⚙️ Introducing Interface C — A Modern Motor Speed Controller for LEGO® Power Functions ⚙️

[Ichoochooseyou]

Are there plans to add more countries to ship to? Probably just do the PCB kit and source everything else locally, as I presume that'll be cheaper. In the UK btw. Thanks

[diegobaca]

50 minutes ago, Ichoochooseyou said:

Are there plans to add more countries to ship to? Probably just do the PCB kit and source everything else locally, as I presume that'll be cheaper. In the UK btw. Thanks

Yes! You just need to submit the request on Tindie — I think I just saw yours come through. I’ve been adding more locations, so you should be all set.

8 hours ago, Zerobricks said:

Such a clean design and I really like how the colors match the Power Functions theme. Well done! 

Thank you! 🙏🏼 

[BatteryPoweredBricks]

The full interview with @diegobaca I mentioned in the last video is now live!  We talked a lot about the development and plans for the Interface C as well as other projects.  It was a great time, hope you all enjoy!

 

[BatteryPoweredBricks]

This is my tutorial for building the Interface C from start to finish.  There were definitely a few things that confused me at first but I eventually figured them out.  Hopefully this helps others learn from my mistakes! 
 

 

[diegobaca]

Interface C Updates:

Firmware 1.0.2 and Utility 1.0.1

I’ve released Interface C Firmware 1.0.2 along with Interface C Utility 1.0.1.

To update your device, I recommend downloading (links for PC and Mac at the bottom of the page) the latest Interface C Utility and using the Update button. You can also flash your Interface C to version 1.0.2 if you prefer. Either approach works.

What’s new in Firmware 1.0.2

This release includes performance improvements, bug fixes, and two small new features:

A) Motor Status Broadcast

One request I received was the ability for Interface C to broadcast when the motor state changes. When Motor Status is enabled in the Utility, Interface C will now broadcast messages like:

M1 set to n

Where n represents the motor speed and direction (for example, +6 or -3).

B) Serial Motor Control Command

I’ve added a new serial command that allows direct control of motor speed and direction:

Set M1 n

Where n can be any value from -6 to +6.

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New LEGO-Compatible Dial

I’ve also added a new dial design for Interface C. A few people asked for a version that supports LEGO studs, so this new dial accepts a Round 4×4 Plate with Hole, allowing you to build directly on top of the dial.

The dial can be 3D printed and is available on MakerWorld.

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What I’m Working on Next

Interface C Mini

Many of you asked for a simpler and more affordable version of Interface C. I’ve been working on Interface C mini, which includes all the core functionality of the original device but in a much smaller form factor.

My goal is to keep the total cost of parts (including the microcontroller) around $20, significantly lowering the barrier to entry. More details soon.

Firmware 1.0.3

I’m also actively working on the next major firmware update. Firmware 1.0.3 will introduce several new features, including support for custom loops that Interface C can execute on its own. I’ll share more details in the coming months.

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Thank You

Thank you to everyone who has supported the project and to everyone who has purchased an Interface C. I’m excited to keep improving the device and making it more affordable and accessible over time.

I especially want to thank Brian from @BatteryPoweredBricks for the amazing YouTube videos you created about Interface C. They have been incredibly helpful in showing what the device can do and how people can use it with their builds. 

[ukewarrior]

Do you post the files for the code and/or the PCB as open source?

[diegobaca]

On 2/28/2026 at 4:16 PM, ukewarrior said:

Do you post the files for the code and/or the PCB as open source?

I haven’t yet, but I do have plans to make my GitHub project open and public so people can tinker with it. The only things I’ve shared so far are the .stl files (3D files for the case) and the bill of materials. More announcements and exciting things are coming in the next few months! 🚀