5 years, 2 months ago.

Oscillating current with peaks approx 1s (5uA->30uA) after calling wait () (in deepsleep) on mbed-os

Hi everyone,

I noticed an energy consumption issue on mbed-os after calling wait(). Previously, I worked on clean mbed (Mbed2) libraries and my device consumed about 4 ... 5uA after going to deepsleep mode. After rewriting the program on the mbed-os and using the built-in API for sleep modes for the STM32L476 microcontroller, I noticed that the current consumption after calling the wait () function fluctuates from the previous 4 ... 5uA up even to 30uA. As if the mbed-os work on a slow clock (tickless enabled) OS is checking something about every 1s because every 1s device raises the consumption of the current to around 30uA and after such a peak falls to the native 5uA. I switched the microcontroller to STM32L432 and I also tried to do the unmodified examples directly from the mbed team. The problem occurs all the time for different uC and unmodified example programs. For devices powered by small batteries is a serious problem. The question is, how can I slow down this work by OS in deep sleep (checking events or doing something else by mbed-os when fast clocks are off) at a slower rate to make these peaks with increased energy consumption occur less frequently eg. every 20s not on every about 1s? Maybe there is a chance to turn it off at all? Can someone explain the cause such temporary increases in the consumption after calling wait ()?