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ADAU1701 Aux ADC Readback

Question asked by njt on Mar 14, 2013
Latest reply on Mar 14, 2013 by BrettG



I've got a system running in which a micro polls a readback cell in Sigma to read back the current level read on the Aux ADC. This is from an external microphone pre-amp and mic.


I'm currently generating a number of sine tones, and reading off the mic values a number of times per tone, so I can do some averaging within the micro (this will probably change to an rms block at some point).


The problem I'm having is that the aux adc starts returning a static value after a few reads. There's no set number of reads I can do before it starts reading the same value. The following screenshot indicates this better -




It can be seen that I can manage 9 reads of the aux adc readback block before it starts returning a repeated value. 9 is not set either, sometimes it's less, sometimes more. I've debugged the i2c bus with my scope as much as I can, and nothing is locking up, it's just returning exactly the same value from the DSP each time.


Are there any glaring things I'm doing wrong?