STMicroelectronics has completed importing its free low-layer application programming interface (LL API) software into the STM32Cube software package that supports all STM32 microcontrollers (MCUs). LL API software enables professional developers to develop applications in the easy-to-use STMCube ™ environment, using ST-verified software to optimize code down to the register level, thereby reducing time to market.

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 Integrate LL API and hardware abstraction layer (HAL) software in all STM32Cube packages, giving developers full freedom to choose peripheral control methods. They can choose to take advantage of the ease of use and portability of HAL, or use LL API software to optimize performance, code size, and power consumption. Provides a template for the custom routines of the related STM32 Nucleo development board, which helps to simplify the porting of code between STM32 MCUs.

Because it has software features equivalent to the peripheral initialization service of the STM32 Standard Peripheral Library (SPL), the LL API provides a shortcut for upgrading the development environment from the past SPL to a simple but powerful STM32Cube ecosystem. Using the LL API can achieve excellent performance, comparable to the performance of the STM32 direct register access routine code segment.

Unless otherwise noted, the LL APIs conform to the MISRA-C 2004 standard, and use the Grammatech CodeSonar® analysis method to verify whether the code quality and reliability are optimized. STM32CubeMX's automatic update function ensures that the user's LL API software is always the latest version.

As a tool to further improve production efficiency, the STM32CubeMX tool uses LL API software to automatically generate peripheral initialization codes. Currently it supports four series: STM32L0, STM32F0, STM32L4 and STM32F3. The support range will be expanded to the remaining STM32 series products in the next few months. STMicroelectronics also provides SPL to LL code migration guide documentation and automation tools.