Simultaneous serial audio and digital microphones on ADAU1777?
From the data sheet for the ADAU1777, it is clear that the input path can accept analog microphones, digital microphones, and serial audio inputs. I have successfully brought up designs on the EVAL-ADAU1777 that use mixed analog and digital PDM mic inputs, such as 2 analog and 2 digital PDM.
My question is, can the ADAU1777 simultaneously accept both digital PDM mic inputs AND serial audio inputs?
DAC_SDATA (the serial input pin) is only shared as a multipurpose pin MP0. I see where the serial data output ADC_SDATA0 cannot be used simultaneously with PDMOUT, and that serial data output ADC_SDATA1 shares a pin with CLKOUT, needed for digital microphones.
Can the serial data inputs be used simultaneously with, say, 2 digital microphones? I see that the "core input selection" block has 6 inputs and 4 outputs into the audio processing core, so I doubt that serial audio data inputs can be processed simultaneously to 4 digital microphones (6 channels total).
Anyone with experience in this area?
adau1772
Integrated/Special Purpose A/D Converters
adau1777
serial audio input
Audio CODECs
Hello HonestEffort,
The core only has four input channels. Yes, the input MUX has six choices, the four ADCs and the two channels coming in on the serial input port. So you can choose any combination of these input up to four.
Now, the digital mics, they use the decimators that are also used by the ADCs. Those decimators are setup for stereo sources. The digital mics are also setup for stereo (two) mics, one on each edge of the clock. So there are four channels of decimation. You can use all four for the ADCs or all four for digital mics or you can split them by two. Two for the ADCs and two for the digital mics.
Note on the SigmaStudio roting GUI they label the core input selections as Ain0/Dmic0, Ain1/Dmic1, etc. Because either the decimator is being used for the ADCs or for the Digital mics but not both.
So you certainly could use two digital mics and two channels from the serial port.
You also could use two digital mics, one ADC input channel and one serial port input channel. That would work. It all has to add up to four inputs.
Dave T
Thanks for the answer - slight follow-up question:
1) Can a serial audio input be routed directly to a DAC without ever going into the DSP core (and without, therefore, using one of the four DSP i/o paths)?
Hello HonestEffort,
Yes, you can route from the serial port directly to the DACs. You can also route the serial input port directly to the serial output port. This would be for when you daisy chain the parts and want to pass data through.
In SigmaStudio, The register control tab has the signal routing sub-tab that shows all this quite well.
Dave T
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