Self-testing an audio codec

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GuitarPhil

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Hi all,

Is it possible to do a 'self-test' of an audio codec (specifically an AK4619) by connecting it's I2S SDO to it's own SDI and then feed in a suitable audio signal from my signal generator to the analog input and look at the analog audio out? This would help me to configure the chip's registers correctly before I connect it to my DSP chip.

Thanks :)

Phil.
 
If you did that there'd be nothing to generate the three I2S clocks and nothing would happen. You need an I2S master to provide all three of these.
 
MarkT said:
If you did that there'd be nothing to generate the three I2S clocks and nothing would happen. You need an I2S master to provide all three of these.
Click to expand...

Thanks Mark. The external DSP chip is the Master and it's already supplying the three clocks. I just want to check I have the AK4619 configured correctly before I bring the DSP and its programming into the mix!

Phil.
 
In that case I think it should work - there's no harm trying. I'd stick a DC-blocking caps on the audio analog inputs as per
the recommended circuit in section 10 of the datasheet.
I'd also add a 10k series resistor in series with the signal generator to avoid any over-voltage "accidents"... For a differential
input the -ve input's cap can simply go to ground if your generator is single ended.
 
Thanks again Mark. I have the DC-blocking caps on the analog inputs and outputs and I think I have configured the AK4619 inputs as single-ended.

Good shout on the 10k resistor!

At the moment with a sine wave 440Hz 350mVp-p input signal I'm getting a 440Hz square wave out. I may need to check various gain settings in the AK4619. It's a complex chip :cool:

Phil.
 
I guess the microphone capable inputs have something like an extra 40--50dB of gain available, perhaps by default.
 
MarkT said:
I guess the microphone capable inputs have something like an extra 40--50dB of gain available, perhaps by default.
Click to expand...

That could be Mark. The default gain is 0dB (relative to what level I don't know!). I have tried setting the mic gains as low as possible (-6dB) but the output is still basically a square wave.

I scoped the SDIN and SDOUT pins and I can see the data stream changing when I alter the frequency and/or amplitude of the input so something is working, just not sure where it's going wrong.

Anyway, thanks for your help and suggestions. I will report back if I can find a solution as others may be interested in using this codec.

Phil.
 
I found my mistake! I had missed the connection from VREFH to AVDD (+3.3V) so the internal reference voltage was wrong/missing, hence the square wave output :rolleyes:

It's now working as expected :eek:

Phil.
 
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