有一个大概的猜测：
在不使用ADC/DAC时，全双工下，时钟信号是TX为master，RX为slave，TX和RX内部共享时钟信号，TX同时为RX和外部codec提供时钟信号，使得所有时钟同步
而在ADC/DAC模式下，TX和RX都是master，内部不共享时钟信号，导致时钟并不完全同步。

Dear shailesh.korat,

You asked really good questions! Actually some answers already on the way, you will see them in programming guide soon.

A1 : dma_buf_count : The total number of descriptors used by I2S DMA to receive/transmit data. A descriptor includes some information such as buffer address ...

Hi shailesh.korat,

Glad to see you!
For the first question, here is the explanation for overtime_tick:

Meaning
1. Generally speaking, 'overtime_tick' is the ticks that 'i2s_read' should cost, that means, if the i2s_read task wait for more than 'overtime_tick', there must be data dropped.
2 ...

mr_jing 您好，

对于您提到的频率不准确的问题，是由时钟源造成的。使用较高采样频率时，PLL160M的时钟分频精度较差，而APLL时钟源能够产生一个更精确的频率，但由于驱动中APLL分频系数计算方式的局限性，目前对于高采样频率的支持不够好，我们会尽快修复该问题，感谢您的反馈！

Ps: 当使用APLL时，其最高支持128MHz，而从APLL分频得到MCLK至少为2分频，即MCLK <= 64MHz，一般MCLK到BCLK也至少是2分频，所以此时BCLK <= 32MHz

mr_jing 您好，

非常感谢您的反馈，请问能否提供一下这些，以便定位具体问题：

1. IDF版本
2. 文档关于BCK最高能到40MHz表述的具体段落
3. 使用的逻辑分析仪采样频率

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从提供的代码中发现i2s_config_t中的mclk_multiple字段并未设置，默认为256，由于BCLK是由MCLK分频得到，而MCLK由APLL或PLL160M分频得到，想要获得较大的BCLK，就需要设置较小的MCLK分频系数以及BCLK分频系数，MCLK的分频系数是自适应的，没法改变 ...

Dear shailesh.korat,

Nice to hear your feedback! Seems you met another data lost problem, I need some time to test this issue, but recently I wrote a specific example for the data drop issue, you can have a try and hope it can help.

The key is to create at least two receive buffers, if one is ...

目前PDM的支持情况是：
ESP32：TX RX
ESP32S2：不支持
ESP32C3：TX
ESP32S3：TX RX

不支持，ESP32-C3仅支持PDM TX~

@shailesh.korat
Sorry for the late reply~
Thank you very much for your significant information! After some experiments, I think I find the reason of data clip (in other word, data lost).
Actually, received data buffer length is not really related to the dma_buf_len, but is related to the sample ...

Few days ago, a fix commit (a287f34f88e78759cf09d2d9018b49adb70ea6fd) for apll clock is updated to the github, you can have a try with both 'apll on' and 'apll off' condition on the latest master branch. If it still not working, I might need your register dump for debugging.