enough headroom for back-EMF from the motor to be dissipated in the event of a sudden stop, without causing an overvoltage event. There is a 2 watt 'braking' resistor mounted on the board that is switched on during overvoltage events, and will dump power as heat until the voltage drops below 36V. Behaviour at these extremes is unpredictable so do NOT rely on it.

What's in the box?

• 1 x Mettle & Byte Ultralight N17 R1.5, fully assembled - no soldering required.
• 1 x 70mm Motor Cable XH 2.5 to PH 2.0 (crimped without connector installed)
• 1 x PH 2.0 connector, 6 pin
• 1 x PH 2.0 connector, 4 pin
• 1 x PH 2.0 connector, 3 pin
• 1 x PH 2.0 connector, 2 pin
• 1 x XH 2.5 connector, 4 pin
• 5 x Jumpers, 2.0 pitch, 2 pin
• 10 x PH 2.0 crimps

What isn't in the box?

• NEMA17 Motor
• 3D Printed Fan and PCB mount
• Physical documentation. Refer to our product page
• Anything else un-listed

What else do you need?

For each Ultralight N17, you will need:

• 1 x NEMA17 4 wire, bipolar stepper motor
• 1 x XT30 2+2 cable
• 1 x Optional 3010 Fan, matching your chosen IO voltage
• 1 x Optional 3D-printed PCB Mount
• 1 x Optional 3D-printed Open Frame Fan Mount

Pinout

Why Ultralight N17?

As part of my work on the Millennium Machines team, I needed a solution to be able to control a turret-style toolchanger while using all 4 axes available on the control board we recommend, the BTT Scylla.

To keep the footprint and wiring complexity down, I decided that a "backpack" style, CAN-FD connected driver might work well - mounting on the back of the motor to avoid taking up any more space.

None of the options on the market seemed to live up to my expectations. Mainly, these prioritised IO density and/or footprint, or features for use on 3D printer extruders, did not support RepRapFirmware, or did not use a motor driver that could talk SPI, limiting their usefulness in the role I had envisioned.

What makes it special?

There are not all that many options for "backpack style" motor drivers that also support RepRapFirmware, and this is my entry into the field.

The Ultralight N17 is designed to do a few things well, and nothing else.

• Drive a NEMA17 motor reliably, powerfully and quietly
• Expose just enough IO to run an extra axis and enable servo control or active cooling as necessary
• Be versatile, allowing configuration of 3 different IO voltages
• Be simple to wire up, flash, update and use
• Be open and customisable, with broken out debug headers, expansion connector, open-source schematics and (coming later) an open source PCB design
• Be priced reasonably, and worth it - prioritising quality over cost.

There are also some other reasons why you might consider the Ultralight N17 over another available option.

The Ultralight N17 is, as far as I am aware, currently the only NEMA17 backpack driver based on the RP2350A and using a TMC2240 driver.

Why is that important? Well...

The RP2350A is reasonably quick and has a hardware floating-point unit.

The TMC2240 can communicate at high speed over SPI, like its bigger brothers the TMC2160 and TMC5160. Unlike the TMC2160 and 5160 however, it integrates the H-Bridge so there is no need for external hardware - making it incredibly space efficient.

With the expansion connector on the bottom of the Ultralight N17, this makes it perfectly positioned to tackle closed loop control on NEMA17 motors in an integrated fashion, allowing RepRapFirmware full control over phase stepping and closed loop monitoring.

I intend to release an expansion board containing an AS5047 encoder, which, along with software work, should bring a reasonably cost-effective, DIY-style closed-loop solution to RRF that will allow you to upgrade any NEMA17 motor and make it closed loop!

To be clear: These boards are NOT currently capable of closed-loop control and there is no guarantee that this will EVER be possible, although the hardware has been designed with this in mind. If you DO buy one of these boards, it is with the understanding that this is an open-loop only system as shipped and no guarantee of closed-loop support in future exists.

What if you don't use RRF? Well you can of course use it with Klipper, as the board defaults to UART mode, or you can write your own custom firmware using the pico-sdk and do anything you want!

You can flash the board using the RP2350s USB Mass Storage system for really simple and quick development.

Why Mettle & Byte?

I have always wanted an excuse to design and build hardware, and this was it! It turns out that designing a CAN-FD motor controller was a bigger job than I anticipated, but I have learned a ton, and turned out what I think is a pretty cool little device.

Mettle & Byte is my one-man endeavour, and the Ultralight N17 is what I hope will be the start of something special.

I have self-funded the prototype runs and the first production run, and at these sorts of scales, PCB production and assembly is NOT cheap. By buying from me you are directly supporting further development not only on Mettle & Byte hardware, but also Millennium Machines software (MillenniumOS, ArborCtl etc) and support, where we aim to bring open, cost-effective CNC milling to the masses.

I am not in this to make a bunch of money - I am in this to make things that I think are cool and that other people might like, while supporting myself enough to explore new hardware and software ideas and to be good to the people who trust me with their equipment.

Support

A full manual is maintained on the Mettle & Byte Website, containing up-to-date pin-outs and configuration instructions.

As mentioned above, Mettle & Byte is just one person - me. I will provide best-effort support on the Millennium Machines Discord, and other members of the community may also be able to help out too. We run a pretty friendly ship over there!

You can also email help at mnb dot ltd if you are really stuck.

If shipping rates are not available for your country, please contact me directly via Lectronz, and I will try and set shipping up for you as soon as I can.

I will add delivery services on an ad-hoc basis as requests are made. It may take me some time to find all the suitable rates for a destination, so if you make a request and I add a shipping rate and it is too expensive, please message me and I will see what I can do.

I am happy to ship almost anywhere, but do need to look into rates for your particular destination before I can offer it on a wider basis.

If you are ordering multiple boards at once, I would strongly suggest asking for a tracked and insured service with a courier like DHL Express, and I am happy to set this up on request.