The velocity sensor with nothing to hide.
ODKI‑VBT measures bar velocity, displacement, and reps in real time — and publishes exactly how. No black box, no closed protocol.
We build training sensors,
not black boxes.
Most VBT devices ask you to trust a number you can't check. ODKI publishes the algorithm, the hardware, and the Bluetooth protocol — build your own, or buy one built by us.
Transparent by design
Every stage of the algorithm is documented, not hidden.
Yours to open
Firmware and hardware are source‑available — read it, build it.
No walled garden
BLE protocol is CC0 — any app can connect, not just ours.
ODKI‑VBT sensor
REF. DESIGN: XIAO‑NRF52840‑S
DOC: FIRMWARE/DOCUMENTATION.MD
- Core
- nRF52840 + LSM6DS3TR‑C 6‑axis IMU
- Connectivity
- BLE 5.0 / 5.4, open spec
- Sampling
- 100 Hz fusion loop, up to 416 Hz IMU
- Live stream
- 20 Hz over BLE
- Per‑rep data
- Velocity, acceleration, displacement, quality score
- Mounting
- Magnetic — seconds to attach
- Battery
- 400 mAh Li‑Po, USB‑C
- Updates
- OTA via BLE
- Openness
- GPL‑3.0 · CC BY‑NC‑SA 4.0 · CC0
From raw motion to a trusted number.
Four stages, fully documented — from accelerometer to the number on screen.
Read the motion
IMU polled up to 416 Hz, median‑filtered to reject shocks without smearing real movement.
Fix the orientation
A Madgwick filter fuses accelerometer + gyroscope into a stable 3D orientation.
Correct the drift
Velocity is never force‑reset — drift is measured, then removed retroactively.
Report the rep
Peak/mean velocity, acceleration, and a quality score — pushed live over BLE.
Why zero‑velocity resets were scrapped for retroactive correction — full writeup in the docs.
The app that talks to your sensor.
STATUS: AVAILABLE NOW
IOS / WINDOWS: ROADMAP
Live rep data on your phone, over the open BLE protocol. Android now — iOS and Windows next.
Peak & mean, every rep
Velocity and acceleration, computed automatically — no manual logging.
A session for every exercise
Sets organized by exercise, so progress is easy to follow.
Watch the trace live
The velocity curve renders live, as you lift.
Firmware, updated over the air
New firmware ships to the sensor over Bluetooth — no cables.
Find your Fmax, calculate your 1RM
A proper force–velocity test, with an estimated 1RM.
Get the ODKI app
Free to pair and track. AI analysis and data tools are paid add‑ons.
Built for anyone who needs the real number.
One sensor, one open protocol — three very different ways to use it.
Personal trainers
Auto‑regulate load from live velocity, and catch bad reps early.
- Track your client's progress, session to session
- Boost retention — show clear, objective progress, or exactly where a missed session shows up in the numbers
- Simple to use: plug and play — no complex measurement rig, just a magnetic mount on the bar
Universities & research
A sensor you can validate — open spec, raw data, reproducible results.
- Byte‑exact BLE protocol spec for custom capture pipelines
- Raw per‑sample debug log over USB serial, with an included Python viewer
- Fully documented, citable rep‑detection algorithm
Fitness enthusiasts
Track bar speed like pace or heart rate — real feedback, set to set.
- Pair once, track every session from the companion app
- Build it yourself to keep costs down, or buy it ready to go
- No subscription required to use the sensor itself
Build it. Or buy it.
Same source‑available firmware, same open protocol, either way. Pick whichever fits your time and your toolbox.
Build it yourself
Full BOM, firmware source, and build docs — source‑available, not OSI "open source" (see what that means).
- Complete BOM with sourcing notes
- Arduino firmware source + full documentation
- BLE protocol spec (CC0) for your own app
- Free for personal & non‑commercial use
Buy ODKI‑VBT
Factory‑built, calibrated, backed by ODKI — same firmware and protocol inside.
- Assembled, tested & calibrated unit
- ODKI‑branded case included
- Same open BLE protocol — no lock‑in
- Firmware OTA updates over BLE
- Support directly from ODKI
ODKI‑VBT case, on its own
Zip case with an internal magnetic mount. Included when you buy the sensor — sold separately for self‑builds.
Sensor shown inside for scale — not included with the case on its own. Every case ships with the same line lasered on the back: “Keep out of reach of excuses.”
Reserve yours.
The first assembly run is being organized now. Pre‑order to lock in launch pricing and get first access when units ship — no payment is taken at this stage.
LICENSE-HARDWARE / LICENSE-FIRMWARE in the repo. The BLE protocol alone is CC0 — fully public, no conditions.