STM32 novice initialization function and delay function

1. STM32 clock configuration initialization function:

void Stm32_Clock_Init(){

unsigned char temp = 0; //define an unsigned char type variable named temp

MYRCC_DeInit(); //Reset and configure the vector table. This function is automatically written by Keil, so you don't need to worry about it.

RCC->CR |= 0x00010000; //Set the 16th bit of the clock control register of stm32 to 1 to enable the external clock (HSE). For details, see the description of the RCC_CR register on page 85 of the STM32 reference manual.

while(! (RCC->CR>>17)); //Judge the 17th bit of the RCC_CR register, that is, whether the external high-speed clock is ready

RCC->CFGR = 0x00000400; //Set the 10th to 8th bits of the clock configuration register to make the APB1 clock not exceed 36MHz to prevent system disorder caused by APB1 clock exceeding 36MHz

PLL-=2; //Subtract 2 from the PLL value to configure the system's phase-locked loop frequency multiplication factor. For specific requirements, see bits 21-18 of the RCC_CFGR register.

RCC_CFGR |=(PLL<<18); // Shift the PLL value minus 2 by 18 bits and perform an OR operation with the original RCC_CFGR value to configure the PLL value.

RCC_CFGR|=(1<<16); //Use external clock as system clock

FLASH_ACR |= 0x32; //Delay FLASH by two cycles. For details, refer to the ST document PM0042 programming manual "STM32F10XXX Flash Programming"

RCC_CR |= 0x01000000; // Enable PLL

while(!(RCC->CR>>25)); //Judge whether PLL is enabled successfully

RCC_CFGR |= 0x0000002; //Use PLL output as system clock

while(temp!=0x02) { //Wait for PLL output to be set as system clock successfully

temp=RCC-CFGR>>2;

temp&=0x03;

}

}