#include "stdint.h"

// RCC
#define  RCC_APB1ENR *((volatile uint32_t*)0x4002101C)
#define  RCC_APB2ENR *((volatile uint32_t*)0x40021018)

// GPIOA
#define  GPIOA_CRL   *((volatile uint32_t*)0x40010800)
#define  GPIOA_ODR   *((volatile uint32_t*)0x4001080C)
	
// TIMER
#define TIM2_CR1      *((volatile uint32_t*) 0x40000000)
#define TIM2_CCMR1    *((volatile uint32_t*) 0x40000018)
#define TIM2_CCMR2    *((volatile uint32_t*) 0x4000001C)
#define TIM2_CCER     *((volatile uint32_t*) 0x40000020)
#define TIM2_PSC      *((volatile uint32_t*)  0x40000028)
#define TIM2_ARR      *((volatile uint32_t*)  0x4000002C)
	
#define TIM2_CCR1     *((volatile uint32_t*) 0x40000034)
#define TIM2_CCR2     *((volatile uint32_t*) 0x40000038)
#define TIM2_CCR3     *((volatile uint32_t*) 0x4000003C)
#define TIM2_CCR4     *((volatile uint32_t*) 0x40000040)


void delay(uint32_t t)
{
    for(uint32_t i=0;i<t*500;i++)
    {
        __asm("nop");
    }
}
void Timx_init (void)
{
	//turn on GPIOA
	RCC_APB2ENR |=(1<<2);
	//turn on TIM2
	RCC_APB1ENR |=(1<<0);
	// config PA0,1,2 is Alternate Function for TIM2_CH1,2,3,4
	/*MODE = 11  (output 50MHz)
    CNF  = 10  (alternate function push pull)
    =>0xB
  */
	GPIOA_CRL &=~(0xFFFF);
	GPIOA_CRL |=  (0xBBBB);
	// config prescaler timer 
	TIM2_PSC = 71; // 1MHZ
	// config previous PWM
	TIM2_ARR = 255;
	// config PWM mode for CH1 CH2 CH3 CH4
	/*OC1M = 110 -> PWM mode 1
    OC2M = 110 -> PWM mode 1
	  OC3M = 110 -> PWM mode 1
	  OC4M = 110 -> PWM mode 1
  */
	TIM2_CCMR1 &= ~((7<<4)|(7<<12));
	TIM2_CCMR2 &= ~((7<<4)|(7<<12));
	TIM2_CCMR1 |= (6<<4)|(6<<12);
	TIM2_CCMR2 |= (6<<4)|(6<<12);
	// enable output preload
	TIM2_CCMR1 |= (1<<3)|(1<<11);
  TIM2_CCMR2 |= (1<<3)|(1<<11);
	// enable output for CH1 CH2 CH3 CH4
	TIM2_CCER  |= (1<<0)|(1<<4)|(1<<8)|(1<<12);
	// set first duty
	TIM2_CCR1 = 0 ;
	TIM2_CCR2 = 0 ;
	TIM2_CCR3 = 0 ;
	TIM2_CCR4 = 0 ;
	// turn on Timer
	TIM2_CR1 |= (1|(1<<7)); 
}

void set_duty(uint8_t channel, uint8_t duty)
{
    uint32_t CCR_value = (duty * TIM2_ARR) / 100;

    switch(channel)
    {
        case 1:
            TIM2_CCR1 = CCR_value;
            break;

        case 2:
            TIM2_CCR2 = CCR_value;
            break;

        case 3:
            TIM2_CCR3 = CCR_value;
            break;

        case 4:
            TIM2_CCR4 = CCR_value;
            break;
    }
}

int main (void)
{
	Timx_init();
	while(1)
	{
	for ( int i=0 ; i<100;i++)
	 {
      // set_duty(1,100-i);
			// set_duty(2,i);
			// set_duty(3,100-i/2);
			TIM2_CCR1 = 255-i;
      TIM2_CCR2 = i;
      TIM2_CCR3 = 255 - i/2;
	    delay(20);
	 }
	}
	
}