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aditya
aditya
Associate II
September 14, 2017
Question

Noise in headphone output

  • September 14, 2017
  • 1 reply
  • 2020 views
Posted on September 14, 2017 at 13:50

I'm using STM32f4-Discovery board for an audio application.

I'm using the onboard codec CS43L22, in analog passthrough mode. But I'm getting high frequency noise on the output over headphones.

Can anyone tell what could be the possible reason for this noise and what might be the solution?

#cs43l22 #audio-codec #stm32f4 #stm32f4discovery-audio-codec #discovery #adc-noise
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1 reply

Vangelis Fortounas
Vangelis Fortounas
Associate II
September 15, 2017
Posted on September 15, 2017 at 11:06

Hi.

You mean you have noise without some input signal ?

0690X00000608FmQAI.png0690X00000608G6QAI.png

Is the correct AnalogIN  input selected?

If for example you have selected the input from PDM_OUT, you hear the digital ''noise'' of microphone.

If you have selected the input from DAC_OUT...Make a test , configure the DAC_OUT   PA4 as GPIO  PP output in low state.  Observe for noise. If noise exists the CS43L22 is not correctly intialized or has some HW malfunction.

aditya
adityaAuthor
Associate II
September 15, 2017
Posted on September 15, 2017 at 11:25

Hi Vangelis,

Thank you for your reply.

I'm taking input from an external analog mic. The flow is Mic -> ADC -> DAC -> Codec

You mean you have noise without some input signal ?

-In the above flow, even if I don't give any input to ADC, there is some noise. (Some frequency components-4kHz, 4.5kHz, 16kHz).

Is the correct AnalogIN  input selected?

-Yes. I'm using AIN1A, AIN1B.

Selected input is DAC_OUT.

If noise exists the CS43L22 is not correctly initialized

- Can you help with initialization?

Thank You

Vangelis Fortounas
Vangelis Fortounas
Associate II
September 15, 2017
Posted on September 15, 2017 at 12:36

Hello again.

I can't help you  by giving you the correct sequence of register values must put in CS43L22( i don't have time to study the registers)

But in general  (with some study also)

Initialize I2C port to communicate with cs43l22  (PB9, PB6)

initialize PD4 pin as reset pin to cs43l22 (GPIO PP output)

Apply the reset sequence (by the  datasheet) after power on.

and  ...  begin to send via I2C, the commands to initialize the cs43l22.

0690X00000608GBQAY.png
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