Sunday, June 23, 2024

Wearable Sensor Unit Reference Design

The reference design fits within a watch strap for real-time activity monitoring and seamless sensor interaction, optimized for wearable and portable applications.

Wearable sensor

Wearable sensor units have emerged as transformative tools across a wide array of applications, from personal health monitoring and fitness tracking to enhancing safety in hazardous work environments and aiding military operations. These devices offer continuous, real-time data collection, allowing for the precise monitoring of physiological and environmental conditions. Their ability to provide critical insights and alerts helps manage chronic health conditions, optimize physical training, ensure worker safety, and support elderly independence. The STEVAL-WESU1 is a reference design from STMicroelectronics optimized for designers implementing advanced technologies in wearable and portable applications.

The design’s compact hardware fits within a watch strap, enabling real-time activity monitoring and immediate interaction with sensor data acquisition. The firmware, based on STM32Cube software technology, allows for easy enhancement with additional algorithms.

An application layer, based on the BlueST protocol, facilitates data streaming from various devices including inertial and environmental sensors, as well as battery devices and RSSI. A serial console over BLE allows for the adjustment of configuration parameters. Additionally, the ST-WESU™ app leverages the BlueST protocol to log all sensor data and provides demonstrations for algorithms, battery detection, and RSSI levels. It also features a command line interface through a debug console, offering extensive control via internal permanent and session setting registers

The compact solution is suited for wearable motion sensing applications and comes equipped with a comprehensive suite of firmware examples to assist developers. The system is compatible with both iOS and Android apps, making it accessible for a wide range of users. 

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Key components of this system include the STM32L151VEY6, a 32-bit ultra-low-power microcontroller, and the LSM6DS3, which combines a 3D accelerometer and 3D gyroscope for dynamic motion sensing. Additionally, it features the LIS3MDL 3-axis magnetometer, the LPS25HB MEMS pressure sensor, and the BlueNRG-MS Bluetooth Low Energy network processor. The connectivity is enhanced by a BALF-NRG-01D3, a 50 Ω balun with an integrated harmonic filter, and power management is handled by the STNS01 Li-Ion linear battery charger and the STC3115 fuel gauge IC.

A 100 mAh Li-Ion battery powers the device, which has been tested and certified according to UN38.3 standards. For ease of use, it includes a micro USB connector for recharging and an SWD connector for debugging and programming. The product package also contains a watch strap with a plastic housing for immediate wearability. In terms of regulatory compliance, the device is fully tested and certified by the FCC and IC and meets RoHS standards, ensuring its safety and environmental friendliness.

STMicroelectronics has tested this reference design. It comes with a Bill of Material (BOM), schematics, assembly drawing, Printed Circuit Board (PCB) layout, etc. You can find additional data about the reference design on the company’s website. To read more about this reference design, click here.

Nidhi Agarwal
Nidhi Agarwal
Nidhi Agarwal is a journalist at EFY. She is an Electronics and Communication Engineer with over five years of academic experience. Her expertise lies in working with development boards and IoT cloud. She enjoys writing as it enables her to share her knowledge and insights related to electronics, with like-minded techies.


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