Nordic-powered wireless indoor alert system provides round-the-clock assistance to service users

SG Wireless

SG Wireless uses Nordic nRF52840 for Bluetooth LE connectivity for panic button operation

Hong Kong-based IoT technology solutions company, SG Wireless, has partnered with the local non-profit charitable organization Senior Citizen Home Safety Association (SCHSA), to develop the ‘Wireless Personal Emergency Link’ (WPEL). WPEL is an indoor Bluetooth® LE/LTE Cat 1 emergency alert system. Installed in the homes of service users, the system is designed to support senior citizens who live alone and individuals who are unable to care for themselves and whose caregivers may not always be available. 

Always-on connection

A revamp of the SCHSA’s wired landline solution, the WPEL provides service users with a guaranteed, always-on connection to the ‘Care-on-Call Service Call Centre’. This service call center is operated around-the-clock by the SCHSA, Hong Kong’s largest emergency assistance service provider that supports and delivers integrated care to over 400,000 accumulated senior citizens. The new wireless solution eliminates the need and cost for a fixed landline and makes it a viable option for a broader range of service users. 

The WPEL comprises three hardware elements: The ‘Panic Button’, which integrates the Nordic Bluetooth 5.3/Bluetooth LE nRF52840 SoC, and the ‘Main Unit’ and ‘Range Extender’, which integrate the nRF52840 SoC-based proprietary, pre-certified SGW1111 and SGW1110 modules respectively. All three devices use the nRF52840 SoC’s Long Range technology to improve radio sensitivity and, in turn, range.

Nordic’s nRF52840 is arguably the most well-rounded and cost-effective SoC in the Bluetooth LE class for its size
Ken Wong, SG Wireless

The Panic Button is designed to be wearable for portability around the home. It has an easy-to-click SOS button that instantly connects service users to the service call center following a one-button trigger to the Main Unit. The device provides Bluetooth 5 Long Range connectivity at up to 200 meters line-of-sight, which is ample coverage for the average Hong Kong apartment. The Panic Button is also IP65, IP66, and IP68 dust- and waterproof-rated and can be used indoors in bathrooms and kitchens.  

The Main Unit is a cellular gateway performing as a network access point that works with the multiple communication protocols of Hong Kong’s four network providers (CSL, SmarTone, China Mobile, and 3HK). Once installed, it enables calls over the network to the service call center when manually triggered by buttons or receiving Bluetooth LE signals from the Panic Button. The Main Unit supports up to eight Bluetooth LE connections with either the Panic Button or Range Extender at one-second response times.

The Range Extender is a plug-and-go device designed to extend Bluetooth LE distance to flexibly address various problems that disrupt connectivity in enclosed indoor areas, such as blind spots. The device eliminates the possibility of lost or missed signals from the Panic Button wherever and whenever it is triggered by service users in their homes. 

Directing data

The nRF52840 SoC acts as the system host on the Main Unit, enabling wireless communication with the Panic Button and Range Extender, as well as directing data to the backend server for processing. In addition, the SoC’s +8 dBm TX power provides extended coverage for the emergency alert system.

A web-based processing platform designed to handle voice message transmissions is used at the service call center. The platform is pre-programmed to work with each set of Panic Button, Main Unit, and Range Extender so that a unique connection to the service call center for each service user is immediately enabled when the service user plugs in the Main Unit to power. 

Under normal operation, the Main Unit is powered by 5V DC 2000 mA through a USB-C interface. In the event of a power outage, when help may be most needed, the Main Unit can also run on backup lithium batteries and the nRF52840’s low power feature significantly reduces power consumption. The Panic Button runs on a CR2450 lithium coin cell battery that provides up to three years of battery life before replacement is required. The Range Extender works directly with local power outlets and can be immediately deployed when connected to power.

“Nordic’s nRF52840 is arguably the most well-rounded and cost-effective SoC in the Bluetooth LE class for its size,’ says Ken Wong, CTO at SG Wireless. “The SoC’s 64 MHz M4 processor eliminates the need for additional processing chips, which has enabled us to develop the smallest Bluetooth LE module known in the market (10.2 by 14.1 by 1.9 mm with 72 pins). Subsequently, integrating the module ensures Bluetooth LE products are compact yet powerful, featuring Bluetooth 5 Long Range connectivity as well as high radio sensitivity.

“In addition, reference codes from Nordic’s comprehensive SDK [Software Development Kit] have undoubtedly shortened the product development cycle and enabled SG Wireless to do the same for its users,” says Wong.