5. Configure the system clock

The system clock configuration is done by calling the two APIs described below:

–

HAL_RCC_OscConfig(): this API configures the internal and/or external oscillators, as well as the PLL

source and factors. The user chooses to configure one or all oscillators. They can skip the PLL

configuration if there is no need to run the system at high frequency.

–

HAL_RCC_ClockConfig(): this API configures the system clock source, the flash memory latency, the

AHB prescalers, and the APB prescalers.

Initialize the peripheral

a. Write the peripheral HAL_PPP_MspInit function. Proceed as follows:

i. Enable the peripheral clock.

ii. Configure the peripheral GPIOs.

iii. Configure the DMA channel and enable DMA interrupt (if needed).

iv. Enable peripheral interrupt (if needed).

b. Edit stm32xxx_it.c to call the required interrupt handlers (peripheral and DMA), if needed.

c. Write the process complete callback functions if peripheral interrupt or DMA is going to be used.

d. In main.c, initialize the peripheral handle structure, then call the HAL_PPP_Init() function to initialize

the peripheral.

6. Develop an application

At this stage, the system is ready and the user application code development can start.

a. The HAL provides intuitive and ready-to-use APIs to configure the peripheral. It supports polling, interrupts,

and a DMA programming model, to accommodate any application requirements. For more details on how

to use each peripheral, refer to the rich example set provided in the STM32CubeU5 MCU package.

Caution:

In the default HAL implementation, a SysTick timer is used as timebase; it generates interrupts at regular time

intervals. If HAL_Delay() is called from the peripheral ISR process, make sure that the SysTick interrupt has a

higher priority (numerically lower) than the peripheral interrupt. Otherwise, the caller ISR process is blocked.

Functions affecting timebase configurations are declared as __weak to make an override possible in case of

other implementations in the user file (using a general purpose timer or other time source). For more details,

refer to the HAL_TimeBase example.

UM2883

Getting started with STM32CubeU5

UM2883 - Rev 4

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