ESP32 I2S CLK飄動問題

[rong.tsai]

請問ESP32 I2S CLK一般操作情況下，頻率會一直在變嗎?
目前我們再操作PDM麥克風的時候，我們量到clk是2.6~2.9MHz在變化

這是初始化設定的部分程式碼。

Code: Select all

//i2s number
#define I2S_NUM           (0)
//i2s sample rate
#define I2S_SAMPLE_RATE   (44100)
//i2s data bits
#define I2S_SAMPLE_BITS   (16)
//I2S read buffer length
#define I2S_READ_LEN      ((I2S_SAMPLE_BITS / 8) * 1024)
//I2S data format
#define I2S_FORMAT        (I2S_CHANNEL_FMT_ONLY_RIGHT)
//I2S channel number
#define I2S_CHANNEL_NUM   ((I2S_FORMAT < I2S_CHANNEL_FMT_ONLY_RIGHT) ? (2) : (1))

    i2s_config_t i2s_config = {
        .mode = I2S_MODE_MASTER | I2S_MODE_RX | I2S_MODE_PDM,
        .sample_rate =  I2S_SAMPLE_RATE,
        .bits_per_sample = I2S_SAMPLE_BITS,
        .communication_format = I2S_COMM_FORMAT_PCM,
        .channel_format = I2S_FORMAT,
        .dma_buf_count = 32,
        .dma_buf_len = 64,
        .use_apll = true,
        .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1
    };
    i2s_pin_config_t pin_config = {
        .bck_io_num = -1,
        .ws_io_num = 21,
        .data_out_num = -1,
        .data_in_num = 36
    };
    
    i2s_driver_install(I2S_NUM, &i2s_config, 0, NULL);
    i2s_set_pin(I2S_NUM, &pin_config);