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STM32F4DISC.: Using CS43L22 only with analog signals and without I2S?

Question asked by Chris on Oct 2, 2012
Hi!

I am trying to use the CS43L22 in a very simple way: only to amplify an analog signal created with the internal DACs of the STM32F4. On the Discovery board the output of DAC1 is routed to AINxx. So I create a 0-3V, 1000Hz saw tooth signal on PA4 (which I can measure).
I also did the CS43L22 initialization via I2C and checked that all registers are set properly by rereading them and showing them on an attached LCD. I enabled the analog inputs, the mixers and the volume control. So that all is fine.

In the CS43L22 data sheet I read about the init procedure and it says that I need a master clock on MCLK for the charge pumps of the internal amplifiers. So I use a timer to create a simple 7MHz rectangle singal for PC7 (which is routed to MCLK of the CS43L22).

But: There is no output at all.

I also tried to create beeps using the CS43L22 internal beep generator but I  get nothing out :-(

I also have read the initialization procedures in the Audio Codec example carefully and used this for my code - but I am not able to get anything out of the earphone connector.

When using the example alone, I can hear the repeating music file - so hardware should be ok.

So my question is: is it ok to only clock MCLK for a working chip? Or is it mandatory to have a I2S signal?

May I have overlooked something and I need more to get sound?

Thank you for *any *hints,
Chris

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