I2S-output not working as expected

QA40x
1

Hi,

I have just received my QA403 that I purchased primarily for testing some I2S automotive amplifier designs.

I did some preliminary tests and I have noticed a (to me) strange behavior of the I2S-output:

  • When I enable GEN1 and/or GEN2 that analog output signal has an envelope with a period of ~180ms, but the I2S-signal has a constant amplitude
  • With the mutlitone, white noise and freq respones generators I don’t get any I2S output.
  • When I run automated tests the I2S output is very unreliable. Most of the time I can make it work, by disabling and reenabling I2S via the button right before starting the test routine, but not always.
  • When an automated tests has finished, the I2S signal remains active, i.e. the latest waveform is put out indefinitely until I switch it off manually via the I2S-button.
  • E.g. for the “AMP frequency response chirp” test I could not get a I2S-signal at all

I am not sure if that is the intended behaviour. I would expect the I2S-Signal simple be an exact copy of the analog signal.

I am currently using QA40x V1.215

Any thought on that?

Best Regards
Matthias

2

Hi @Mattias, yes, this is the expected behavior. The I2S is currently completely independent of the DAC/ADC, meaning they could play completely separate streams. But coincident with the QA404 shipping at some point in the future, this will change and the DAC outputs will be the same on QA402/QA403/QA404. There will also be a MODE selection where you can pick continuous or bursted operation. Continuous means the DAC is constantly playing a sine, multitone, noise, etc. Bursted is operation like today. And then, you will have the ability to select the input source for analysis, which will be either I2S or ADC. But, as I said, this isn’t anytime soon. Certainly not this year.