The device
A quiet instrument worn on the wrist.
ESP32-S3 at the core, five biosensors on the front, a power tree underneath, and Bluetooth Low Energy to the phone. Every component is chosen so the band can disappear under a sleeve.
Spotlight
Built for the wrist that needs to be heard.
Calmix lives where the body speaks. Heartbeat, sweat, breath — read continuously, gently, without screens that demand attention.
- Medical-grade silicone, 18 g total mass
- Always-on ECG + PPG · 250 Hz
- Adaptive haptic — three intensity profiles
- IP67 splash + sweat tested
Anatomy
Anatomy
ESP32-S3
Dual-core, BLE 5.0, low-power deep-sleep states. Handles acquisition, feature extraction and on-device scoring.
Local cache
Rolling buffer for offline sessions. Sessions sync to the phone over BLE when the user is ready.
Two-layer board
Sensors on the front, regulators on the back, ground planes separating noisy switching from analog front-ends.
USB-C
Single port for charge and serial debug. No proprietary cables.
Signal flow
From skin to insight in 80 milliseconds.
Five stages, one closed loop. Calmix samples, filters, classifies, and responds — all before you notice.
Skin
PPG · EDA · IMU
Sensors
Analog front-end
MCU
TinyML inference
BLE
Encrypted packets
Phone
Gentle nudge
Sensors
Six sensors, one calibrated picture
PPG · Heart
Optical PPG via red + IR LEDs. Returns HR and the building blocks for HRV (SDNN, RMSSD) and a derived respiration channel.
EDA · Sweat
Two skin-contact electrodes measure conductance. Tonic SCL tracks slow arousal; phasic SCRs flag acute spikes within seconds.
Skin temperature
Medical-grade ±0.1 °C accuracy. Peripheral temperature drops are a clean signature of stress-induced vasoconstriction.
Motion
3-axis accelerometer providing motion gating, activity context and step counts. Differentiates a walk from a panic attack.
Respiration
Breath rate inferred from the PPG envelope so no chest strap is needed. Useful when sympathetic load spikes the breathing pattern.
Cortisol probe
Future expansion: a discrete sweat-based cortisol micro-sensor for slower-axis (HPA) confirmation.
By the numbers
Battery life · 24/7 sampling
ECG + PPG sample rate
Total wrist mass
Skin → insight latency
Power tree
A power tree built for silence
Wearables fail when the rails are noisy. Each rail is regulated, separated and slow.
Buck-boost
Holds a stable 3.3 V across the full Li-Ion swing so sensors never see a sag during heavy radio bursts.
Charger
Single-cell Li-Ion CC/CV charger from a 5 V USB-C input with protection.
3.3 V LDO
Ultra-low-noise rail for the analog front-ends and the PPG LEDs.
1.8 V LDO
Quiet sub-rail for low-power subsystems and digital sensor logic.
Closed loop
Closed-loop architecture
Sensors → conditioning → feature extraction → stress estimator → recommendations → user feedback → adaptive update. The loop never opens.
Sense
Five modalities, one synchronized clock.
Condition
Filter, denoise, motion-gate.
Extract
HR, HRV, SCL, SCRs, temp trend, activity.
Score
Hybrid model → 0–100 score.
Recommend
Breath, alert, ERP cue.
Adapt
User feedback updates the model weights.
Industrial design
Three design directions
The same closed-loop electronics, three industrial design languages. The user picks the one that disappears into their day.
Minimal
Black silicone, brushed steel bezel, AMOLED with a quiet teal waveform. For people who prefer to forget the watch is there.
Clinical
Soft white medical band with a sensor disc underneath. For trials, hospitals and clinicians who want the device to look intentional.
Hybrid
Tan leather, ivory dial, radial bars instead of dashboards. For everyday wear without giving up data fidelity.