Tool chains For the STM32F4

#define  RCC_AHB1RSTR_GPIOARST               ((uint32_t)0x00000001)
#define  RCC_AHB1RSTR_GPIOBRST               ((uint32_t)0x00000002)
#define  RCC_AHB1RSTR_GPIOCRST               ((uint32_t)0x00000004)
#define  RCC_AHB1RSTR_GPIODRST               ((uint32_t)0x00000008)
#define  RCC_AHB1RSTR_GPIOERST               ((uint32_t)0x00000010)
#define  RCC_AHB1RSTR_GPIOFRST               ((uint32_t)0x00000020)
#define  RCC_AHB1RSTR_GPIOGRST               ((uint32_t)0x00000040)
#define  RCC_AHB1RSTR_GPIOHRST               ((uint32_t)0x00000080)
#define  RCC_AHB1RSTR_GPIOIRST               ((uint32_t)0x00000100)
#define  RCC_AHB1RSTR_CRCRST                 ((uint32_t)0x00001000)
#define  RCC_AHB1RSTR_DMA1RST                ((uint32_t)0x00200000)
#define  RCC_AHB1RSTR_DMA2RST                ((uint32_t)0x00400000)
#define  RCC_AHB1RSTR_ETHMACRST              ((uint32_t)0x02000000)
#define  RCC_AHB1RSTR_OTGHRST                ((uint32_t)0x10000000)

#include "stm32f4xx.h"    //Include main header for MCU

#define LED1 0x1000
#define LED2 0x2000
#define LED3 0x4000
#define LED4 0x8000

void delay(int ticks);    //Used for delays

void main()
{
  //Bits 1:0 (01) HSE oscillator selected as system clock
  RCC->CFGR = RCC_CFGR_SW_HSE;

  //Bit 3 GPIODEN: IO port D clock enable (1: IO port D clock enabled)
  RCC->AHB1ENR = RCC_AHB1ENR_GPIODEN;
  
  //Bit 16 HSEON: HSE clock enable (1: HSE oscillator ON)
  RCC->CR |= RCC_CR_HSEON;
  
  //Bit 17 HSERDY: HSE clock ready flag (1: HSE oscillator ready)
  while((RCC->CR & RCC_CR_HSERDY)==0);

  //GPIO port mode register (all PORTD = 01: General purpose output mode)
  GPIOD->MODER   = GPIO_MODER_MODER12_0 | GPIO_MODER_MODER13_0 | GPIO_MODER_MODER14_0 | GPIO_MODER_MODER15_0; 
  
  //GPIO port speed reg. (all portd = 10: 50 MHz Fast speed)
  GPIOD->OSPEEDR = GPIO_OSPEEDER_OSPEEDR12_1 | GPIO_OSPEEDER_OSPEEDR13_1 | GPIO_OSPEEDER_OSPEEDR14_1 | GPIO_OSPEEDER_OSPEEDR15_1;

  while(1)
  {
    //My Crap Delay (~500,000 clks)
    delay(50000);
    
    //GPIO port output data register (ALL HIGH)
    GPIOD->ODR = LED1 | LED2 | LED3 | LED4;  

    //My Crap Delay (~500,000 clks)
    delay(50000);
    
    //GPIO port output data register (ALL LOW)
    GPIOD->ODR &= ~(LED1 | LED2 | LED3 | LED4);

  }
}

void delay(int ticks)
{
  while(ticks--);
}

void initDiscovery(void)
{
  RCC->CR &= 0xf0f0ff04;   //Clear Register without changing reserved bits or Calibration
  
  RCC->PLLCFGR &= 0xf0bc0000; //Clear Register without changing reserved bits
  RCC->PLLCFGR |= 0x7402a04;  // PLLQ:7, PLLSRC:HSE, PLLP:2, PLLN:168,PLLM:4

  RCC->CFGR &= 0x300;       //Clear Register without changing reserved bits
  RCC->CFGR |= 0xc0689402;  //MCO2:PLL, MCO1:PLL, RTCPRE:8, PPRE2:2, PPRE1:4, SW:PLL

  RCC->CR |= 0x1010000;    //PLL ON, HSE ON

  while((RCC->CR & 0x2020000)==0);  //Wait for HSE and PLL to stabilize
  
  RCC->AHB1ENR &= 0x818bee00;  //Clear Register without changing reserved bits
  RCC->AHB1ENR |= 0x1ff;       //IO port A:I clock enable
  
  GPIOA->MODER = 0x55555555;    // ALL GPO (General Purpose Output)
  GPIOA->OSPEEDR = 0xaaaaaaaa;  //50Mhz Speed
  GPIOA->PUPDR = 0;             //NO PULL UP/DOWN

  GPIOB->MODER = 0x55555555;    // ALL GPO (General Purpose Output)
  GPIOB->OSPEEDR = 0xaaaaaaaa;  //50Mhz Speed
  GPIOB->PUPDR = 0;             //NO PULL UP/DOWN

  GPIOC->MODER = 0x55555555;    // ALL GPO (General Purpose Output)
  GPIOC->OSPEEDR = 0xaaaaaaaa;  //50Mhz Speed
  GPIOC->PUPDR = 0;             //NO PULL UP/DOWN

  GPIOD->MODER = 0x55555555;    // ALL GPO (General Purpose Output)
  GPIOD->OSPEEDR = 0xaaaaaaaa;  //50Mhz Speed
  GPIOD->PUPDR = 0;             //NO PULL UP/DOWN

  GPIOE->MODER = 0x55555555;    // ALL GPO (General Purpose Output)
  GPIOE->OSPEEDR = 0xaaaaaaaa;  //50Mhz Speed
  GPIOE->PUPDR = 0;             //NO PULL UP/DOWN

  GPIOF->MODER = 0x55555555;    // ALL GPO (General Purpose Output)
  GPIOF->OSPEEDR = 0xaaaaaaaa;  //50Mhz Speed
  GPIOF->PUPDR = 0;             //NO PULL UP/DOWN

  GPIOG->MODER = 0x55555555;    // ALL GPO (General Purpose Output)
  GPIOG->OSPEEDR = 0xaaaaaaaa;  //50Mhz Speed
  GPIOG->PUPDR = 0;             //NO PULL UP/DOWN

  GPIOH->MODER = 0x55555555;    // ALL GPO (General Purpose Output)
  GPIOH->OSPEEDR = 0xaaaaaaaa;  //50Mhz Speed
  GPIOH->PUPDR = 0;             //NO PULL UP/DOWN

  GPIOI->MODER = 0x55555555;    // ALL GPO (General Purpose Output)
  GPIOI->OSPEEDR = 0xaaaaaaaa;  //50Mhz Speed
  GPIOI->PUPDR = 0;             //NO PULL UP/DOWN

}