ADAU1701 GPIO synced to sample rate

wygonski Question

May 12, 2015 00:00

I'm working with a ADAU1701 with an interface to a microcontroller and numerous other system components. The uC needs to do some processing with data generated by the SigmaDSP, and the processing should be done at a 1 kHz rate synchronized to the 48k DSP sample rate. So far, I can successfully interrupt the uC with a GP output from the SigmaDSP and read the data I need with a DSP Readback cell. The GP output from the DSP is generated by a stopwatch, however I am finding that it doesn't seem to be synchronized to the analog output. I observed this by triggering a scope on this pulse train while displaying the analog sine output (the analog out jitters/drifts with respect to the pulses).

Here's the graph. I was expecting that the GPIO_1 output pulse would be in sync with the DAC0 output signal.

Is there something I'm not understanding about this, or is there a better way to sync the GPIO with the sample rate?

Audio Signal Processors

SigmaDSP Audio Processors

adau1701

4769388f35991c0a0aa6f3af36d37811.png-620x408.png

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jon71 Reply

May 13, 2015 00:00

I think you have two issues: first, the counter starts at zero, second, you don't trigger a reset until the counter is greater than 48. So that counter is running from 0 to 49, which is causing the drift.

Also you want to consider that the DAC will have latency from the core (GPIO/SDOUT). Not sure if that is important for your application or not, but you can compensate with a delay on the GPIO.

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