Fly Gemini (V1) Voron 0.1 install

WARNING: This guide is only for the V1 version of the board. Use the post on configuring the V2 for the Voron 0 if you need to configure a V2 board. The steps here will not work on the V2.


Have you heard there is going to be a mellow collaboration with formbot on a voron 0.1 kit coming soon! In the pre-release pictures, you can see that the designated board will be the Fly Gemini. An all in one board that incorporates a single board computer (SBC) and the Microcontroller (MCU) into a single board!

In preparation I spent some time playing with the Beta release of the board and getting it ready for a Voron 0.1! Ok I spent a LOT of time. The default configuration provided by Mellow doesn’t work out of the box (hopefully this will be sorted by the time they release the product, I can forgive them for a few missing elements on a BETA release – For instructions on what needed fixing in the firmware take a read here)

Update (11/01/2022) – Discord user Snooze, who also created the origin wiring diagram in the article has provided an additional option for fan control which he thinks is the safest method and I agree. See the wiring portion and updated BOM


1 x Fly Gemini – Aliexpress

2mm pitch jst – Aliexpress or small heatshrink – Aliexpress
2.5mm pitch jst – Aliexpress


Apologies in advance – This board has other plans and It’s installation on the Voron 0.1 is temporary hence the precarious position it rests in. As you can see the board would fit nicely vertically with this choice of WiFi adapter or horizontally with a smaller adapter.

At this point you have a decision to make. The board only comes with one controllable fan header on the MCU so you can either use the 5v controllable fan header for the Core (just below the X end-stop) or opt for an always on configuration as depicted below. UPDATE: Or you can use the klipper expander board. The always on option is safer because the Core board can take longer to activate than the MCU but I’ve found it generally turns back on quick enough not to worry me if I get a temporary power outage etc.


UPDATE: The recommended method if you aren’t happy with an always on fan is to use the Klipper expander board to control the part cooling fans and then swap onboard fan to 5v (see blue jumper position on top right of the board) and use it for the hotend cooling.

Using Klipper expander board to solve controllable fan issues. Wiring diagram images curtesy of Snooze#6943

The connectors are all JST XH (2.5mm pitch) which for most people retrofitting this onto an existing printer will already be in place. I can only assume when they release the kit they will come with the correct connectors as my beta board (and every other board from Mellow has come with a connector for every socket on the board). Wiring is very straight forward because It’s not a big complicated machine.

If using the always on option shown below please be very careful and either use a 2mm jst ph connector or apply heat shrink around the pin from the original jst-xh connector or risk shorting your board. (I learnt this the hard way and now don’t have a working usb C connection! thankfully a rather small price to pay for my laziness / stupidity).

Don’t forget to add in a WiFi adapter because the board does not have built-in WiFi. Don’t use the bottom right USB as this is the one being used internally to connect the Core chip to the MCU.


Follow the steps in my previous blog post here if you haven’t already got your firmware loaded!

Fly Gemini Klipper Mainsail install

Printer Config

Download the and associated files from here:

I have taken the default voron zero profile and modified it to suit the fly gemini whilst trying to maintain as close as possible to stock configuration. It should work straight away but for safety I’ve commented out some key bits you will need to manually set.

Update the above printer.cfg with the following:

  • under extruder set sensor_type: EPCOS 100K B57560G104F
  • under heater_bed set sensor_type: NTC 100K MGB18-104F39050L32
  • extruder invert direction pin (remove !)|
  • Comment out heater_fan if you opted to plug it into the always on port

Once you have made those changes you should see a nice display with sensible temperatures (unlike this screenshot taken after some testing and a pid tune!)

Hardware tuning and offset calibration

Run Z_ENDSTOP_CALIBRATE and BED_SCREWS_ADJUST to get your offset correct and your bed level.

Run PID tune on hot end and bed. ‘PID_CALIBRATE HEATER=extruder TARGET=250’ and ‘PID_CALIBRATE HEATER=heater_bed TARGET=100’. Don’t forget to run SAVE_CONFIG after each one

First Print

Now it’s time for your first print! Here was mine, I messed up the z offset as I got distracted between initially doing it and doing my first print and forgot to SAVE_CONFIG! Regardless after the first few layers it turned into a very nice print. Quality straight out the gate is looking the same as with the Pi and SKR mini combo. Stay tuned for my final review of the board coming soon!

Join the discord to keep up to date and get involved in the upcoming projects!

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