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Getting digital microphones to work on EVAL-ADAU1777Z ?

Question asked by HonestEffort on Feb 27, 2018
Latest reply on Mar 2, 2018 by HonestEffort

I am trying to get a digital microphone input to work on EVAL-ADAU1777Z.


I have successfully brought up examples using 4 analog input channels through the ADCs.


I have some digital PDM mems microphones (SPH0641LU4H-1, Knowles). They look similar to some of the obsolete Analog Devices digital microphones (ADMP521Z). I have made a small PCB to adapt a digital microphone to J6 or J6 sockets, following the Fig.51 schematic in the eval board user guide.I also referenced the obsolete Analog Devices EVAL-ADMP521Z user guide (which seems to have a socket and pinout matching the EVAL-ADAU1777Z).


This microphone board only has 1 mic and 1 channel, although most of the setups I have seen use two digital mic's sharing a data line with L and R using rising/falling edges of the clock or vice versa.


I have followed the instructions on page 12 of the UG-1055 EVAL-ADAU1777Z user guide.


1) Set the pin/pad control according to Fig. 34 (MP6 set as Clock Output)

2) Set the BCLK value according to Fig. 35

3) Set the decimator panel to Fig. 36 (according to digital mic 0/1 or 2/3)


I am unable to get any audio output following the EVAL-ADAU1777z user guide. Are there additional settings/jumpers that I need to place to connect the clock, data, and Vdd/GND to the microphone daughter board?


Are there any more settings in SigmaStudio that need to be made to get digital microphones working with this eval board?


On a scope, probing across J7  (after programming with SigmaStudio), I get:


pin 1 GND

pin 2 GND

pin 3     3.07186MHz clock

pin 4     3.07186MHz clock

pin 5 GND

pin 6 GND

pin 7 GND

pin 8 Vdd 3.3V

pin 9 GND

pin 10 GND

pin 11 Vdd

pin 12 Vdd