ADAU1701 -- I2S source without MCLK
As I understand from the datasheet (for the ADA1701 mini evaluation board), when reading audio from an I²S source, I need to connect the MCLK (approx. 12MHz) to the ADAU1701 input.
Is there a way around this? I'm trying to use the Tinysine AudioB I2S bluetooth-to-I2S device, and that one does not output a MCLK signal --- I haven't connected it yet, but I guess it outputs the 48kHz LRCLK and a 3.072MHz BCLK.
Any recommendations?
Thanks,
Carlos
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Audio Signal Processors
i2s input
source clock
SigmaDSP Audio Processors
adau1701
Hello Carlos,
Setup the PLL Mode pins for 64x fs operation and you will be able to use the bit clock as an MCLK signal. The only detail is that the part will not initialize until it sees master clock and so you have to account for that in your system. I think if you selfboot it will simply wait until it sees a master clock, then it will initialize and boot up. If you have a controller booting it up then it has to wait until the DSP is initialized and then program the part.
The other detail is that the master clock signal should not stop and start and should not suddenly change frequency like when the I2S signal changes from 44.1Khz to 48kHz. You might run into issues.
Dave T
Thanks Dave,
One big "d'oh!" moment on my side: I see now that this information is in Table 12 in the datasheet! Thanks for pointing it out !!
Follow-up question: you point out the issue of the PLL being affected by the source changing between 44.1kHz and 48kHz. Is this something that other parts solve? (e.g., the ADAU1452 or other models that have rate converters and multiple clock domains?)
Thanks,
Carlos
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Hello Carlos,
LOL, I have some of those Duh? moments as well! Glad to know you are human!
Yes, the 1452 family of products have sample rate converters and many clock generators so they can operate in several clock domains at the same time.
Dave T
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