Tutorial: Mellow Fly Pi Klipper Install

The Mellow Fly Pi is one of many single board computers (SBC) that have sprouted up over in recent time due to Raspberry Pi shortages. Mellow was one of the first 3d printer control board manufacturers to spot this trend and launched the Fly Gemini. This combined the SBC and printer controller (MCU) onto one board (check out my posts on the V2 version!). These proved to be popular and they looked to expand on this market by releasing the SBC side of the board as a standalone product. Enter the Fly Pi!

The Fly Pi offers performance somewhere around that of the Raspberry Pi 3B. Because people are struggling to get hold of Raspberry Pi’s I’ve seen a big demand in alternative cheap SBC sources so I expect this to be a popular offering.


The Fly Pi has clearly been designed as a direct competitor to the Raspberry Pi 3B the RRP is slightly at around £34 + taxes. That said that is much less than the currently inflated prices I’ve seen for official Raspberry Pi’s. The one annoyance with this board is that it doesn’t have onboard WiFi so you do have to add an external USB WiFi dongle.



The Fly Pi comes in a small cardboard box with no branding on it. It is shipped with a collection of pre-wired connectors for the accessory ports as well as JST terminals for the connectors which use those (As always this is excellent work by Mellow as it means you have connectors for everything without having to shop around). The board was in a sealed generic plastic bag which is a little disappointing as I would of expected an antistatic sealed bag like with most circuit boards. The version Mellow sent me includes the SD card and a WiFi dongle.

First impressions are that the board feels weighty! It measures in at 7.5cm*7cm*2cm. Soldering quality looks good on both top and bottom layers, as does the silk screen. There is an external WiFi antenna which will hopefully mean a good WiFi connection!

There is a wide host of connectivity available with ethernet and 4 USB type A connectors. It’s great to see an SPI header for the Accel built in as well as one for the TFT screen. There is also CAN support as well as a controllable fan port which is handy for setting up an electronics cooling fan!

A neat addition is that the 40pin GPIO expansion matches that for a raspberry pi so some accessories using that will be compatible. Note one obvious omission that there the 3V rail is not connected.

SBC OS install

The SD card provided by Mellow came with the SBC image installed already. You can check by seeing if you got an empty SD card or one with 2 segments a boot segment and a file segment. If it doesn’t you can download the image here and use raspberry pi imager to burn it onto the SD card. If it did then skip this step and jump to powering up the Fly Pi.

If you are successful when you plug the sd card into the SBC SD card slot (I’m not too keen on how little support the micro sd card has here!), the USB dongle into one of the USB A ports and connect it to your PC via the USB C port you will notice that a COM serial device appears (much like an Arduino if you are familiar with those). Install Putty by following the instructions on their website.

Open device browser to check which COM port the Gemini board has appeared as. For me the USB serial device appeared as COM6.

Open PuTTY and configure the connection as per below. You can add a name to the saved sessions box and save it for future use!

Press open and a command line interface should appear. If nothing seems to be happening you may need to hit the reset button just next to the USB C connector. You should then be greeted with a screen similar to the one below.

Now set up the WiFi connection by entering the command below


Navigate to activate a connection

Navigate to the network you are interested in and press enter (If the WiFi options haven’t appeared try running ‘sudo reboot’ and/or a power cycle as the WiFi dongle may not get detected on first boot)

Enter the password then press ok. If successful the network will appear with a * next to it indicating you are connected.

Exit out of the program back to the command line. Enter the following command to get information about the network. Look for the WLAN section and then the IP address next to the ‘inet’ line. Copy this IP address into your browser (remember its Ctrl + Shift + C to copy when in terminal)


At this point you should have the SBC side of the installation up and running and should be able to see the Fluidd interface at the ip identified in the last step.

At this point if you plan on using Fluidd you are ready to flash your controller board MCU firmware and then configure your printer. If you want to swap things over to mainsail keep on reading.

Swapping to Mainsail

This step is not mandatory but as a lot of people prefer Mainsail right now I figured I would include the steps to get you there! Run the following commands while logged in as user root.

su root //only if not already user root
nano /boot/FLY-Config.conf

This will open the text editor nano. Scroll down until the Fluidd / mainsail section and delete Fluidd and replace with mainsail as shown below. Hit ctrl + x, the y to save changes

Reboot your device.

sudo reboot

Check that you can view the mainsail web interface by going to your IP address followed by the port number you entered. for example: “

There you go. You are now running Mainsail and are ready to flash your printer controller board MCU and start configuring your printer!

Support 3DP and ME! Help us keep producing tutorials, content and mods!


3 thoughts on “Tutorial: Mellow Fly Pi Klipper Install

  1. Have you by chance saw the pinout for the host gpio pins? Trying to add more neopixels but can’t get it to work on the gpio pins yet


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: