【GD32F310开发板试用】定时器产生PWM实现呼吸灯

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号其实类似于方波，只有0和1两种状态。PWM信号可以调节占空比。
不同占空比可以使LED产生不同的亮度。占空比就是指在一个周期内， 信号处于高电平的时间占据整个信号周期的百分比；PWM波可以由GPIO口产生，通过GPIO口输出高电平，延时，输出低电平，延时来产生PWM波。还可以使用定时器，利用比较寄存器形成PWM。

我这次就使用定时器来实现呼吸灯。

在实现呼吸灯之前，我们首先了解一下板子的原理图和芯片的datasheet，
在原理图中，可以看出led连接着PA8,而在datasheet中可以看到PA8可以(Altermate)复用为定时器0的通道0，也就是TIMER0_CH0；有这个基础后，我们就可以很愉快地写代码啦

代码部分
/配置 PA8(TIMER_CH0) 为定时器通道0的复用/
`

void gpio_config(void){rcu_periph_clock_enable(RCU_GPIOA);/*Configure PA8(TIMER0_CH0) as alternate function*/gpio_mode_set(GPIOA, GPIO_MODE_AF, GPIO_PUPD_NONE, GPIO_PIN_8);gpio_output_options_set(GPIOA, GPIO_OTYPE_PP, GPIO_OSPEED_50MHZ,GPIO_PIN_8);gpio_af_set(GPIOA, GPIO_AF_2, GPIO_PIN_8);}`/配置定时器/`void timer_config(void){/* TIMER0 configuration: generate PWM signals with different duty cycles:   TIMER0CLK = SystemCoreClock / 72 = 1MHz */timer_oc_parameter_struct timer_ocintpara;timer_parameter_struct timer_initpara;rcu_periph_clock_enable(RCU_TIMER0);timer_deinit(TIMER0);/* TIMER0 configuration */timer_initpara.prescaler  = 71;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(TIMER0,&timer_initpara); /* CH0 configuration in PWM mode */timer_ocintpara.outputstate  = TIMER_CCX_ENABLE;timer_ocintpara.outputnstate = TIMER_CCXN_DISABLE;timer_ocintpara.ocpolarity   = TIMER_OC_POLARITY_HIGH;timer_ocintpara.ocnpolarity  = TIMER_OCN_POLARITY_HIGH;timer_ocintpara.ocidlestate  = TIMER_OC_IDLE_STATE_LOW;timer_ocintpara.ocnidlestate = TIMER_OCN_IDLE_STATE_LOW;timer_channel_output_config(TIMER0,TIMER_CH_0,&timer_ocintpara);timer_channel_output_pulse_value_config(TIMER0,TIMER_CH_0,250);timer_channel_output_mode_config(TIMER0,TIMER_CH_0,TIMER_OC_MODE_PWM0);timer_channel_output_shadow_config(TIMER0,TIMER_CH_0,TIMER_OC_SHADOW_DISABLE);timer_primary_output_config(TIMER0,ENABLE);/* auto-reload preload enable */timer_auto_reload_shadow_enable(TIMER0);timer_enable(TIMER0);}`

主函数：

`int main(void){int a; int16_t i = 0;FlagStatus breathe_flag = SET;systick_config(); HW_UsartInit();    /* configure the GPIO ports */gpio_config(); timer_config();while(1){  /* delay a time in milliseconds */    delay_1ms(40);    if (SET == breathe_flag){  i = i + 10;    }else{ i = i - 10;    }    if(500 = i){ breathe_flag = SET;    }    /* configure TIMER channel output pulse value */    timer_channel_output_pulse_value_config(TIMER0,TIMER_CH_0,i);}}`gitee:https://gitee.com/myBoolean/g...