Sabre-SDB WM8962 GPIO5 default

[andrewdyer]

In reviewing the schematics for the Sabre-SDB and datasheet for the WM8962 codec (rev. 4.2, top of page 151), it says

Note that it is important that the GPIO5 input is held in a defined logic state (logic ‘0’ or logic ‘1’) during
start-up; it must not be left floating.

On the Sabre-SDB this pin appears to be floating in the default configuration (no digital microphones installed).  Is this intentional?  If I was to add a resistor to set the state, which is the preferred setting?

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[gusarambula]

On the SABRE schematics this pin is connected to an ADMP421B which is a microphone port so this pin is not floating but rather connected to this port. I would recommend looking at the characteristics of your microphone port, if you are using the same you may follow the SABRE board design.

[andrewdyer]

On the schematics I have (dated Feb 19, 2013) those parts are listed as DNP which I assume means 'Do Not Populate'.

[gusarambula]

Yes, DNP stands for Do Not Populate. However, the schematics I checked do not have this legend and are from the same date. My schematic is SCH-27392 Rev C3. The digital microphones WM7230 were replaced with ADMP421 on Rev B4 of the board so they should be there on the latest revisions.

[andrewdyer]

My schematic is SCH-27516 Rev. C3, so different part number.  It looks like there are different schematics available depending on whether you start from the SDB reference platform page or the SDB board page, and they are at different revisions.  Mine is the one from the SDB board page.  I assumed the two boards were the same and the reference platform board just included the display, case, etc.

So for the SDB board, where the parts are not stuffed my question still stands.  For the reference platform if the parts are stuffed, then the question is what are the digital microphone outputs doing during reset?  It wasn't really clear to me looking at the AMDP421 datasheet what happens then, but I admit I just skimmed it.

[art]

Q. Is this intentional?

A. No.

Q. If I was to add a resistor to set the state, which is the preferred setting?

A. The WM8962 Datasheet should better say that.

Have a great day,
Artur

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