ref: 385ecf9c11ba7114801e877090951e1785698051
dir: /clock.c/
#include <u.h>
#include "dat.h"
#include "fns.h"
#include "include/stm32f103xb.h"
/*
* SYSCLK has PLL as a source. The PLL is driven by the HSE,
* with a x4 multiplier. The crystal is 8MHz, meaning,
* 32MHz system ticks.
*/
void
clockinit()
{
/* configure AHB and APB GPIO ports */
RCC->APB1ENR |= RCC_APB1ENR_USART2EN; // USART2
RCC->APB2ENR |= RCC_APB2ENR_IOPAEN | // PORTA
RCC_APB2ENR_IOPCEN | // PORTC
RCC_APB2ENR_USART1EN | // USART1
RCC_APB2ENR_AFIOEN; // AFIO
RCC->AHBENR |= RCC_AHBENR_DMA1EN; // DMA
/* Clear CIR flags */
RCC->CIR = RCC_CIR_HSIRDYF |
RCC_CIR_HSERDYF |
RCC_CIR_PLLRDYF |
RCC_CIR_CSSF |
RCC_CIR_CSSC;
/* Set HSEON bit */
RCC->CR = RCC_CR_HSEON;
while(!(RCC->CR | RCC_CR_HSERDY));
/* configure, enable PLL and wait */
RCC->CFGR = RCC_CFGR_PLLSRC | // PLL source
RCC_CFGR_PLLMULL6 | // PLL multiplication x6
RCC_CFGR_PPRE1_DIV2 | // PPRE1 not divided
RCC_CFGR_PPRE2_DIV2 | // PPRE2 not divided
RCC_CFGR_HPRE_DIV1; // HPRE divided by 2
RCC->CR |= RCC_CR_PLLON;
while(!(RCC->CR & RCC_CR_PLLRDY));
/* select PLL as clock source */
RCC->CFGR = (RCC->CFGR & ~RCC_CFGR_SW_PLL) | RCC_CFGR_SW_PLL;
while(!(RCC->CFGR & RCC_CFGR_SWS_PLL));
}
void
_wait(ulong useconds)
{
// Since each tick is 1/64MHz = 7.8
for(int i = 0; i < useconds; i++) {
for(int j = 0; j < 12; j++);
}
}