# Huvud 3D Printer toolhead board
A very small 3D printer board for use on a toolhead. It is designed to be used with Klipper firmware.

![Image of Board](Board.jpg)

Features: 
* TMC2209 driver
* STM32F042C6T6
* Two MOSFET drivers fans
* One bigger MOSFET driver for a hotend heater
* Thermistor input
* One endstop
* CAN bus

Main power is 12-24V. 24V is preferred to keep the currents low

The CAN Bus is not terminated, instead it uses 4 wires, termination should be done at the other end.

It uses an external 3.3V switch regulator. 

All done in KiCad

Possible issues:

* Is the cooling for the TMC2209 adequate? Seems to be, the board reaches about 50C under the TMC2209 when running a small stepper at 1A.

Change ideas:

Is the endstop useful? Could be used as a filament runout sensor.

---

2020-05-18:

First prototype production run is done.

![First board](FirstPic.jpg)

The board works mostly as intended. Some quick tests shows that the MCU can run klippy, stepper drivers, fan drivers and thermistors works perfectly fine.

2020-05-29:

![Test setup](TestSetup.jpg)

After a lot of software work and many hours of testing I can report that everything actually works as intended (except one resistor that should have been 1k was a 10k)

* The thermistor input gives a very low noise signal, even at high temperatures.
* Endstop works
* All mosfet outputs works with reasonable loads (2A at 24V). I do not have a dummy load for very high load testing, but a heater on the FAN connectors and a hotbed to the heater connector...
* The thermals of the TMC2209 seems ok. With no cooling fins or active cooling it reaches 60C (top and bottom) when mounted close to a hot stepper. I should test with a larger stepper (>1.5A) in a hotter environment to see when the TMC shuts down. I am considering a different fab that allows thicker copper layers for better heat spead, and better power margins.
* The CAN bus works good after some software work. It should work fine with up to 8 nodes on each bus, possibly more. I have run 4 boards on the same bus, each with one stepper, simulating a complete 3D printer.

It is possible to fit different connectors for most functions. It is designed for mostly angled JST-XH or screw terminals but it's possible to fit straight connectors or other 2.54mm for most functions. JLCPCB do not mount through holes so the boards come without connectors.
For a larger (>30) production run the boards would have to be panellized, which looks like a non-trivial task with KiCAD. If anyone has experience and wants to help ...


![Can Hat](CanHat.jpg)
As a sub project to this board I have developed a little power and CAN distribution board combined with an STM2515 CAN bus controller in the form of a Raspberry Pi Hat. It is a very simple little board but has turned out to be very valuable. With some more thought put into it I think it will be a good complement to the Huvud tool board. It has to be modified to allow it to be used separate from a Pi with a different CAN controller. It also needs some fuses, a proper isolated CAN tranciever, more flexibility for the CAN termination and connectivity. A an option to fit a voltage regulator to power the Pi from the boards power. And mosfets to power down the boards ... feature creep...