stmbl

/* Michael Pratt <michael@pratt.im> */

/* Generic system call library for STM32F4-DISCOVERY
 * Eliminates need for the huge STM libraries */

#include "system.h"

static void SetSysClock(void);

/* Options */
#define VECT_TAB_OFFSET         0x00                        /* Vector Table Offset (multiple of 0x200) */

/* PLL Options - See RM0090 Reference Manual pg. 95 */
#define PLL_M      8            /* PLL_VCO = (HSE_VALUE or HSI_VALUE / PLL_M) * PLL_N */
#define PLL_N      336
#define PLL_P      2            /* SYSCLK = PLL_VCO / PLL_P */
#define PLL_Q      7            /* USB OTG FS, SDIO and RNG Clock =  PLL_VCO / PLLQ */


/* System Initialization Functions */

void SystemInit(void) {
  SCB->CPACR |= ((3UL << 10*2)|(3UL << 11*2));  /* Set CP10 and CP11 to full access */
  
  /* Reset the RCC clock configuration to the default reset state ------------*/
  /* Set HSION bit */
  RCC->CR |= (uint32_t)0x00000001;

  /* Reset CFGR register */
  RCC->CFGR = 0x00000000;

  /* Reset HSEON, CSSON and PLLON bits */
  RCC->CR &= (uint32_t)0xFEF6FFFF;

  /* Reset PLLCFGR register */
  RCC->PLLCFGR = 0x24003010;

  /* Reset HSEBYP bit */
  RCC->CR &= (uint32_t)0xFFFBFFFF;

  /* Disable all interrupts */
  RCC->CIR = 0x00000000;

  /* Configure the System clock source, PLL Multiplier and Divider factors, 
     AHB/APBx prescalers and Flash settings ----------------------------------*/
  SetSysClock();

  /* Configure the Vector Table location add offset address ------------------*/
  SCB->VTOR = FLASH_BASE | VECT_TAB_OFFSET; /* Vector Table Relocation in Internal FLASH */
}

/* PLL (clocked by HSE) used as System clock source */
static void SetSysClock(void) {
    volatile uint32_t StartUpCounter = 0, HSEStatus = 0;

    /* Enable HSE */
    RCC->CR |= ((uint32_t)RCC_CR_HSEON);

    /* Wait till HSE is ready and if Time out is reached exit */
    do {
        HSEStatus = RCC->CR & RCC_CR_HSERDY;
        StartUpCounter++;
    } while((HSEStatus == 0) && (StartUpCounter != HSE_STARTUP_TIMEOUT));

    if ((RCC->CR & RCC_CR_HSERDY) != 0) {
        HSEStatus = (uint32_t)0x01;
    }
    else {
        HSEStatus = (uint32_t)0x00;
    }

    if (HSEStatus == (uint32_t)0x01) {
        /* Enable high performance mode, System frequency up to 168 MHz */
        RCC->APB1ENR |= RCC_APB1ENR_PWREN;
        PWR->CR |= PWR_CR_VOS;  

        /* HCLK = SYSCLK / 1*/
        RCC->CFGR |= RCC_CFGR_HPRE_DIV1;
          
        /* PCLK2 = HCLK / 2*/
        RCC->CFGR |= RCC_CFGR_PPRE2_DIV2;

        /* PCLK1 = HCLK / 4*/
        RCC->CFGR |= RCC_CFGR_PPRE1_DIV4;

        /* Configure the main PLL */
        /* PLL Options - See RM0090 Reference Manual pg. 95 */
        RCC->PLLCFGR = PLL_M | (PLL_N << 6) | (((PLL_P >> 1) -1) << 16) |
                       (RCC_PLLCFGR_PLLSRC_HSE) | (PLL_Q << 24);

        /* Enable the main PLL */
        RCC->CR |= RCC_CR_PLLON;

        /* Wait till the main PLL is ready */
        while((RCC->CR & RCC_CR_PLLRDY) == 0) {
        }

        /* Configure Flash prefetch, Instruction cache, Data cache and wait state */
        FLASH->ACR = FLASH_ACR_ICEN |FLASH_ACR_DCEN |FLASH_ACR_LATENCY_5WS;

        /* Select the main PLL as system clock source */
        RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_SW));
        RCC->CFGR |= RCC_CFGR_SW_PLL;

        /* Wait till the main PLL is used as system clock source */
        while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS ) != RCC_CFGR_SWS_PLL); {
        }
    }
    else { 
        /* If HSE fails to start-up, the application will have wrong clock
        configuration. User can add here some code to deal with this error */
    }
}


/* Exception Handlers */

void NMI_Handler(void) {
    /* Do nothing on NMI exception */
}

void HardFault_Handler(void) {
  /* Go to infinite loop when Hard Fault exception occurs */
  while (1) {
  }
}

void MemManage_Handler(void) {
  /* Go to infinite loop when Memory Manage exception occurs */
  while (1) {
  }
}

void BusFault_Handler(void) {
  /* Go to infinite loop when Bus Fault exception occurs */
  while (1) {
  }
}

void UsageFault_Handler(void) {
  /* Go to infinite loop when Usage Fault exception occurs */
  while (1) {
  }
}

void SVC_Handler(void) {
    /* Do nothing on SVCall exception */
}

void DebugMon_Handler(void) {
    /* Do nothing on Debug Monitor exception */
}

void PendSV_Handler(void) {
    /* Do nothing on PendSVC exception */
}

void SysTick_Handler(void) {
    /* Do nothing on SysTick */
}