首先是初始化 I2S 设备中，可能用到了缓存
//初始化 I2S 设备 INMP441Serial.println("Setup I2S ...");i2s_install();i2s_setpin();esp_err_t err = i2s_start(I2S_PORT_0); 其中的 i2s_install() 配置了 i2s 的相关设置，函数具体内容如下：
/*** @brief 配置 i2s 参数* */
void i2s_install()
{const i2s_config_t i2s_config = {.mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX),.sample_rate = SAMPLE_RATE,.bits_per_sample = i2s_bits_per_sample_t(16),.channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,.communication_format = i2s_comm_format_t(I2S_COMM_FORMAT_STAND_I2S),.intr_alloc_flags = 0, // default interrupt priority.dma_buf_count = 8,.dma_buf_len = 1024,.use_apll = false};esp_err_t err = i2s_driver_install(I2S_PORT_0, &i2s_config, 0, NULL);if (err != ESP_OK){Serial.printf("I2S driver install failed (I2S_PORT_0): %d\n", err);while (true);}else{Serial.printf("I2S driver install OK\r\n");}
}其中，与缓存有关的包括下面的结构体成员和 i2s_driver_install() 函数：
.dma_buf_count = 8,.dma_buf_len = 1024,int dma_buf_count; /**< The total number of DMA buffers to receive/transmit data.* A descriptor includes some information such as buffer address,* the address of the next descriptor, and the buffer length.* Since one descriptor points to one buffer, therefore, 'dma_desc_num' can be interpreted as the total number of DMA buffers used to store data from DMA interrupt.* Notice that these buffers are internal to'i2s_read' and descriptors are created automatically inside of the I2S driver.* Users only need to set the buffer number while the length is derived from the parameter described below.*/int dma_buf_len; /**< Number of frames in a DMA buffer.* A frame means the data of all channels in a WS cycle.* The real_dma_buf_size = dma_buf_len * chan_num * bits_per_chan / 8.* For example, if two channels in stereo mode (i.e., 'channel_format' is set to 'I2S_CHANNEL_FMT_RIGHT_LEFT') are active,* and each channel transfers 32 bits (i.e., 'bits_per_sample' is set to 'I2S_BITS_PER_CHAN_32BIT'),* then the total number of bytes of a frame is 'channel_format' * 'bits_per_sample' = 2 * 32 / 8 = 8 bytes.* We assume that the current 'dma_buf_len' is 100, then the real length of the DMA buffer is 8 * 100 = 800 bytes.* Note that the length of an internal real DMA buffer shouldn't be greater than 4092.*/从注释（Notice that these buffers are internal to'i2s_read）可以得到 , DMA功能的使用，指定即可，而不需要自己实现——内部会自动完成相关的配置。
i2s_driver_install() 函数定义如下
/*** @brief Install and start I2S driver.** @param i2s_num I2S port number** @param i2s_config I2S configurations - see i2s_config_t struct** @param queue_size I2S event queue size/depth.*i2s 队列尺寸 I2S事件队列尺寸* @param i2s_queue I2S event queue handle, if set NULL, driver will not use an event queue.* /*i2s 队列 I2S事件队列句柄* This function must be called before any I2S driver read/write operations.** @return* - ESP_OK Success* - ESP_ERR_INVALID_ARG Parameter error* - ESP_ERR_NO_MEM Out of memory* - ESP_ERR_INVALID_STATE Current I2S port is in use*/
esp_err_t i2s_driver_install(i2s_port_t i2s_num, const i2s_config_t *i2s_config, int queue_size, void *i2s_queue);实际代码中没有使用，暂时也不知道所谓的 I2S 时间是什么？（莫非可能自动检测VAD端点检测？）