Bluetooth LE allows clocks to keep synchronized time in healthcare and educational applications

Primex, alarm clock

‘Smart-Sync’ synchronized time system employs Nordic’s nRF51822 SoC to provide bi-directional wireless communication between clocks in ‘self-healing’ Bluetooth Low Energy mesh.

Nordic Semiconductor today announces that Lake Geneva, WI-based Primex, Inc. has launched the Smart-Sync Bluetooth® Low Energy mesh-enabled synchronized time system, employing Nordic’s multiple award-winning nRF51822 System-on-Chip (SoC), and designed for use where accurate timekeeping is essential, for example in healthcare and education environments.

The system is comprised of a network of battery or DC-powered digital and analog clocks, a Bluetooth LE mesh bridge, and Primex’s ‘OneVue’ secure Cloud-based application platform. Each clock employs a Nordic nRF51822 SoC to provide bidirectional Bluetooth LE wireless communication with other clocks in the network and the bridge. The connectivity ensures each clock receives and shares time, as well as time zone, and daylight saving information with other clocks in the network, ensuring all the clocks remain fully synchronized.

Clock ‘wall time’ is adjusted independently of the number of nodes in the network and the network topology, with a single node serving as the master clock or ‘gateway’. Some clocks in the mesh network receive time directly from the gateway; others from other clocks. The master clock sends its current time information and measures the time elapsed between the instant of sending the time information to the instant the information is delivered to the recipient clock node. The recipient sets its clock per the information received and then queries the sender for the elapsed time, then correcting its local time accordingly. Once a clock receives the time adjustment information it can serve as a time source for other clocks.

Smart-Sync is a ‘self-healing’ system, so in the event one clock in the mesh ‘fails’, or the time source is unavailable due to a network change or outage, the clock can alternate between bridges and peer clocks to gather the current time and configuration data, enabling dynamic self-recovery of the network and ensuring the most efficient power management. A new bridge can be added to a system to improve the network quality, without the need for manual network configuration. When a new clock is added to the network, the bridge will automatically detect its presence, and add that clock to the network. Each clock in the network also periodically sends status information such as battery level, connectivity, and time accuracy statistics to the bridge, and then on to OneVue using an Ethernet or WLAN connection. Future development will take advantage of the Nordic SoC’s capabilities to securely transmit time information and status updates to authorized users over Bluetooth 4.0 (and later) mobile devices, such as phones and tablets.
We selected Nordic’s nRF51822 SoC because of the clarity of the Development Kit and responsiveness of Nordic to questions regarding the SoC’s functionality.
Brian Balboni, Primex

Each clock is powered by two D batteries, providing more than five years of battery life between replacement. Smart-Sync ‘sleeps’ between network sessions and employs a low power timer to periodically ‘wake up’ the nRF51822 SoC, which then builds a network mesh, allows for communication, system and time configuration, before again entering sleep mode, optimizing power consumption and network traffic. 

OneVue is a Cloud-based data aggregation and workflow solution, allowing users to access essential time data either from the Cloud, or their iOS or Android device. From the OneVue, web-based interface, the user can set up their network identity, preconfigure devices, and create alerting parameters and rules. OneVue can also monitor and synchronize multiple devices including clocks, timers, as well as temperature and indoor air quality sensors.

Nordic’s nRF51822 is a powerful and flexible multiprotocol SoC ideally suited for Bluetooth LE and 2.4GHz ultra low-power wireless applications. The nRF51822 is built around a 32-bit ARM® Cortex™ M0 CPU with 256kB/128kB flash and 32kB/16kB RAM. The embedded 2.4GHz transceiver is fully compliant with Bluetooth 4.2.

“We selected Nordic’s nRF51822 SoC because of the clarity of the Development Kit and responsiveness of Nordic to questions regarding the SoC’s functionality,” says Brian Balboni, Primex’s Chief Technology Officer. “The technical documentation of the Development Kit was clear and concise, and allowed my technology team to quickly implement the solution and focus on the design and development of our own proprietary functionality.”