After evaluating different 32-bit microcontroller lines for a long time, I decided to choose STM32 from electronics giant ST Microelectronics as the new platform for future projects. To quote the product site:
The STM32 family of 32‑bit Flash microcontrollers based on the ARM Cortex™‑M processor is designed to offer new degrees of freedom to MCU users. It offers a 32‑bit product range that combines high performance, real-time capabilities, digital signal processing, and low‑power, low‑voltage operation, while maintaining full integration and ease of development.
The unparalleled and large range of STM32 devices, based on an industry-standard core and accompanied by a vast choice of tools and software, makes this family of products the ideal choice, both for small projects and for entire platform decisions.
With my keen interest for low-power design, I have worried about the sleep and shutdown power consumption of 32-bit MCUs. However, since February 2014 ST offers the STM32L0 line which can reach as low as 200 nA and under 1 µA with real-time clock enabled.
Some 8-bit MCUs like PIC XLP (Extreme low power) are still superior in low power consumption, stating lowest current level 9 nA and with RTC 400 nA. However, at these low power levels every part of the system has to be scrutinized to eliminate small currents that would quickly become a dominant factor compared to the theoretical MCU power limit. Advertised battery life up to 20 years is also very questionable due to battery aging and other factors. The hunt for lowest-power MCU is a debated area and not easily compared — wake-up time, particulars of sleep modes, active current at different clock frequencies and sources all make the picture fuzzy indeed. Either way, when looking at the projects Sparv currently has at hand a system power budget of 1~5 µA when idling goes a long way.
The wide range of STM32 microcontrollers should prove the ecosystem fit for many projects to come.