Nordic nRF52840

Why the nRF52840 works well for wearable products

With its 64 MHz Arm Cortex-M4 processor with a floating-point unit, 1 MB of flash memory and 256 KB of RAM, Nordic Semiconductor's nRF52840 is the right choice for wearable makers who need space for their Bluetooth stack and other things that go into the device such as application logic, sensor processing, diagnostics and updates.

The radio supports Bluetooth LE and a number of 2.4 GHz protocols, with Bluetooth LE as the means of connection in many cases, supported by NFC-A making the process easier and USB being available for charging and support.

The device also provides interfaces for wearable components, including SPI, TWI, UART, PDM, I2S, QSPI, PWM, and a 12-bit ADC. Hardware cryptography and CryptoCell support help with secure communication and firmware verification.

Nordic's power-management architecture gives firmware teams fine control over sleep states, wake sources, radio activity, and peripheral use.

Our nRF52840 wearable development services

Product discovery and technical feasibility

To start with, we present definitions about the wearable being analyzed, including the number of measures, behaviors of the decisions made locally, and how users interact with the wearables.

The battery power, case shape, recharging type, Bluetooth capabilities, storage time, accuracy of the sensor, contact with skin, area surroundings, and legal requirements are all of primary importance.

We then test the riskiest assumptions. A prototype may compare optical sensors on skin positions, measure antenna performance near the body, or determine whether the proposed algorithm can run within the available memory and power budget.

Custom wearable electronics and PCB design

Our electronics specialists create small-sized nRF52840 boards by working within mechanical limits. The design may consist of an IMU, optical heart-rate or SpO2 sensor, temperature sensor, pressure sensor, haptic motor, LEDs, buttons, external flash, NFC antenna, USB, charging circuit, fuel gauge, and protective components.

We review sensor placement, grounding, flex and rigid-flex options, battery safety, charging temperature, ESD, waterproofing boundaries, programming pads, and production test access.

RF layout and antenna clearance are enclosure decisions because the wrist, battery, display, and metal fasteners change RF behavior.

Embedded firmware and sensor processing

We build firmware with the nRF Connect SDK and Zephyr for products, while supporting established nRF5 SDK codebases during maintenance or migration. Firmware work includes device drivers, sensor scheduling, Bluetooth services, local storage, event detection, user feedback, power states, diagnostics, and device firmware updates.

We precisely utilize the peripheral devices of hardware and interrupts to ensure that CPU goes to sleep after completing the work. Instead, sensor information can be processed, merged, and summarized internally within the wearable before getting transmitted, thereby cutting back the radio time and duty of the mobile device.

Bluetooth, mobile application, and cloud integration

Our product experience is based on trustful pairing. In our process, we create customized GATT services, develop advertising strategies, define connection parameters, establish bonding, set privacy protocols, provide data framing, plan retries, and ensure synchronization.

Our mobile app will help with configuring the system, showing results, saving the history, setting alerts, and securely updating the firmware.

We develop iOS and Android apps or cross-platform applications using Flutter, React Native, or .NET MAUI.

Some wearables only need a phone, others communicate with gateways in workplaces, hospitals, gyms, or care facilities.

We design the correct topology and decide what happens when neither path is available. Local queues, timestamps, deduplication, and reconnect logic prevent missing or repeated records.

When cloud services are required, our backend team builds device registration, user accounts, telemetry storage, alert rules, dashboards, fleet health, and controlled firmware-release workflows.

Battery life is an engineering result, not a datasheet promise

The battery life of a wearable device is determined by the duty cycle. Important factors include sensor warm-up time, LED current, sampling rate, flash writes, advertising intervals, number of connections, and number of retries. We develop a power budget based on the operating conditions we measured before profiling actual firmware running on a prototype board.

This often reveals that a sensor or user-interface decision consumes more energy than the microcontroller.

Optimization may involve batching samples, adapting measurement frequency, shortening radio activity, using DMA, shutting down external components, and waking only from meaningful events.

We test poor-signal conditions, because repeated connection attempts can drain a battery. The final charging and state-of-charge experience is validated across temperatures and user behavior rather than estimated from nominal battery capacity.

Security, testing, and production readiness

Personal data, passwords, or safety details may be stored in wearable devices. We utilize secure association methods, encrypted communication, firmware signatures, key protection mechanisms, the secure updates, and monitored factory setup.

There are many decisions that need to be made about how to handle a device when it gets debug access, when it is reset, when it is transferred to a new owner, when it is lost, and when an account is deleted.

The testing phase includes functionalities of firmware. Issues related to the disconnection, power shortage, and issues stemming from the unavailability of storage are eliminated during testing. The hardware sample typically goes through RF testing, charging testing, thermal testing, ESD testing, and environmental testing as per the specifications of the product.

