请问STA321MP输出的奇怪噪音来自哪里？

嗨，潘，

对于STA321MP，您可以控制输出通道的音量，请使用-80dB静音输出，然后再次检查输出噪音。

或者您可以断开麦克风PDM输出数据信号线，然后再次检查输出。

谢谢
YT



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hi Phan,

for STA321MP , you are able to control volume of output channel , please use -80dB to mute output , then check the output noise again.

or you can disconnect microphone PDM output data signal line , then check the output again.

Thanks
YT

嗨，

感谢聪明的建议！

我做同样的事情，噪音很清楚。



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Hi,

Thank for the clever suggestion!

I do the same and the noise is showed clearly.

嗨Phan，

你能告诉我STA321MP之后的信号路径吗？
你把I2S输出发送到DAC了吗？
如果是，请告诉我你的系统和I2S总线的时钟安排。

谢谢 ，
YT



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Hi Phan,

Could you let me know the signal path after STA321MP ?
did you send I2S output to a DAC ?
if yes, please let me know your clock arrangement for system and I2S bus .

Thanks ,
YT

嗨陶，


我正在使用STM32F7-DISCO板通过I2Sx和SPIx通道从STA321MP读取SDOxx。读取数据通过SAI流式传输到编解码器芯片组WM8994，以播放音频信号。 I2S / SPI总线的时钟约为1.025Mhz（16Khz * 32bit * 2音频通道）。

XTI的时钟由外部振荡器12.288 Mhz提供。
我当前的电路是否会产生噪音？我看到它与电源线信号（50hz）相关
我正在建造自己的电路板，我希望不会发生这种噪音。



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Hi Tao,


I am using STM32F7-DISCO board to read SDOxx from STA321MP via I2Sx and SPIx channels. The reading data is streamed to codec chipset WM8994 via SAI to play-out the audio signal. The clock for I2S/SPI bus is ~1.025Mhz (16Khz*32bit*2 audio channels).

The clock for XTI is supplied from external oscillator 12.288 Mhz.
Is the noise caused by my current circuit? I see It correlates with power line signal(50hz)
I am building my own board, I hope that kind of noise will not occur.

嗨Phan，

它看起来不像交流电源的50赫兹噪音，而是一些数字噪音，如爆米花。
根据您的描述，STA321MP的MCLK是由外部时钟源提供的，频率为12.288Mhz，您是否也将此osc用于STM32？由于STA321MP是从设备，I2S时钟（LRCK和BICK）应该由STM32（作为主设备）提供，如果MCLK与I2S时钟不同步，则会导致音频频段出现爆米花噪声。

谢谢 ，
YT



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Hi Phan,

it doesn't look like 50 hz noise from AC power supply , but some digital noise , like pop corn.
according to your discription, the MCLK for STA321MP had been provided from external clock source and freq is 12.288Mhz , did you also use this osc for STM32 ? due to STA321MP was a slave device, the I2S clock ( LRCK and BICK) should be provided from STM32 ( as master ), if MCLK was not synchronized with I2S clock , it will lead to pop corn noise in audio band .

Thanks ,
YT

感谢您的评论！我明白了你的观点。


STM32正在使用25Mhz osc。它们现在不是同一个时钟。我上次尝试从STM32向STA321MP提供MCLK。但由于某些原因，它上次没有用。现在，我将恢复该选项并检查，但我不认为这是根本原因。因为当我移除麦克风或为STA321MP的输出设置MUTE时，我得到相同的噪声信号。据我所知，即使时钟不同步，所有音频信号为0都可以无噪音地工作。如果我错了，请纠正。



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Thank for the comments! I got your point.


STM32 is using 25Mhz osc. They are not the same clock now. I tried to provide MCLK to STA321MP from STM32 last time. But for some reasons, it didn't work last time. Now, I will revert to that option and check but I don't think it is the root cause. Since when I removed Microphones or set MUTE for STA321MP's output, I get same noise signal. As far as my understanding, all audio signal is 0 would work without noise even the clock is not synchronize. Please correct if I am wrong.