gd32F470如何输出一个PWM波形（呼吸灯）

pwm.c

#include "pwm.h"

void pwm_init(void)
{
	timer_parameter_struct timer_initpara;
    timer_oc_parameter_struct timer_ocintpara;
	
	//PC9配置为复用推挽输出
	rcu_periph_clock_enable(RCU_GPIOC);
	gpio_mode_set(GPIOC, GPIO_MODE_AF, GPIO_PUPD_NONE,GPIO_PIN_9);
    gpio_output_options_set(GPIOC, GPIO_OTYPE_PP, GPIO_OSPEED_50MHZ,GPIO_PIN_9);
	gpio_af_set(GPIOC, GPIO_AF_2, GPIO_PIN_9);
	
    rcu_periph_clock_enable(RCU_TIMER2);
    rcu_timer_clock_prescaler_config(RCU_TIMER_PSC_MUL4);
    timer_struct_para_init(&timer_initpara);
    timer_deinit(TIMER2);

    /* TIMER2 configuration */
    timer_initpara.prescaler         = 119;
    timer_initpara.alignedmode       = TIMER_COUNTER_EDGE;
    timer_initpara.counterdirection  = TIMER_COUNTER_UP;
    timer_initpara.period            = 500;
    timer_initpara.clockdivision     = TIMER_CKDIV_DIV1;
    timer_initpara.repetitioncounter = 0;
    timer_init(TIMER2,&timer_initpara);

    /* CH3 configuration in PWM mode 0 */
    timer_channel_output_struct_para_init(&timer_ocintpara);
    timer_ocintpara.ocpolarity  = TIMER_OC_POLARITY_HIGH;
    timer_ocintpara.outputstate = TIMER_CCX_ENABLE;
    timer_ocintpara.ocnpolarity  = TIMER_OCN_POLARITY_HIGH;
    timer_ocintpara.outputnstate = TIMER_CCXN_DISABLE;
    timer_ocintpara.ocidlestate  = TIMER_OC_IDLE_STATE_LOW;
    timer_ocintpara.ocnidlestate = TIMER_OCN_IDLE_STATE_LOW;

    timer_channel_output_config(TIMER2,TIMER_CH_3,&timer_ocintpara);

    /* CH3 configuration in PWM mode 0,duty cycle 25% */
    timer_channel_output_pulse_value_config(TIMER2,TIMER_CH_3,0);
    timer_channel_output_mode_config(TIMER2,TIMER_CH_3,TIMER_OC_MODE_PWM0);
    timer_channel_output_shadow_config(TIMER2,TIMER_CH_3,TIMER_OC_SHADOW_DISABLE);

    /* auto-reload preload enable */
    timer_auto_reload_shadow_enable(TIMER2);
    /* TIMER1 enable */
    timer_enable(TIMER2);
}

pwm.h 

#ifndef __PWM_H
#define __PWM_H

#include "head.h"

void pwm_init(void);


#endif

主函数

	pwm_init();
	
	while(1)
	{
		for(int i=0;i<500;i++)
		{
			timer_channel_output_pulse_value_config(TIMER2,TIMER_CH_3,i);
			delay_1ms(1);
		}
		for(int i=500;i>0;i--)
		{
			timer_channel_output_pulse_value_config(TIMER2,TIMER_CH_3,i);
			delay_1ms(1);
		}
	}