Bluetooth LE proximity monitoring wearable automates workforce contact tracing

VOS Systems’ AlertTrace Mini

VOS Systems’ AlertTrace Mini uses Nordic’s nRF52840 SoC for contact tracing data transmission from device to gateway via Bluetooth LE

Nordic Semiconductor today announces that U.S.-based technology company, VOS Systems, has selected Nordic’s nRF52840 Bluetooth® 5.2/Bluetooth Low Energy (Bluetooth LE) advanced multiprotocol System-on-Chip (SoC) to power its ‘AlertTrace Mini’, a wearable solution designed to automate workforce contact tracing.

AlertTrace Mini enables companies and organizations to create a safer environment for essential employees, healthcare workers, military personnel, or anyone else working in proximity of others, by identifying the chain of people potentially exposed to Covid-19 (or any other illness) following a positive test. For example, the U.S. Air Force (USAF) has awarded VOS Systems a contract to produce, deploy, and maintain the AlertTrace Mini system for highly secure and accurate contact tracing and social distancing enforcement to help reduce the spread of viral infection in military settings.

The compact device can be attached to an individual’s shirt, jacket, belt, hard hat, lanyard, or ID card. AlertTrace Mini integrates an accelerometer, which triggers the Nordic nRF52840 SoC’s power-saving sleep mode when no movement is detected, while the Nordic SoC-enabled Bluetooth LE connectivity allows the system’s algorithms to determine the distance between devices worn by employees. The sensor and proprietary algorithm data processing capability for the AlertTrace Mini is powered by the nRF52840 SoC’s 64MHz, 32-bit Arm® Cortex® M4 processor with floating point unit (FPU). The processor is combined with a 2.4GHz multiprotocol radio and a generous 1MB Flash and 256kB RAM memory allocation.

The nRF52840 SoC incorporates the Arm CryptoCell™-310 cryptographic accelerator, offering best-in-class security. Encrypted proximity data—as well as additional safety data, time-keeping data, and further operational analytics—is securely relayed over Bluetooth LE to an ‘AlertTrace Hub’ (also employing Nordic’s nRF52840 SoC) or other gateway such as a Bluetooth 4.0 (and later) smartphone, tablet, or laptop/PC. The nRF52840 powers the AlertTrace Hub gateway to harvest the contact lists from AlertTrace Mini devices using the Bluetooth LE link. In turn, the information is relayed via a cellular network to the ‘AlertTrace’ Cloud-based platform for analysis.

Using Nordic’s nRF52840 SoC for both the AlertTrace Mini and the AlertTrace Hub made development easy, especially when creating custom Bluetooth LE services
Glenn Zelniker, VOS Systems

In the event an employee tests positive for infection, a Cloud-based dashboard displays a list of all employees to come within proximity of the infected person during the infectious period, as well as the duration of the contact. The device also features a dashboard-configurable LED and audible alert functionality to warn people whenever the designated contact tracing threshold is violated. The solution protects individual privacy by not recording any personal information or using GPS to track worker locations. In addition to contact tracing deployments across various markets and challenging RF environments, AlertTrace Mini can also be used for applications including emergency management, asset tracking, attendance automation, and location awareness.

AlertTrace Mini uses a replaceable CR2032 coin cell battery to provide battery life of between 4-6 months depending on usage and environment. The cellular-enabled AlertTrace Hub can be powered over micro-USB or via a rechargeable Li-Po battery, and can last 2-3 days on a single charge if not connected to a power source. This endurance is thanks in part to the ultra-low power characteristics of the Nordic SoC. The nRF52840 has been engineered to minimize power consumption with a fully-automatic power management system that reduces power consumption by up to 80 percent compared with the nRF51 Series.

The nRF52840 SoC is supplied with Nordic’s S140 SoftDevice, a Bluetooth 5.2-certified software protocol stack for building long range and high data throughput Bluetooth LE applications. Nordic’s unique software architecture includes a clear separation between the RF protocol software and the developer’s application code, simplifying development and ensuring the SoftDevice doesn’t get corrupted when developing, compiling, testing, and verifying the application code.

“Using Nordic’s nRF52840 SoC for both the AlertTrace Mini and the AlertTrace Hub made development easy, especially when creating custom Bluetooth LE services,” says Glenn Zelniker, Ph.D., Co-CTO of VOS Systems. “The inherent power efficiency and interoperability of Bluetooth LE, combined with the power saving features of the nRF52840, were key factors in our decision.

“The S140 SoftDevice and Nordic SDK [Software Development Kit] provided flexibility during application development without sacrificing potential features. We especially appreciate Nordic’s well-documented reference designs and the comprehensive information available through the Nordic DevZone community. These amazing resources were crucial in getting all the components of the system to market quickly and reliably.”