GD32F303 DAC输出方波

要在GD32F303上使用DAC输出方波，可以按照以下步骤进行：

1. 初始化DAC模块并设置为触发模式：在DAC初始化代码中，需要设置DAC模块为触发模式。触发模式下，DAC会按照指定的触发源来输出模拟信号。可以选择软件触发或者外部触发。在这里，我们选择软件触发。

DAC_InitPara.DAC_Trigger = DAC_TRIGGER_SOFTWARE;
DAC_InitPara.DAC_WaveGeneration = DAC_WAVE_GENERATION_NONE;
DAC_InitPara.DAC_OutputBuffer = DAC_OUTPUT_BUFFER_ENABLE;
DAC_Init(DAC1, &DAC_InitPara);

2. 设置DAC输出DMA：使用DMA可以让DAC在后台输出数据，而不需要CPU的干预。在这里，我们将DAC的数据寄存器与DMA通道相连。

DMA_InitPara.DMA_PeripheralBaseAddr = (uint32_t)(&DAC1->DAT);
DMA_InitPara.DMA_MemoryBaseAddr = (uint32_t)WaveTab;
DMA_InitPara.DMA_DIR = DMA_DIR_PERIPHERALDST;
DMA_InitPara.DMA_BufferSize = WAVE_TAB_SIZE;
DMA_InitPara.DMA_PeripheralInc = DMA_PERIPHERALINC_DISABLE;
DMA_InitPara.DMA_MemoryInc = DMA_MEMORYINC_ENABLE;
DMA_InitPara.DMA_PeripheralDataSize = DMA_PERIPHERALDATASIZE_HALFWORD;
DMA_InitPara.DMA_MemoryDataSize = DMA_MEMORYDATASIZE_HALFWORD;
DMA_InitPara.DMA_Mode = DMA_MODE_CIRCULAR;
DMA_InitPara.DMA_Priority = DMA_PRIORITY_HIGH;
DMA_InitPara.DMA_MTOM = DMA_MEMTOMEM_DISABLE;

3. 填充DAC输出数据：在这里，我们将DAC的输出数据设置为一个方波。可以根据需要修改方波的频率和占空比。

for(i = 0; i < WAVE_TAB_SIZE; i++)
{
    if(i < WAVE_TAB_SIZE / 2)
    {
        WaveTab[i] = 0;
    }
    else
    {
        WaveTab[i] = 0xFFF;
    }
}

4. 启动DAC输出DMA：启动DMA后，DAC会自动输出数据。

DMA_Enable(DMA_CHANNEL_0, ENABLE);
DAC_Enable(DAC1, ENABLE);

完整的代码示例可以参考以下代码：

#include "gd32f30x.h"
#include "systick.h"

#define WAVE_TAB_SIZE 256

uint16_t WaveTab[WAVE_TAB_SIZE];

void DAC_Configuration(void)
{
    DAC_InitPara DAC_InitPara;
    DMA_InitPara DMA_InitPara;
    uint16_t i;

    RCC_AHBPeriphClock_Enable(RCC_AHBPERIPH_DMA0, ENABLE);
    RCC_APB1PeriphClock_Enable(RCC_APB1PERIPH_DAC, ENABLE);

    DAC_InitPara.DAC_Trigger = DAC_TRIGGER_SOFTWARE;
    DAC_InitPara.DAC_WaveGeneration = DAC_WAVE_GENERATION_NONE;
    DAC_InitPara.DAC_OutputBuffer = DAC_OUTPUT_BUFFER_ENABLE;
    DAC_Init(DAC1, &DAC_InitPara);

    for(i = 0; i < WAVE_TAB_SIZE; i++)
    {
        if(i < WAVE_TAB_SIZE / 2)
        {
            WaveTab[i] = 0;
        }
        else
        {
            WaveTab[i] = 0xFFF;
        }
    }

    DMA_InitPara.DMA_PeripheralBaseAddr = (uint32_t)(&DAC1->DAT);
    DMA_InitPara.DMA_MemoryBaseAddr = (uint32_t)WaveTab;
    DMA_InitPara.DMA_DIR = DMA_DIR_PERIPHERALDST;
    DMA_InitPara.DMA_BufferSize = WAVE_TAB_SIZE;
    DMA_InitPara.DMA_PeripheralInc = DMA_PERIPHERALINC_DISABLE;
    DMA_InitPara.DMA_MemoryInc = DMA_MEMORYINC_ENABLE;
    DMA_InitPara.DMA_PeripheralDataSize = DMA_PERIPHERALDATASIZE_HALFWORD;
    DMA_InitPara.DMA_MemoryDataSize = DMA_MEMORYDATASIZE_HALFWORD;
    DMA_InitPara.DMA_Mode = DMA_MODE_CIRCULAR;
    DMA_InitPara.DMA_Priority = DMA_PRIORITY_HIGH;
    DMA_InitPara.DMA_MTOM = DMA_MEMTOMEM_DISABLE;

    DMA_Init(DMA_CHANNEL_0, &DMA_InitPara);

    DMA_Enable(DMA_CHANNEL_0, ENABLE);
    DAC_Enable(DAC1, ENABLE);
}

int main(void)
{
    SysTick_Init();

    DAC_Configuration();

    while (1)
    {
        delay_1ms(10);
    }
}