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#include "rcc.h"
#include "flash.h"
#include "../syscfg/syscfg.h"
void rcc_init() {
// Initialize flash.
flash_init();
#if defined(STM32F1) || defined(STM32F3)
// Enable (assumed 8MHz!) HSE
RCC->CR |= 0x10000;
while(!(RCC->CR & 0x20000));
// Configure and enable PLL from HSE.
auto pll_mul = 9;
RCC->CFGR = ((pll_mul-2)<<18) | (0x2 << 15);
RCC->CR |= 0x1000000;
while(!(RCC->CR & 0x2000000));
// Switch to PLL.
RCC->CFGR |= 0x2;
while(!(RCC->CFGR & 0x8));
// Set APB1 prescaler to /2.
RCC->CFGR |= 0x400;
// Set ADCCLK prescaler to /6. => 12MHz is ~sufficient
#if defined(STM32F1)
RCC->CFGR |= 0x8000;
#else
RCC->CFGR2 = (0b10011 << 9) | (0b10011 << 4);
#endif
#elif defined(STM32F4)
// Enable HSE.
RCC->CR |= 0x10000;
while(!(RCC->CR & 0x20000));
// Configure and enable PLL.
RCC->PLLCFGR = 0x20400000 | (7 << 24) | (2 * 168 << 6) | 8;
RCC->CR |= 0x1000000;
while(!(RCC->CR & 0x2000000));
// Switch to PLL.
RCC->CFGR |= 0x2;
while(!(RCC->CFGR & 0x8));
// Set APB1 prescaler to /4.
RCC->CFGR |= 5 << 10;
// Set APB2 prescaler to /2.
RCC->CFGR |= 4 << 13;
#elif defined(STM32F0)
// Enable HSI48.
RCC->CR2 |= 1 << 16; // HSI48ON
while(!(RCC->CR2 & (1 << 17))); // HSI48RDY
// Switch to HSI48.
RCC->CFGR |= 3 << 0; // SW = HSI48
while((RCC->CFGR & (3 << 2)) != (3 << 2)); // SWS = HSI48
#elif defined(STM32L0)
// Enable HSI16.
RCC->CR |= 1 << 0; // HSI16ON
while(!(RCC->CR & (1 << 2))); // HSI16RDYF
// Configure PLL.
RCC->CFGR |= (1 << 22) | (1 << 18) | (0 << 16); // PLLDIV = /2, PLLMUL = 4x, PLLSRC = HSI16
// Enable PLL.
RCC->CR |= 1 << 24; // PLLON
while(!(RCC->CR & (1 << 25))); // PLLRDY
// Switch to PLL.
RCC->CFGR |= 3 << 0; // SW = PLL
while((RCC->CFGR & (3 << 2)) != (3 << 2)); // SWS = PLL
// Enable VREFINT for HSI48.
RCC->enable(RCC->SYSCFG);
SYSCFG.CFGR3 |= (1 << 13) | (1 << 0); // ENREF_HSI48, EN_VREFINT
while(!(SYSCFG.CFGR3 & (1 << 26))); // REF_HSI48_RDYF
// Enable HSI48.
RCC->CRRCR |= 1 << 0; // HSI48ON
while(!(RCC->CRRCR & (1 << 1))); // HSI48RDY
// Select HSI48 for USB.
RCC->CCIPR |= 1 << 26;
#endif
}
#if defined(STM32F4)
void rcc_init(uint32_t osc_mhz, uint32_t sysclk_mhz) {
// Initialize flash.
flash_init();
uint32_t pll_mhz = sysclk_mhz > 192 / 2 ? sysclk_mhz * 2 : sysclk_mhz * 4;
uint32_t pllp = sysclk_mhz > 192 / 2 ? 0 : 1;
// Enable HSE.
RCC->CR |= 0x10000;
while(!(RCC->CR & 0x20000));
// Configure and enable PLL.
RCC->PLLCFGR = 0x20400000 | ((pll_mhz / 48) << 24) | (pllp << 16) | (pll_mhz << 6) | osc_mhz;
RCC->CR |= 0x1000000;
while(!(RCC->CR & 0x2000000));
// Switch to PLL.
RCC->CFGR |= 0x2;
while(!(RCC->CFGR & 0x8));
if(sysclk_mhz > 84) {
// Set APB1 prescaler to /4.
RCC->CFGR |= 5 << 10; // PPRE1
// Set APB2 prescaler to /2.
RCC->CFGR |= 4 << 13; // PPRE2
} else {
// Set APB1 prescaler to /2.
RCC->CFGR |= 4 << 10; // PPRE1
// Set APB2 prescaler to /1.
RCC->CFGR |= 0 << 13; // PPRE2
}
}
#endif
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