Prior to manufacturing, test firmware is created and all the necessary procedures of programming, calibration, serial number management, acceptance criteria, and releasing packages are established.

Case Study: nRF52840 connected-worker safety wristband

nRF52840 connected-worker safety wristband

The requirement of the product

In order to maintain confidentiality, the customer and sites are not named. The maintenance crews worked in huge warehouses and remote utility locations where phones were mostly kept either in tooldes and pockets.

The customer was after a lightweight wristband capable of identifying if a person would fall, be inactive for a certain time, have an SOS button, and tell if the person was in a restricted area.

Hardware and firmware design

The nRF52840 was identified as the ideal model for Bluetooth Low Energy, memory capacity, near field communication functionality, encryption, and energy-efficient operation. The circuit contains a six-axis IMU, vibration motor, buzzer, LED to indicate the status, side-button, external memory storage, battery charger, and fuel gauging circuit among others in the entire build.

Using an NFC tag, a wristband could be assigned to an operator when switching shifts. Testing of the antenna was conducted with the complete enclosure and, in addition, on wrist sizes, not only on the PCB resting on the desk.

The firmware measured movement at various frequencies based on the activity being performed. In a low-energy state, the device waited for movements and only began more intensive monitoring after a sudden acceleration.

The logic of falling included the force of impact, the direction of motion, and the movements after it.

One threshold alone did not trigger an alarm. When a possible fall was detected, the band vibrated first and allowed the wearer to cancel the alert.

A confirmed event stored a timestamped motion summary and attempted delivery through the nearest gateway or paired phone.

Mobile, gateway, and field behavior

BLE advertisements carried a status record, while authenticated connections handled configuration, event transfer, and firmware updates. Gateways forwarded alerts to a cloud service, where supervisors saw worker assignment, event type, battery state, and last contact.

The mobile app supported commissioning, alert acknowledgement, device checks, and secure updates. Without a gateway or phone, events remained in flash and synchronized later without duplication.

The field tests uncovered problems that were not obvious during the tests. In some cases, the repetitive use of the tool produced some impact effects; in others, the use of winter clothing limited the sound output, allowing the workers to touch the antenna.

We made changes in the timing protocols, haptic signals, antenna tuning, and added an automated fit check. The energy data indicated that repeated reconnections under poor reception required more energy than motion processing.

The firmware therefore reduced unnecessary reconnect attempts and used advertising for routine status.

The completed wristband provided consistent safety reporting without turning it into a surveillance device.

Local processing kept raw motion on the band unless an event required evidence. The nRF52840 gave us memory and processing capacity for sensing, event logic, secure updates, and diagnostics while maintaining the low-power behavior expected from a shift-length wearable.

Our Nordic Wearable Experience Is Not Limited to a Single Project

The case study above represents only one example of our work with Nordic Semiconductor technology. We have completed multiple wearable projects using nRF52832, nRF52840, nRF52-series, and nRF54H20 platforms.

Our experience covers healthcare wearables, fitness devices, smart rings, safety products, rehabilitation systems, medical compliance, native mobile applications, and privacy-focused AI wearables. Selected projects from our website are presented below.

From engineering sample to production wearable

The development process can be divided into various stages, which include the feasibility study of sensors and radio, the electronics, development of firmware, prototyping the enclosure, mobile integration and cloud integration, tests in the fiend, preparing for certification, and production.

Every stage has its own acceptance criteria, and this gives the possibility for the developers to improve the placement of the antenna, the functioning of the sensors, charging, and user interaction before it is too late and the changes will be costly due to tooling and certifications.

Support for production may involve numerous activities from substituting materials to factory testing, managing firmware releases, troubleshooting, maintaining mobile applications, and cloud monitoring.

Continuity of these processes is of utmost importance because the performance of the wearable device hinges upon the interactions among the body, case, electronic components, radio signal, firmware, and services.

Products which we make by using nRF52840

The devices that we produce include activity trackers, safety wearables, rehabilitation devices, smart badges, medical appliances, sports gadgets, posture control devices, location tracking tags, haptic devices and remote controllers.

We are also able to upgrade a wearable device, facilitate battery operation, correct the defect in the BLE, and transfer a product based on nRF5 SDK to the technology of nRF Connect SDK.

Start your nRF52840 wearable project

The process of IoT App Development involves combining various elements such as wearables technology, Nordic firmware, Bluetooth technology, cloud technology as well as testing and manufacturing engineers into a single cohesive group of experts.

We can work closely with you to gather the required parameters such as user needs, measurements, battery goals, maximum size of the enclosures, and deployment methods.

Then, we will transform this information into an efficient architecture and development plan which is rather useful and practical rather than just demonstrational with specification of endurance and fabrication milestones.