Setting MSI,HSI or HSE and configure clock speed of SYSCLK ,HCLK and other cloks.

[MOB1]

Hello, I have a stm32wb55 nucleo board,

I want to know that whats is the logic behind that , In reference manual it says 

After a system reset, the MSI oscillator, at 4 MHz, is selected .

Lets say I want to use HSI or HSE for specific application and I want to set SYSCLK, HCLKs and other clocks .

How can I implement a code that configure HSI,HSE selection and SYSCLK etc.

I want to do that using LL(low layer libraries).

Thanks for your helps

[gbm]

Read the RefMan section on RCC module. See the description of control register and PLL configuration register.

Write the code:

• turn on the required clock source
• wait for it to stabilize
• set the PLL config and turn it on
• set the Flash wait states in FLASH->ACR
• wait for PLL to stabilize
• switch to PLL

Each item above translates to a single C statement. That's it. No HAL or LL needed. To determine the values for PLL config, you may use CubeMX clock configuration tab.

[MOB1]

When we configure project via using cube ide or MX configuration manager we can easily set clock speeds.I saw some funcitons in low layer LL libraries like LL_RCC_HSI_Enable (void ). I want to do that steps with low layer library is there some functions to set clock configs?.

[Pavel A. · Accepted solution]

In CubeMX, Project manager tab->advanced, select to use HAL or LL for RCC code.

[MOB1]

Thanks