Hi Slimes! It’s been a while, but as the start of the crowdfunding campaign rapidly approaches, we want to share more of our progress, including behind-the-scenes info and other cool stuff about Butterfly Trackers.
For now, let’s briefly talk about the overall state of the project, including the current state, the history of what has been done, what has changed since the pre-launch page opened, what remains to do before we can launch our crowdfunding campaign, and what we want to do before Butterflies ship to customers next year. Let’s get to it!
Overall Progress
The TL;DR is that the work has been going amazingly well, albeit a little slower than we hoped. We are hard at work iterating on the hardware and firmware of both the trackers and the dongle, improving the server software for both Butterfly Trackers and the previous generation Big Trackers, and have started tackling accessories, the charging station, and marketing. We’re also prepping a whole slew of review sets to be sent to VR YouTubers for honest reviews and feedback.
Hardware
To start this off, we want to talk about all the improvements we have made to our hardware stack for Butterfly Trackers. While the overall design is effectively done, there is a lot of work that goes into these final optimization steps, work that’s incredibly important to getting a high quality product to market. We learnt a lot through our years making the original SlimeVR trackers, and we are putting that experience to good use through refinement of our design in preparation for mass manufacturing.
We are now up to Revision 10 of our PCB, but what have we improved?
Firstly, the overall PCB footprint is now even smaller, and smaller PCB equals smaller tracker. This also means we need to revisit accessories after each iteration, such as the docking station, in order to accommodate the newly shrinkified designs.
Secondly, as mentioned, we are preparing for production by rearranging and adding all the necessary features and parts to ensure manufacturing and testing are optimized and efficient. This meant adding new test points, moving parts to spots ideal for manufacturing, and improving the silkscreen. These might seem like small changes, but they’re a huge step towards having a board that is ready to go.
Finally, we are also experimenting with different USB interfaces. You can see in the design above, our newest revision includes USB integrated into the PCB design. We will be doing extremely thorough testing on this to ensure it is up to the demanding task of surviving the Slime gang. This will likely not be the final choice, but we will be trying everything to make sure what goes into the Butterfly trackers is the best possible option.
So what’s left to do, then? We want to make our batteries last even longer, both in use and when not. Making every last drop of power from the batteries count means fine tuning our power circuit to be as efficient as possible. Refinements are also being made to our antenna tuning. Board layout and design have a big influence on antenna performance, so proper tuning is essential for a well made tracker. We will be working in cooperation with Nordic Semiconductors (the maker of the communication chip we use) to make sure our tuning is perfect!
The other side of the communication equation is our Dongle, which is also getting the same level of polish as the trackers. We are happy with our current PCB design. Now, as with the trackers, comes the optimization, antenna tuning, and preparation for manufacturing.
Additionally, we need to do more work on the enclosure. While we have lots of design ideas, these need to wait for the antenna to near its final form. You can expect this to have our unique design aesthetic that "isn’t like all the other dongles".
So to summarize succinctly: All the hardware is almost ready, we’re just experimenting with stuff and working hard on getting it perfect.
Enclosure and Form
With newly designed PCB’s comes newly designed shells to house them. Version 9 of our PCB saw an overall reduction in size, as it reshuffled the onboard components significantly. In doing so, our new enclosure design had to adapt, and is now even smaller than before. Over multiple iterations, these changes add significant differences, for example, version 10 is 4 mm narrower than version 7. Our 3D printers are clutch here, as we are able to quickly fiddle with designs and iterate rapidly through fast prototyping.
We also have an injection moulding machine now, so once we find a design that sings, we are able to 3D print a mould and then injection mould a production facsimile. This lets us test final designs more accurately and effectively, which is especially useful for testing all the accessories we have planned. And all without committing to production moulds that cost thousands of dollars to make.
Charging Station
When we first opened the pre-launch page, we had a very simple prototype of the charging station. Since then, we’ve refined the trackers to use a standard USB-C port instead of the more elaborate blade connector, although that meant we had to go back to the drawing board for the charging station. While this set us back a little, we believe it’s a much better choice in the long term for both durability and design simplicity.
The pictures above show the newer designs of our single charging dock, multi-charging dock, and storage mount. These are still early on in the design phase, so there is still a lot of work to go before they are ready for production, but our aim is for a very functional design that stays aesthetically pleasing. We are SlimeVR after all, when have we done anything boring? As mentioned earlier, we also have plans for easily storing trackers while not in use, with our early designs are already getting a lot of use in the office. As usual, everything will be open source, and we are expecting a lot of creative community designs in the future.
Accessories
One of the fundamental design pillars we have for Butterfly trackers is comfort. While we are working on hugely improving our base straps which will be included in all sets, they are a generalised solution that may not be the perfect choice for some scenarios. We believe putting trackers on should be a personalized, enjoyable experience, so we have plans for multiple different accessories to customize how you wear your trackers if the default straps are not to your liking or do not suit your use case or situation.
