AnsweredAssumed Answered

ADAU1701 AUDIO ADC's Problem

Question asked by bill on Dec 27, 2012
Latest reply on Aug 13, 2014 by kaeroul

I have created a PCB with 2 ADAU1701's. Both are running as slaves. MCLKI is 24.576Mhz . I will not be using any pin as a serial Audio line. So I have no external BCLK or LRCLK to/from either device. All of my audio will be coming from or into the audio DAC's/ADC's.  Just for a test, DSP B  is feeding an internally generated differential audio signal out of DAC0 and DAC1 (see attached project file). This audio is sent to a differential amp network, added together and output as a single ended audio signal (see image of final signal measured at input of blocking capacitor into ADC1) . The signal ended audio signal is used as an input back into the audio ADC1of DSP B. The ADC_RES is 17.8k ohm, I have 47uF blocking capacitors inline with 18.2kohm resistors into ADC0 and ADC1.  I am feeding the input of ADC1 directly to the DAC3 output (see image of output signal measured before active filter). As you can see the sine wave is clipping and nothing I do will prevent this. I have tried changing the gain but Iose one half of the sine wave (see attached image). I'm sure it's something simple I'm missing but can't figure it out for the life of me. Any help would be appreciated. Do i have to have an external LRCLK and BCLK to run the audio ADC's. What could it be?