untitled

void system_clk()
{
	//ENABLE HSE & WAIT FOR HSE TO BECOME READY
	RCC->CR |= RCC_CR_HSEON ;   // HSE IS 8MHZ
	while(!(RCC->CR & RCC_CR_HSERDY))
		 ;
	//configure flash prefetch and the latency related
	FLASH->ACR |= FLASH_ACR_PRFTBE|FLASH_ACR_LATENCY_1;
	// CONFIGURE PLL AND Buses(AHB,APB1,APB2)
	//PLL SOURCE: HERE  HSE IS USED AS SOURCE
	RCC->CFGR |= RCC_CFGR_PLLSRC;
	//HSE DEVIDER FOR PLL(IF HSE IS USED AS SOURCE FOR PLL) : NOT DIVIDING CLOCK
	RCC->CFGR |= RCC_CFGR_PLLXTPRE_HSE ;  // SO INPUT TO PLL IS 8MHZ
	//PLL MULTIPLIER: HERE I AM MULTIPLYING HSE OUTPUT WITH 4
	RCC->CFGR |= RCC_CFGR_PLLMULL4; //SO OUTPUT FROM PLL IS 32MHZ
	//BUS CLOCK CONFIGURE(APB1,APB2,AHB): NOT DIVIDING
	RCC->CFGR |= (RCC_CFGR_PPRE1_DIV1 | RCC_CFGR_PPRE2_DIV1 | RCC_CFGR_HPRE_DIV1);  // all buses runs at 32MHZ
	//ENABLE THE PLL
	RCC->CR |= RCC_CR_PLLON;
	//WAIT FOR PLL TO SET
	while(!(RCC->CR & RCC_CR_PLLRDY))
			;

	 //ENABLE SYSTEMCLK AND WAIT
	 RCC->CFGR |= RCC_CFGR_SW_HSE;
	 while(!(RCC->CFGR & RCC_CFGR_SWS_HSE))
	 		 ;

	 MCO_pin_conf();
	 //CLOCK OUTPUT ON MCO PIN
	 RCC->CFGR |= RCC_CFGR_MCO_SYSCLK;
}

/* Timer Frequency(TF) = System Clock(Fsysclk)/Prescalor(TIM2PSC)
 *
 * Timer time Period(TTP) = 1/timer frequency(TF)
 *
 * Time delay by timer = Timer Time Period(TTP) * Timer auto reload register(TIM2ARR)
 *
 * System Clock = 32Mhz, TIM2PSC = 65535, So TF = 489hz
 *
 * TTP = 0.002sec
 * TIM2ARR = 500, so timer delay = 0.002*500
 *
 */
void timer_initialise()
{
	// Start by making sure the timer's 'counter' is off
	TIM2->CR1 &= ~(TIM_CR1_CEN);

	//RESET THE TIMER2 BUS
	RCC->APB1RSTR |=  (RCC_APB1RSTR_TIM2RST);
	RCC->APB1RSTR &= ~(RCC_APB1RSTR_TIM2RST);
	//Enable Timer2 peripheral clock
    RCC->APB1ENR |= RCC_APB1ENR_TIM2EN;

    //Timer prescaler value
    TIM2->PSC =65535;
    //Timer Auto reload register value
    TIM2->ARR = 500;
    //Select the UEV event Source
    TIM2->CR1 |= (TIM_CR1_URS) | (~TIM_CR1_UDIS); // Only counter overflow/underflow generates an update

    //Enable the update generation
    TIM2->EGR |= TIM_EGR_UG;

    // Enable the NVIC interrupt for TIM2.
    //NVIC_EnableIRQ(TIM2_IRQn);
    //NVIC_SetPriority(TIM2_IRQn, 0x03);

    //Enable the Update Interrupt
    // TIM2->DIER |= TIM_DIER_UIE;


}
void delay()
{
	TIM2->CR1 |= TIM_CR1_CEN;
	while(!(TIM2->SR & TIM_SR_UIF));
	{
		//Enable the update generation
	    TIM2->EGR |= TIM_EGR_UG;
	TIM2->CR1 &= ~TIM_CR1_CEN;
	}
}
int main(void)
{

	 system_clk();
     //ENABLE GPIO CLOCK
	 Gpio_output_pushpull_conf();
	 //Init Timer for time base unit
	 timer_initialise();

	while(1)
	{
		GPIOC->ODR ^= (GPIO_ODR_ODR13);
        delay();

	}
}