Some of the many accessories we are designing and testing are:
- VR Socks with built-in velcro strips to easily attach trackers
- A detachable belt clip to snap on to your clothing
- Shoelace clips for direct shoe attachment
- Chest harness for a comfortable and stable chest platform
- Yoga Pants with integrated velcro strips
- Re-usable adhesive silicone pads for direct skin attachment
- Strap end-clips to make strapping on and off much simpler
Originally, we wanted backers to be able to pre-order accessories at the same time as they pre-order trackers. But unfortunately the progress on this has been slow, as iterating takes a while and our team is mostly engineers, not clothing experts.
We now have a dedicated part-time designer diligently creating and prototyping Butterfly accessories, so expect a lot more updates on this in the future as progress accelerates. Ultimately, however, this led to us deciding to reduce the scope of launch. As such, we will be focused on improving the included straps, and also the included strap clips which we feel greatly improve the experience. The optional accessories will have to wait… good stuff takes time. Don’t worry though, they will be available for purchase the moment they are deemed ready, and designs for everything will be freely available to download for 3D-printing at home.
Firmware
Another big focus of improvement for Butterfly trackers is the firmware of both the tracker and the dongle. Even though the firmware has been in development by the community for two years, there is still a lot we can improve.
The main area of firmware that we’re focusing on right now is the radio protocol. Butterfly Trackers use ESB protocol by Nordic Semiconductor, but the out-of-the-box implementation has a few issues in our unique use cases. By default, it’s not made for many active clients and so can suffer from packet loss and interference with other devices. We’re working to adapt it by implementing Time-Division Multiple Access (TDMA) algorithms, as well as frequency hopping across the wide range of channel options available to ESB devices. By launch we plan to have our implementation be a seamless user experience. Just plug and play.
On the topic of user experience, we have multiple other features being worked on solely to improve it. First up, better pairing. Instead of having to pair each set, our new protocol will have the ability to auto-magically pair with any unpaired trackers. Powering up an unpaired tracker will put it straight into search mode, and it will jump on to the first available dongle that is looking for trackers.
Second, the LED manager is getting an overhaul to make understanding the status of the dongle much easier. The LEDs’ colour and blink patterns will communicate exactly what is occurring.
Next up, the clickable button on the dongle and trackers will have multiple inputs for functions like powering off and on, resetting, or re-pairing trackers. We are still in discussion whether these will be ‘hold for x seconds’ or double/triple taps, but we will be sure to make it simple and easy to use.
And last, but not least, we need to finish the firmware update process for both trackers and the dongle. The process will be similar to our Big Slimes; Butterflies will be able to update over-the-air or via USB directly in the server software.
Software
SlimeVR Server software is the collective labor of love of many contributors and developers, and is continuously being improved upon. While Butterfly Slimes work fantastically with the current server, there is still a long way to go before they are ready for customers. Lots of things need to be added, such as guided explanations on pairing to a dongle, attaching straps to trackers, and many other onboarding and calibration steps.
Good news: it’s something we are already working on and will be implemented long before Butterfly Trackers ship to backers. Expect to see the fruits of our hard work in news and videos leading up to the launch. Which leads us perfectly into the next section…
Marketing & Reviews
No crowdfunding campaign can succeed unless people know about it! No crowd, no fund. Recently, we’ve been actively ramping up our online presence to promote Butterfly Trackers and it has been a lot of fun seeing people so excited! If you’re also excited, please make sure you are subscribed to our campaign to ensure you stay up to date and get notified when the campaign goes live. It also helps us a lot!
We’re also preparing review sets for a bunch of VR YouTubers so they can make independent reviews of the quality and comfort of Butterfly Trackers, as well as give us unbiased feedback on what we can improve. We will be sending some sets out in the next couple weeks, so keep an eye on YouTube!
Expected Timelines
So with all that said, I am sure you are wondering when you can expect Butterfly trackers to be available. Even with all the things we learnt from our highs and lows making and shipping over 30,000 of the original SlimeVR Trackers, our original estimate of August was a little too ambitious. We want to get this right, so we are taking our time to make sure that Butterfly Trackers get the love and attention they deserve.
With all that said, here are the current estimates we have for campaign milestones:
- Start of campaign: Early December 2025
- End of campaign: Mid January 2026
- First shipment: Mid 2026
These dates are not final. As you know, things can change, especially so in 202X… but we will try our best, and keep working day and night to craft tech that shakes the VR world!
See Ya Soon!
As usual, join our Discord server for weekly updates and other news! If you don’t have Discord or don’t want to join the server, we have started to post updates and other cool stuff to our social networks as well! Follow us on Bluesky, Reddit, and YouTube for regular updates, news, and other cool stuff! We’re also on TikTok, Mastodon, and Tumblr!