ESP32如何使用SPI的DMA?

ESP32 使用 SPI DMA 的方法如下：

1. 首先，确保你已经安装了 ESP-IDF 4.3 版本。如果你还没有安装，请访问 https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/index.html#installation-step-by-step 按照步骤安装。

2. 创建一个新的 ESP-IDF 项目。你可以使用以下命令创建一个名为 "spi_dma_example" 的项目：

```
mkdir spi_dma_example
cd spi_dma_example
mkdir components
cp -r /path/to/esp-idf/examples/peripherals/spi/spi_master/components/spi_master .
cp -r /path/to/esp-idf/examples/peripherals/spi/spi_master/main .
cp -r /path/to/esp-idf/examples/peripherals/spi/spi_master/CMakeLists.txt .
cp -r /path/to/esp-idf/examples/peripherals/spi/spi_master/idf_component.yml .
```

3. 打开 "spi_master" 组件目录，找到 "spi_master.c" 文件。在这个文件中，你需要添加 DMA 相关的代码。以下是一个示例代码片段：

```c
#include "driver/spi_master.h"
#include "driver/dma.h"

// ...

void spi_dma_example() {
    // 初始化 SPI 和 DMA
    spi_bus_config_t bus_cfg = {
        .mosi_io_num = SPI_MASTER_MOSI_GPIO,
        .miso_io_num = SPI_MASTER_MISO_GPIO,
        .sclk_io_num = SPI_MASTER_SCLK_GPIO,
        .quadwp_io_num = -1,
        .quadhd_io_num = -1,
    };
    spi_device_interface_config_t dev_cfg = {
        .clock_speed_hz = 10 * 1000 * 1000, // 10 MHz
        .mode = 0,
        .spics_io_num = SPI_CS_GPIO,
        .queue_size = 7,
        .pre_cb = NULL,
    };
    spi_bus_initialize(HSPI_HOST, &bus_cfg, 1);
    spi_device_handle_t spi;
    spi_device_create(HSPI_HOST, &dev_cfg, &spi);

    // 初始化 DMA
    lldesc_t dma_desc[2];
    memset(&dma_desc[0], 0, sizeof(dma_desc));
    dma_desc[0].length = 4096;
    dma_desc[0].size = 4096;
    dma_desc[0].buf = (uint8_t *)malloc(4096);
    dma_desc[0].eof = 1;
    dma_desc[1].length = 0;
    dma_desc[1].size = 0;
    dma_desc[1].buf = NULL;
    dma_desc[1].eof = 1;
    dma_descriptor_enable(1, 0, 0, 0, 0, 0);
    dma_set_owner(1, 0, 0);
    dma_reset_channel(1, 0);

    // 配置 SPI DMA
    spi_transaction_t t;
    memset(&t, 0, sizeof(t));
    t.length = 4096 * 8;
    t.tx_buffer = dma_desc[0].buf;
    spi_device_queue_trans(spi, &t, portMAX_DELAY);

    // 启动 DMA
    dma_setup_link(1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0