Extending Field Deployment of Wireless Personal Use Monitors via STM32L4 Low-Power Configurations

Limited battery life in previous generations of the wireless Personal Use Monitor (wPUM) required frequent recharging during ambulatory studies and increased the risk of missing puff-topography data. The fourth-generation wPUM was designed around an STM32L433 microcontroller using low-power operating modes and an event-driven architecture. Pressure-sensor interrupts wake the microcontroller during puff activity, while periodic alarms initiate device-health monitoring. This study evaluated four STM32L4 low-power configurations—Sleep, STOP0, STOP1, and STOP2—using twenty devices, with five assigned to each mode under a standardized sensing and logging workload. Mean standby runtime was 3.27 days for Sleep, 27.78 days for STOP0, 30.15 days for STOP1, and 31.38 days for STOP2. STOP2 achieved the longest mean standby runtime with the lowest observed reliability among the STOP modes, this result was based on only two valid datasets. STOP1 had consistent operations across four valid datasets, making it the preferred configuration for extended ambulatory deployment. These findings demonstrate that low-power mode selection for embedded sensing systems must consider wake reliability in addition to power consumption.