EVAL - ADAU1466Z throughput latency
Hi
I've just started using the ADAU1466Z eval board as part of an ANC project. I've got some NLMS and FxNLMS schematics working just fine, but...
When it comes to modelling the secondary transfer function of my physical speaker/error mic system, the FIR coefficients weren't coming out as expected. Seemed to be a longer transfer function than I had calculated.
I traced it back to the end-to-end throughput latency of the eval board - from analogue input to analogue output shows 1.3ms on my scope. This seems like a lot and is too much for my ANC application...
Does anyone else have experience with this board?
Are there settings I've missed (or other ways routing an analogue signal in and out of the board) to get the throughout latency down to a few clock cycles?
Or do I need to move away from a eval board? One of the stated applications of the 1466 is ANC, so it must be something I've missed...
Thank you in advance,
Richard
pipeline latency
anc projects
Hello Richard,
Your latency measurement is correct. Most of this delay, about 1.0 mS, stems from the oversampling digital antialiasing and reconstruction filters in the AD1938 Codec on the eval board -- see page 6 of its data sheet. These delays drop substantially at a 96K or 192K sample rate -- but unfortunately, the eval board hardwires the codec for 48K. I could not find any reference to ANC in the ADAU1466 data sheet. The ADAU1772 and -1777 are recommended for noise cancelling with feedback mics, as in noise-cancelling headphones. They have nowhere near the processing power of the Sigma 350 chips, but they feature built-in converters with near-zero latency.
Best regards,
Bob
Hi Bob
Really appreciate the feedback. I looks like I need to change to the chip
family you've pointed me to!
Thank you again
Richard
On Fri, 6 Jul 2018, 03:01 KJBob, <analog@analog-vm.hosted.jivesoftware.com>
Hi Richard,
Oh, sorry, I noticed your -1466 designs include NLMS filters. The chips I mentioned, though having low latency, do not have these. You could drop for example a ADAU1777 into a new design, open its toolbox and see if it can do what you need. Another possibility is to mate a low-latency codec with the -1466 DSP. For example, Cirrus Logic's CS4272 features roughly half the latency of the AD1938, but this still may not be fast enough. Besides you would need to build hardware to develop your application.
Best regards,
Bob
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