基于GD32F303RCT6芯片 通过PWM与DMA结合硬件控制呼吸灯，用C语言写一份代码

以下是基于GD32F303RCT6芯片的PWM与DMA结合硬件控制呼吸灯的C语言代码示例：

#include "gd32f30x.h"

#define LED_PIN GPIO_PIN_5
#define LED_PORT GPIOB

#define PWM_CHANNEL TIMER_CH_1

#define PWM_FREQ 1000
#define LED_MAX_BRIGHTNESS 200

uint16_t dma_buffer[2];

void init_gpio(void)
{
    rcu_periph_clock_enable(RCU_GPIOB);
    gpio_init(LED_PORT, GPIO_MODE_AF_PP, GPIO_OSPEED_50MHZ, LED_PIN);
}

void init_timer(void)
{
    rcu_periph_clock_enable(RCU_TIMER1);
    timer_oc_parameter_struct oc_initpara;
    timer_parameter_struct timer_initpara;

    timer_deinit(TIMER1);

    timer_struct_para_init(&timer_initpara);
    timer_initpara.prescaler = SystemCoreClock / PWM_FREQ - 1;
    timer_initpara.period = LED_MAX_BRIGHTNESS - 1;
    timer_initpara.clock_division = TIMER_CKDIV_DIV1;
    timer_initpara.align = TIMER_ALIGN_CENTER;
    timer_initpara.repetition_counter = 0;
    timer_init(TIMER1, &timer_initpara);

    timer_channel_output_struct_para_init(&oc_initpara);
    oc_initpara.output_compare_mode = TIMER_OC_MODE_PWM1;
    oc_initpara.output_polarity = TIMER_OC_POLARITY_HIGH;
    oc_initpara.oc_idle_state = TIMER_OC_IDLE_STATE_LOW;
    oc_initpara.compare = 0;
    timer_channel_output_config(TIMER1, PWM_CHANNEL, &oc_initpara);

    timer_channel_output_pulse_value_config(TIMER1, PWM_CHANNEL, 0);
    timer_channel_output_mode_config(TIMER1, PWM_CHANNEL, TIMER_OC_MODE_PWM1);
    timer_channel_output_shadow_config(TIMER1, PWM_CHANNEL, TIMER_OC_SHADOW_DISABLE);
    timer_primary_output_config(TIMER1, ENABLE);
    timer_enable(TIMER1);
}

void init_dma(void)
{
    dma_parameter_struct dma_initpara;
    rcu_periph_clock_enable(RCU_DMA0);

    dma_deinit(DMA0, DMA_CH1);

    dma_struct_para_init(&dma_initpara);
    dma_initpara.direction = DMA_MEMORY_TO_PERIPHERAL;
    dma_initpara.memory_addr = (uint32_t)&dma_buffer[0];
    dma_initpara.memory_width = DMA_MEMORY_WIDTH_16BIT;
    dma_initpara.periph_addr = (uint32_t)&TIMER_CAR(TIMER1);
    dma_initpara.periph_width = DMA_PERIPHERAL_WIDTH_16BIT;
    dma_initpara.number = 2;
    dma_initpara.priority = DMA_PRIORITY_HIGH;
    dma_initpara.periph_inc = DMA_PERIPH_INCREASE_DISABLE;
    dma_initpara.memory_inc = DMA_MEMORY_INCREASE_ENABLE;
    dma_initpara.circular_mode = DMA_CIRCULAR_MODE_ENABLE;
    dma_initpara.periph_handshake = DMA_REQUEST_5;
    dma_initpara.channel = DMA_CH1;
    dma_init(DMA0, DMA_CH1, &dma_initpara);

    dma_circulation_enable(DMA0, DMA_CH1);
    dma_memory_to_periph_mode_enable(DMA0, DMA_CH1);
    dma_channel_enable(DMA0, DMA_CH1);
}

void update_led_brightness(uint8_t brightness)
{
    dma_buffer[0] = (uint16_t)LED_MAX_BRIGHTNESS * brightness / 255;
    dma_buffer[1] = LED_MAX_BRIGHTNESS - dma_buffer[0];
}

int main(void)
{
    init_gpio();
    init_timer();
    init_dma();

    update_led_brightness(0);

    while (1) {
        for (uint8_t brightness = 0; brightness < 255; brightness++) {
            update_led_brightness(brightness);
            while (dma_get_flag(DMA0, DMA_CH1, DMA_FLAG_FTF) == RESET);
            dma_flag_clear(DMA0, DMA_CH1, DMA_FLAG_FTF);
        }

        for (uint8_t brightness = 255; brightness > 0; brightness--) {
            update_led_brightness(brightness);
            while (dma_get_flag(DMA0, DMA_CH1, DMA_FLAG_FTF) == RESET);
            dma_flag_clear(DMA0, DMA_CH1, DMA_FLAG_FTF);
        }
    }

    return 0;
}

在上面的代码中，我们首先定义了LED的GPIO引脚和端口。然后我们定义了PWM通道和频率，以及LED的最大亮度和DMA缓冲区。

在`init_gpio()`函数中，我们启用LED的GPIO端口并将其配置为复用推挽输出模式。

在`init_timer()`函数中，我们启用并配置计时器1作为PWM控制器，并将其输出连接到LED引脚。我们启用了PWM1模式和高低电平极性，并将占空比零值设置为0。

在`init_dma()`函数中，我们启用并配置DMA0通道1，将其设置为循环模式，并配置其数据方向为从存储器到外设。每次更新LED亮度时，我们将DMA缓冲区的前一半设置为当前亮度值，而将后一半设置为补码亮度值。

在`update_led_brightness()`函数中，我们将当前亮度值转化为计时器1的占空比，并将其写入DMA缓冲区中。

最后在`main()`函数中，我们循环设置LED的亮度值和等待DMA传输完成。通过这种方式，我们可以实现呼吸灯效果。