GD32F450使用定时器溢出作为DMA触发源

GD32F450可以使用定时器的溢出事件作为DMA的触发源。具体实现步骤如下：

1. 配置定时器溢出事件触发DMA请求。

2. 配置DMA传输相关参数，包括源地址、目的地址、数据长度等。

3. 启动定时器和DMA传输。

代码示例：

// 配置定时器溢出事件触发DMA请求
timer_oc_parameter_struct timer_ocinitpara;
timer_parameter_struct timer_initpara;

rcu_periph_clock_enable(RCU_TIMER0);
rcu_timer_clock_prescaler_config(RCU_TIMER_PSC_MUL4);  // 定时器时钟预分频

timer_deinit(TIMER0);
timer_struct_para_init(&timer_initpara);
timer_initpara.prescaler         = 3999;  // 计数器时钟为 108 MHz / (3999 + 1) = 27 kHz
timer_initpara.alignedmode       = TIMER_COUNTER_EDGE;
timer_initpara.counterdirection  = TIMER_COUNTER_UP;
timer_initpara.period            = 1000;  // 定时器溢出时间为 1000 / 27 kHz ≈ 37.04 us
timer_init(TIMER0, &timer_initpara);

timer_oc_struct_para_init(&timer_ocinitpara);
timer_ocinitpara.ocmode      = TIMER_OC_MODE_TIMING;
timer_ocinitpara.pulse       = 0xFFFF;
timer_ocinitpara.outputstate = TIMER_CCX_ENABLE;
timer_ocinitpara.ocpolarity  = TIMER_OC_POLARITY_HIGH;
timer_oc_config(TIMER0, TIMER_CH_0, &timer_ocinitpara);

dma_parameter_struct dma_initpara;
dma_struct_para_init(&dma_initpara);

rcu_periph_clock_enable(RCU_DMA0);
dma_deinit(DMA0, DMA_CH0);
dma_initpara.direction         = DMA_MEMORY_TO_MEMORY;
dma_initpara.memory_addr       = (uint32_t)src_buffer;
dma_initpara.memory_inc        = DMA_MEMORY_INCREASE_ENABLE;  // 源地址自增
dma_initpara.periph_addr       = (uint32_t)dst_buffer;
dma_initpara.periph_inc        = DMA_PERIPH_INCREASE_DISABLE;  // 目的地址不变
dma_initpara.memory_width      = DMA_MEMORY_WIDTH_8BIT;
dma_initpara.periph_width      = DMA_PERIPHERAL_WIDTH_8BIT;
dma_initpara.number            = sizeof(src_buffer) / sizeof(src_buffer[0]);
dma_initpara.priority          = DMA_PRIORITY_ULTRA_HIGH;
dma_initpara.fifo_mode         = DMA_FIFOMODE_DISABLE;
dma_initpara.periph_addr_cfg   = DMA_PERIPH_ADDR_INC;
dma_initpara.circular_mode    = DMA_CIRCULAR_MODE_ENABLE;
dma_initpara.memory_addr_cfg   = DMA_MEMORY_ADDR_INC;
dma_initpara.direction_cfg     = DMA_DIRECTION_PERIPH_TO_MEMORY;
dma_init(DMA0, DMA_CH0, &dma_initpara);

dma_circulation_disable(DMA0, DMA_CH0);  // 禁用 DMA 循环传输模式
dma_memory_to_memory_disable(DMA0, DMA_CH0);  // 禁用 DMA 存储器到存储器模式

dma_interrupt_enable(DMA0, DMA_CH0, DMA_INT_FTF);  // 开启 DMA 传输完成中断
nvic_irq_enable(DMA0_Channel0_IRQn, 0, 0);  // 开启 DMA 中断

timer_dma_transfer_config(TIMER0, TIMER_DMACFG_DMATA_CH0, TIMER_DMACFG_DMATC_UEV);  // 配置定时器溢出事件触发DMA请求
timer_enable(TIMER0);  // 启动定时器
dma_channel_enable(DMA0, DMA_CH0);  // 启动DMA传输

在以上代码中，我们通过`timer_dma_transfer_config`函数配置了定时器溢出事件触发DMA请求。在定时器溢出时，DMA请求将被触发，进而启动DMA传输。DMA传输完成后，将会触发DMA传输完成中断。