Bluetooth LE trampoline wearable provides activity breakdown and trick recognition

The BERG AirHive activity tracker employs Nordic Semiconductor’s nRF52832 SoC to enable trampolinists of all skill levels to measure and track their activity

Nordic Semiconductor today announces that Stockholm, Sweden-based company Wrlds Creations has selected Nordic’s nRF52832 Bluetooth® 5.2/Bluetooth Low Energy (Bluetooth LE) general-purpose multiprotocol System-on-Chips (SoC) to provide the core processing power and wireless connectivity for its ‘BERG AirHive’ trampoline activity tracker.

Combining a 9-axis motion sensor and machine learning technology, BERG AirHive is an unobtrusive wearable that straps to the user’s right leg to accurately track their trampoline activity. Designed for all skill levels from beginners to professionals, the wearable measures a range of movement data—for example rotation speed—to allow the user to continuously record their progress and improve their skills. The company’s AI software has been developed using data gathered from gymnasts performing jumps under real conditions to identify 15 different acrobatic tricks.

Nordic’s SDK and the Nordic DevZone customer support were able to dramatically simplify our research, and shorten the development cycle

Joakim Liljedahl, Wrlds Creations

Machine learning technology

The machine learning (ML) algorithms enabled by the nRF52832 SoC’s Arm® Cortex® M4 processor with floating point (FP) unit also enable the device to ‘learn’ new tricks over time, and provide feedback to the user based on learned data. The SoC’s Arm processor is designed to support the FP and Digital Signal Processing (DSP) computations typical of high-end wireless applications such as the BERG AirHive, while the chip’s Bluetooth LE wireless connectivity allows this data to be relayed to the ‘BERG AirHive’ iOS and Android app on the user’s Bluetooth 4.0 (and later) smartphone. The app includes minigames, skill training, jump analytics and a ‘social flow’ function, which allows users to upload their latest tricks and create challenges for others in the community.

The Nordic SoC combines the 64MHz, 32-bit Arm processor with a 2.4GHz multiprotocol radio (supporting Bluetooth 5, ANT™, and proprietary 2.4GHz RF protocol software) featuring -96dB RX sensitivity, with 512kB Flash memory and 64kB RAM. Additionally, the nRF Connect SDK (recommended for nRF52832 software development) integrates the Zephyr RTOS, supports applications using Bluetooth LE, Bluetooth mesh and Thread, and includes examples, Bluetooth LE profiles and driver support for all peripherals. The SDK also includes a migration of Nordic’s Bluetooth SoftDevice Controller from the company’s proven SoftDevices used with the nRF52 Series. The nRF5 SDK can still be used for development with Nordic’s S132 SoftDevice, a Bluetooth 5-certifed RF software protocol stack for building advanced Bluetooth LE applications.

Employing a rechargeable 100mAh battery, the BERG AirHive can achieve playtime of least one week between charges (assuming usage of up to two hours a day). This is made possible thanks in part to the ultra-low power characteristics of the Nordic SoC. The nRF52832 has been engineered to minimize power consumption through features such as the 2.4GHz radio’s 5.4mA peak RX/TX currents and a fully-automatic power management system. This extended battery life was one of the key considerations when selecting the nRF52832 SoC.

Processor performance

“Strong processor performance and low power consumption was a key requirement for this application,” says Joakim Liljedahl, Co-founder and Chief Revenue Officer, Wrlds Creations. “With the nRF52832, we were able to achieve the best of both worlds.

“It wasn’t only the SoC’s hardware that appealed. Nordic’s SDK [Software Development Kit] and the Nordic DevZone customer support were also key because they were able to dramatically simplify our research, and shorten the development cycle.”