The Keen bracelet employs a rechargeable 125 mAh battery that provides between 24 and 48 hours of continuous operation in typical use between recharge, thanks in part to the ultra low power consumption of the nRF52832 SoC. The nRF52832 SoC has been engineered to minimize power consumption with features such as the 2.4GHz radio’s 5.5mA peak RX/TX currents and a fully-automatic power management system that reduces power consumption by up to 80 percent compared with Nordic’s nRF51 Series SoCs. The result is a Bluetooth LE solution which offers 58 CoreMark/mA, up to twice as power efficient as competing devices.
“Battery life is extremely important for our device and, while it is desirable to increase the operational time, the nRF52832 allowed us to drastically improve battery life with very low-current sleep modes,” says John Pritchard, HabitAware Lead Hardware Engineer.
Nordic’s nRF52832 Bluetooth LE SoC, a member of Nordic’s sixth generation of ultra low power (ULP) wireless connectivity solutions, combines a 64MHz, 32-bit ARM® Cortex® M4F processor with a 2.4GHz multiprotocol radio (supporting Bluetooth 5, ANT™ and proprietary 2.4GHz RF software) featuring -96dB RX sensitivity, with 512kB Flash memory and 64kB RAM. When launched, the SoC was the world’s highest performance single-chip Bluetooth LE solution, delivering up to 60 percent more generic processing power, offering 10 times the Floating Point performance and twice the DSP performance compared to competing solutions.
The SoC is supplied with Nordic’s S132 SoftDevice, a Bluetooth 4.2 qualified RF software protocol stack for building advanced Bluetooth LE applications. The S132 SoftDevice Central, Peripheral, Broadcaster and Observer Bluetooth LE roles, supports up to twenty connections, and enables concurrent role operation.
“The all-in-one System-on-Chip, raw performance, and memory capacity of the nRF52832 SoC were important to us. We considerably reduced device size without sacrificing performance,” says Kirk Klobe, HabitAware Lead Firmware Engineer.
“The qualified S132 SoftDevice was also advantageous, allowing us to focus purely on our custom feature set, rather than the technical details of Bluetooth LE. We found the Software Development Kit code to be high quality and thorough, especially the drivers for all the peripherals. The Developer Kit board paired with the extensive example code let us get a working prototype up and running very quickly and iterate rapidly.”