ADAU1466 digital microphone connection setup

For our new design I need to use 4 PDM microphones with ADAU1466WBCPZ300 DSP.

Unfortunately, I can’t get any signal from mics on the OUT1 (I2S).

In my initial project all 4 mics mixed in to one left channel and internal tone generator routed to the right channel (see attached project).

I have audio on the right and no audio on the left channel.

What am I missing in the digital microphone’s setup?

Thank you.IN_OUT.zip

  • 0
    •  Analog Employees 
    on Dec 2, 2020 9:20 PM 1 month ago

    There are a few steps to configuring the DSP to use PDM mic inputs. Begin by specifying which pins you are using for the hardware interface. PDM mics typically have pins for CLK and DATA and each data input carries two channels. In your code, MP6 (pin 45) and MP7 (pin 46) are used as the two data inputs. Each of the two inputs use BCLK_OUT0 (pin 40) as the clock source.

        

    I’m assuming that you are running the microphones at 48 kHz since that is how they are shown in your project and you are not using an ASRC. The configuration below shows how the serial port would be set up to generate a bit clock of 3.072 MHz (48k x 32 x 2). OUT0 is shown consistent with the setup above. Under SERIAL_PORTS > Serial Outputs:

        

    The data input pins need to be configured, as well. Specifically, the multipurpose pins must be configured as PDM inputs rather than the default of GPIO, and the pins must be designated as using the MPx function. Slave select channel is ignored here, and debounce is not likely necessary. On the MULTIPURPOSE tab:

        

    With the register configuration done, you can proceed to use the PDM mic input block from the schematic as you have correctly done.