The Challenge
12 months of continuous physiological monitoring from a CR2450 coin cell, with BLE connectivity and weeks of onboard data storage.
The Solution
Built around the nRF52832 with a PCB trace antenna (saves cost and board space at the expense of tighter impedance matching and ground plane tuning). Aggressive duty cycling: IMU wakes MCU on motion events, sensor sampling adapts based on activity level, BLE advertising intervals stretch during inactive periods. 64Mbit SPI flash for data logging between sync sessions.
Results
Hit 14 months in accelerated discharge testing. The PCB antenna gets -68dBm at 3m, more than adequate for a wearable-to-phone link.