Bringing more efficiency to power conscious devices

16th February 2016

Joe Bush

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The ultra-energy efficient ARM Cortex-M0+ STM32L0 microcontrollers from STMicroelectronics have gone into volume production. The boards include an extensive development ecosystem, including minimal cost boards and free software tools that help developers keep tight control of application power consumption and minimise time to market.

Well suited for energy sensitive applications including wearables, medical monitors, industrial sensors and smart living devices, the STM32L0 microcontroller (MCU) series achieves energy efficiency of 135 ULPMark-C certified and 158.7 ULPMark -C with a DC/DC converter. Moreover, ST’s proprietary process technology is highly temperature stable, ensuring the STM32L0 series has the best in class power consumption at 125°C, thereby combining outstanding efficiency and robustness.

Three new product lines include the STM32L0x1 Access Line, STM32L0x2 USB Line with crystal-less USB2.0 Full Speed, and the HMI ready STM32L0x3 USB/LCD Line. Memory densities are from 8KB to 192KB Flash, up to 20KB SRAM and up to 6KB true EEPROM. In addition, a new 14-pin package option makes these the world’s smallest STM32 MCUs, bringing 32-bit muscle to entry level embedded applications.

Key energy saving features of the new STM32L0 devices include a low power ADC that draws only 41µA at 12-bit resolution and 10Ksample/s; energy saving modes including 340nA Stop with full RAM retention and auto wake-up; a low power pulse counter (16-bit timer) that remains available in ultra-low power mode; and 3.5µs wake-up from Stop. There is also an interconnect matrix that allows data handling to continue while the CPU is idle.

Software development is supported by STM32CubeMX and the STM32CubeL0 middleware and firmware suite. The STM32CubeMX initialisation code generator and MCU configurator has easy to use wizards including a power consumption calculator that helps evaluate and fine tune the power budget. STM32CubeL0 includes a Hardware Abstraction Layer (HAL) that simplifies porting to other devices within the pin and code compatible STM32 family. In addition, STM32Snippets provides optimised code samples. In total, STM32Cube provides over 200 free code examples. All STM32Cube tools are available free of charge, as are the ST-Link debugger and the DfuSe and Flash Loader tools that simplify using and testing the ROM bootloader.

To get started, only minimal investment is required in low cost prototype boards, using the 32-pin small form factor Nucleo-32 boards for 16KB and 32KB variants or the 64-pin Nucleo-64 boards for 64KB and 192KB MCUs. A Discovery kit featuring an ePaper display and an Evaluation board with inductive sensing circuitry are also available. Each board hosts an ST-Link hardware debugger that provides access to all MCU pins, and an Arduino compatible connector that allows convenient functional expansion. ARM mbed compatibility gives developers free access to online tools at mbed.org.

Over 100 part numbers in the STM32L0 series are currently available, covering Flash densities from 8KB to 192KB, supported by free third party development tools including KEIL MDK-ARM, Ac6 System workbench and the GCC-based Atollic TrueSTUDIO Lite. Unlike other free IDEs, these tools are offered with no restrictions on features or devices supported.

Pricing for the STM32L0 series starts at $0.37 for the STM32L011 with 8KB Flash, 2Kbytes SRAM and 512bytes true EEPROM, for high volume orders.