A compact, coin-cell powered wearable built on the nRF platform — tracking sprint performance and long jump metrics in real time, synchronized to mobile via BLE. Engineering focus: ultra-low power consumption, intelligent sleep cycles, and reliable motion detection.

nRFPlatform

BLEConnectivity

μASleep Current

Real-TimeData Sync

Custom nRF Wearable PCB next to a wristwatch for scale

Custom PCB · Coin-Cell Form Factor

nRF SoCIMUBLE 5.0Zephyr RTOSMobile App

Overview

What We Built & Why It's Hard

We designed and developed a compact nRF-based wearable device capable of tracking sprint performance and long jump metrics, with real-time data synchronization to a mobile application via BLE.

Beyond tracking, the primary engineering focus was on power efficiency, sleep cycle optimization, and reliable motion detection — the core challenges in any wearable system. Getting accurate athletic data from a device that also needs to survive a full training session on a coin cell is a real constraint problem. Most off-the-shelf solutions don't solve this. We did.

Core Engineering Focus Areas

⚡
Power EfficiencyAggressive duty cycling and peripheral management to minimize current draw during inactive periods.
💤
Sleep Cycle OptimizationContext-aware sleep modes — device knows when an athlete is resting vs. in motion.
🏃
Reliable Motion DetectionAccurate event triggering for sprint starts, jump takeoffs, and landings without false positives.
📱
BLE Data SyncEfficient real-time data packets to mobile with minimal radio-on time.

Problem Statement

Why Most Wearables
Fail in the Field

Wearable devices often look good on a bench. The real test is a muddy track, a sweating athlete, and a battery that needs to last the session. Most fail before the finish line.

🔋

Poor Battery Life

Inefficient firmware that keeps peripherals active when they shouldn't be. Every unnecessary microsecond of MCU-on time is energy the device can't get back.

📡

Continuous Sensing Drain

Always-on IMU and radio operation is the fastest path to a dead device. Without intelligent duty cycling, sensing becomes the enemy of endurance.

🌀

Noisy Motion Detection

Raw accelerometer data is chaotic. Without proper filtering and threshold tuning, the firmware fires on vibration, clothing rustle, and handling — not actual athletic events.

📐

Bulky or Unstable PCB Design

Oversized layouts, poor antenna placement, and ground plane issues affect both form factor and RF performance — two things that can't be patched in firmware.

The goal was to build a practical, wearable-grade system — not just a lab prototype. Something that could survive real use, on a real athlete, across a real training session.

Our Approach

A Complete System —
Hardware, Firmware & BLE

We engineered a full-stack embedded solution using Nordic nRF architecture. Every layer — PCB, firmware, and wireless communication — was designed with the same constraint in mind: do more with less power.

Embedded Firmware

Event-driven. Not polling-driven.

Event-driven architectureNo continuous polling — the MCU responds to events, not a clock tick. CPU stays off until there's something to act on.

Motion-triggered activation via IMU interruptsThe IMU handles threshold detection in hardware. Firmware wakes only when a relevant motion event is confirmed.

Controlled BLE transmission intervalsRadio-on time is minimized by batching data and transmitting in tight, predictable windows rather than continuously.

Core Focus

Power Optimization

Every microamp accounted for.

Deep sleep during inactivitySystem drops into the lowest power state available whenever the athlete isn't in motion — no exceptions.

Wake-on-motion (interrupt-based)IMU interrupt lines drive the wakeup — no firmware polling loop burning current in the background.

Reduced CPU wake cyclesCareful task scheduling ensures the CPU runs the minimum number of cycles needed per event.

Fine-tuned BLE advertising & connection parametersAdvertising intervals, connection intervals, and slave latency all tuned to minimize radio duty cycle.

Custom PCB Design

Built for the wrist, not the bench.

Compact, wearable-friendly form factorSize and weight constraints drove every component placement decision — as visible in the PCB shown alongside a standard wristwatch.

