ADC on ADAU1701 not working
Hi All, I have a project running an ADAU1701 that does not want to work correctly. The ADAU runs on a 22.5MHz clock originating from a DIR9001. Fs is set at 44.1kHz with the program length on 1x (1024), both of the PLL's are pulled high for MCLK= fs x512. The I2S input works fine, and so are all the filters. However, the analog input and all of the GPIO inputs are not working correctly and can be seen jumping up and down with a level detector in sigma studio.
Strangely if I set the program length to 2x (512) analog input and GPIO's work fine, though the analog now has a noise-floor of -30dB. But filters are now messed up, a 2k -6db notch moves towards 3.5k for example. As far as I have understood from the ADAU datasheet, for a 44.1kHz sample rate the program length should be 1x (1024), is there a setting I am missing?
Schematic digital part:
Schematic analog part:
Registry settings in sigma studio:
Screencapture of Sigma Studio:
Hello Dikkie,
First lets start with the master clock. 22.5MHz / 44100 = 510.2040816326531
It must be EXACTLY 512 x fs. If it is not then the converters will be muted. Also, when you send clocks to the serial port as a slave, the clocks must also be derived and divided from the same master clock. This is an older part and the digital implementation is somewhat primitive.
So let's start there to get this sorted out.
Dave T
Hi Dave,
The DIR9001 is connected to a 22.5792MHz oscillator that is fully passed on to the adau, sorry for the confusion there.
Thank you for a swift reply :),
Dikkie
Hi Dave,
It turned out the clock was part of the problem. Both the Dir9001 and the ADAU were running off the same reset signal. Resulting in a lack of a clock for the ADAU on some startup conditions.
All is solved now, thank you for your time
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