The BSP is based on a modular architecture allowing an easy porting on any hardware. It is done by just

implementing the low-level routines.

3.1.2

Hardware abstraction layer (HAL) and low-layer (LL)

The STM32CubeU5 HAL and LL are complementary and cover a wide range of applications requirements:

•

The HAL drivers offer high-level function-oriented highly portable APIs. They hide the MCU and peripheral

complexity to the end user.

The HAL drivers provide generic multi-instance feature-oriented APIs that simplify user application

implementation by providing ready to use processes. As an example, for the communication peripherals

(I2S, UART, and others), it provides APIs allowing initializing and configuring the peripheral, managing data

transfer based on polling, interrupt or DMA process, and handling communication errors that may raise

during communication. The HAL driver APIs are split in two categories:

–

Generic APIs that provide common and generic functions to all the STM32 series

–

Extension APIs that provide specific and customized functions for a specific family or a specific part

number.

•

The low-layer APIs provide low-level APIs at register level, with better optimization but less portability. They

require a deep knowledge of MCU and peripheral specifications.

The LL drivers are designed to offer a fast light-weight expert-oriented layer that is closer to the hardware

than the HAL. Contrary to the HAL, LL APIs are not provided for peripherals where optimized access is not

a key feature, or for those requiring heavy software configuration and/or complex upper-level stack.

The LL drivers feature:

–

A set of functions to initialize peripheral main features according to the parameters specified in data

structures

–

A set of functions used to fill initialization data structures with the reset values corresponding to each

field

–

Function for peripheral de-initialization (peripheral registers restored to their default values)

–

A set of inline functions for direct and atomic register access

–

Full independence from HAL and capability to be used in standalone mode (without HAL drivers)

–

Full coverage of the supported peripheral features

3.1.3

Basic peripheral usage examples

This layer encloses the examples built over the STM32 peripherals using only the HAL and BSP resources.

3.2

Level 1

This level is divided into two sublayers:

•

Middleware components

•

Examples based on the middleware components

3.2.1

Middleware components

The middleware is a set of libraries constructed around the Microsoft®Azure® RTOS middleware and other in-

house (STMTouch, OpenBL) and open source (TF-M, Mbed™ crypto). All are integrated and customized for

STM32 MCU devices. They are also enriched with corresponding application examples based on STM32

evaluation boards. Horizontal interactions between the components of this layer are simply done by calling the

feature APIs, while the vertical interaction with the low-layer drivers is done through specific callbacks and static

macros implemented in the library system call interface.

The main features of each middleware component are as follows:

•

ThreadX:

–

A real-time operating system (RTOS) that is designed for embedded systems with two functional

modes.

–

Common mode includes common RTOS functionalities. These functionalities are thread

management and synchronization, memory pool management, messaging, and event handling.

–

Module mode is an advanced usage mode. It enables loading and unloading of prelinked ThreadX

modules on-the-fly through a module manager.

UM2883

STM32CubeU5 architecture overview

UM2883 - Rev 4

page 6/30