RF layout for stable BLE performanceAntenna keep-out zones, ground plane management, and trace routing designed to maintain clean RF performance on-body.

Optimized power routingMinimal copper resistance paths and low-leakage component selection to prevent parasitic current drain.

Sensor + MCU in a tightly constrained footprintIMU, nRF SoC, and supporting passives integrated without compromising signal integrity or thermal performance.

Key Features

What the Device Actually Does

Five capabilities. Each one earned through real engineering decisions — not checkboxes.

Sprint Timing Detection

Start and stop events captured via IMU interrupt thresholds — no manual triggering required. The firmware knows when the athlete moves and when they stop.

Start / Stop Events

Long Jump Motion Analysis

Takeoff, flight, and landing phases distinguished from the raw IMU data stream. Filtered to ignore incidental movement and capture only meaningful athletic events.

Phase Detection

BLE Mobile Connectivity

Real-time data sync to a companion mobile app over BLE 5.0. Connection parameters tuned to reduce radio-on time while maintaining responsive data delivery.

BLE 5.0 · Real-Time Sync

Optimized Sleep Cycles

Deep sleep during all inactive periods with wake-on-motion interrupt recovery. Extended battery life without sacrificing responsiveness when the athlete is ready to move.

Deep Sleep · Wake-on-Motion

Reliable Event Detection

Threshold tuning and filtering logic eliminate false triggers from handling, vibration, or ambient movement. The device fires on athletic intent — nothing else.

Zero False Positives

Core Engineering Highlight

Sleep Cycle &
Power Efficiency

The defining challenge in this project was achieving usable battery life without compromising accuracy. Most wearables pick one. We built a system that refuses to compromise on either.

→

Result: A wearable device that is practical for real usage — not just short test sessions in a lab.

Device Power State Timeline

Deep SleepAggressive power-down. All non-essential peripherals off. IMU in low-power threshold detection mode.

μA range

Interrupt WakeIMU detects motion threshold breach. Fires interrupt line. MCU wakes in microseconds.

~μs

Active + BLE TXMinimal firmware execution. Data captured, processed, and transmitted in a controlled BLE window.

mA · brief

Return to SleepImmediately after transmission. No idle polling. No unnecessary CPU cycles.

μA range

💤

Aggressive deep sleep strategies

⚡

Interrupt-driven wake mechanisms

⏱

Minimal active-time firmware execution

📶

Controlled BLE communication windows

Outcome

What Was Delivered

Three results that separated this from a prototype exercise.

✓

Production-ready wearable PCB + firmware systemNot a proof of concept. A complete, deployable system with hardware and firmware designed to the same standard.

✓

Accurate performance tracking with minimal power consumptionSprint timing and long jump analysis that works across a real training session — not just a five-minute bench test.

✓

Scalable architecture for future sports-tech enhancementsSystem designed with expansion in mind — new metrics, new sports, new form factors can be layered in without a redesign.

What We Handled

Full-Stack Embedded Ownership

Every layer of this system was built in-house — no handoffs, no gaps.

🔲

Custom PCB DesignnRF-based wearable hardware, compact footprint

💾

Embedded Firmware DevelopmentEvent-driven, interrupt-based architecture

📶

BLE Communication & OptimizationParameter tuning, controlled TX windows

⚡

Power Management & Sleep Cycle EngineeringDeep sleep, wake-on-motion, duty cycle control

🏃

Sensor IntegrationMotion / IMU-based event detection and filtering

🏗

System ArchitectureDesigned for wearable constraints from the ground up

Work With Us

Building a wearable where battery life
and reliability actually matter?

Hire nRF developers who understand hardware, firmware, and power as one system — not three separate problems handed off between teams.

Hire nRF Developers →

✦ Custom PCB Design✦ Firmware Engineering✦ BLE & Power Optimization✦ End-to-End Delivery

Low-Power nRF Wearable forSprint & Long Jump Analysis