Tiny, lightweight, and long-lasting SlimeVR trackers for full-body tracking
These are a derivative of SlimeVR trackers, designed to be smaller, lighter, and longer lasting! Perfect for comfortable all-day body tracking.
- 🔧 Custom PCB - Minimal footprint carrier board
- 🏠 Custom 3D printed case - Flexible two-piece design
- 💾 Custom firmware - Optimized derivative of SlimeVR firmware
- 🔋 Extended battery life - Efficient power management
- 📡 Wireless connectivity - nRF52840-based communication
The PCB is designed in KiCad and the files can be found in the pcb folder. The PCB is designed to be as small as possible, acting as a carrier board for a Seeed Studio XIAO nRF52840 on the opposite side of the sensors.
| Component | Model | Function |
|---|---|---|
| IMU | ICM-45686 | 6-axis motion sensing |
| Magnetometer | QMC-6309 | Magnetic field detection |
High-performance 6-axis motion sensor providing accurate accelerometer and gyroscope data.
Precision 3-axis magnetic sensor for improved orientation tracking.
The board requires a LiPo battery. Size based on your needs, but the included case is designed to fit a 150mAh battery for optimal balance between size and runtime.
The case features an innovative two-piece design with a flexible interlink. The battery compartment and PCB housing are separate, connected by a flexible joint that allows the tracker to bend naturally around your body.
- Flexible interlink - Allows bending around body contours
- Strain relief - Protects battery cable from damage
- Modular design - Separate battery and PCB compartments
| Component | Recommended Material | Reason |
|---|---|---|
| Flexi-link | TPU | Flexibility and durability |
| Base plates | PETG | Strength under strain |
| Top cover | PLA or PETG | Aesthetic preference |
| Switch | PLA or PETG | Aesthetic preference |
⚠️ Important: The strap piece is under significant strain - avoid PLA for base plates as it may break!
The firmware is included as a git submodule in the firmware folder. It's a fork of the SlimeVR firmware with specific support for the Smol Biscuits PCB.
📦 Quick Start: Use the pre-compiled firmware files from the releases section to program your trackers and receiver.
Want to customize or build from source? Follow these steps:
-
Clone with submodules:
git clone --recurse-submodules https://github.com/biscuitvixen/smol-biscuits.git
-
Follow SlimeVR dev documentation: 📖 SlimeVR Compilation Guide
-
Build with correct board target:
west build -p auto -b xiao_ble -d build . -- -DNCS_TOOLCHAIN_VERSION=NONE -DBOARD_ROOT=.
⚠️ Safety First: Use proper ventilation and ESD protection when soldering
-
Solder sensor components 📊
- Solder the sensor components onto the PCB
⚠️ Leave the XIAO nRF52840 for later
-
Prepare battery terminals 🔋
- Pre-tin the battery terminals on the XIAO
- Pre-tin the corresponding footprint on the PCB
-
Position the XIAO 📱
- Use the solder jig to place the XIAO nRF52840
- Battery terminals facing up ⬆️
-
Apply flux and align ✨
- Apply flux to all connections
- Place sensor PCB on top, aligning battery terminals
-
Heat and bond 🔥
- Use square heat pass-through pads to melt solder
- Apply gentle pressure to flatten boards together
- Allow to cool completely ❄️
-
Inspect and test 🔍
- Visual inspection of all joints
- Use multimeter to check for shorts ⚡
-
Complete connections 🔗
- Solder all castellated pins around PCB edge
- Solder battery to back of sensor board
- Connect 🔌 - USB-C cable to computer
- Bootloader mode 🔄 - Double-tap reset button
- Flash bootloader 📥 - Copy
update-slimenrf_xiao_sense_bootloader-0.9.2-SlimeVR.7_nosd.uf2 - Verify ✅ - Should show as
SLIMENRF_XIAO_SENSEdrive - Flash firmware 🎯 - Copy
firmware_tracker.uf2to drive - Reboot 🔄 - Device will restart with new firmware
For Holyiot receiver:
- Use Nordic nRF Connect Programmer
- Flash
firmware_receiver.hexfile - Follow SlimeVR receiver documentation for other receivers
-
Strap preparation 📏
- Slide bases onto 30mm strap
- Ensure notches face each other 🔄
-
Flex link installation 🔗
- Place flex link between bases in designated slot
-
Battery compartment 🔋
- Insert battery spacer between strap and battery
- Position battery on top of spacer
-
Secure battery 🔒
- Hold battery in place by wires
- Snap battery base into place
-
PCB installation 📱
- Place PCB into PCB base
- Align switch with cutout ⚙️
-
Switch mechanism 🎛️
- Slide switch slider over PCB switch
-
Final assembly ✅
- Ensure case slides correctly over switch
- Snap top cover into place
-
Strap adjustment 📐
- Adjust strap to fit comfortably
- Secure in place
For complete setup and calibration instructions, refer to the official SlimeVR documentation:
🔗 SlimeVR Pairing & Calibration Guide
Your Smol Biscuits SlimeVR trackers are ready to use!
Enjoy your new lightweight, comfortable full-body tracking experience! �✨
PCB files, 3D models, schematics, and case designs are licensed under:
- CC BY-NC-SA 4.0 - Full License Text
Personal and educational use: ✅ Free to use, modify, and share
Commercial use: ❌ Requires separate license - contact [onlybiscuit7@gmail.com]
Firmware retains the original SlimeVR license terms:
- Original SlimeVR licenses: MIT | Apache 2.0
- See firmware submodule for complete licensing information
- Hobbyists & Makers: Build away! Just credit me and share improvements
- Companies: Want to sell these? Let's talk revenue sharing or licensing
- Everyone: Improvements must be shared under the same terms
- SlimeVR Firmware: Check firmware submodule for licensing terms
- Dependencies: Various open source licenses (see individual components)
I welcome contributions! Please feel free to submit pull requests or open issues.
For support and questions:
- 📖 Check the SlimeVR Documentation
- 💬 Join the SlimeVR Discord community
- 🐛 Report issues on GitHub
