STM32F7xx外设驱动9-pwm（寄存器）

产生一个2K 占空比50%的pwm波形
// PWM输出  PB1
void PwmPhyConfig()
{
		//此部分需手动修改 IO 口设置
		RCC->APB1ENR |= 1<<1; //TIM3 时钟使能
		RCC->AHB1ENR |= 1<<1; //使能 PORTB 时钟
	
	  GPIOB->MODER |=  (2<<1*2);  //复用模式
	  GPIOB->OTYPER &= ~(1<<1);   //推挽
	  GPIOB->PUPDR |= (1<<1*2);   //上拉
    GPIOB->OSPEEDR |= (1<<1*2); //高速
	  GPIOB->AFR[0] |= (2<<1*4);  //GPIO_AF2_TIM3
	
	
		TIM3->ARR = pwm_arr;  //设定计数器自动重装值
		TIM3->PSC = pwm_psc;  //预分频器不分频
		TIM3->CCMR2 |= 6<<12; //CH4 PWM1 模式
		TIM3->CCMR2 |= 1<<11; //CH4 预装载使能
		TIM3->CCER  |= 1<<12; //OC4 输出使能
		TIM3->CCER  |= 1<<13; //OC4 低电平有效
		TIM3->CR1   |= 1<<7;  //ARPE 使能
		TIM3->CR1   |= 1<<0;  //使能定时器 3
		
		TIM3->CCR4 = 250;
}

/******************************pwm*************************************/
#define 	pwm_arr   (500-1)  //2K
#define  	pwm_psc   (108-1)  //1M


void PwmPhyConfig(void);
/**********************************************************************/