NUCLEO-N657X0-Q: Confliciting info on number of supported PDM MEMs microphones

[csaji]

Hello,

I have a STM32 NUCLEO-N657X0-Q development board. I wanted to interface with 8 digital PDM MEMs microphones. 

In section 68.2 of the STM32N6 reference manual, it states that the N6 supports a "PDM interface, supporting up to 4 microphone pairs". Also in section 2.2.3 of AN5027, it states that if 8 microphone want to be used, the recommended data IO lines are SAI_D1, SAI_D2, SAI_D3, and SAI_D4.

Using CubeMX, I see no option for microphone pair 7-8. In addition to this, SAI_D4 doesn't exist when I search for the pin. 

So how do I interface (if possible), the last microphone pair? 

Thanks,

Christopher

[KDJEM.1]

Hello @csaji and welcome to the community,

Thank you for bringing this issue to our attention.

I will report this issue internally for checking.

I will get back to you as soon as possible.

Internal ticket number CDM0061647(This is an internal tracking number and is not accessible or usable by customers).  

Thank you.

Kaouthar

[KDJEM.1 · Accepted solution]

Hello @csaji;

It is a typo, there are only three data IO: SAI_D1, SAI_D2, SAI_D3, in that case it will just support 3 pairs of microphones. Two microphones for each data line. So it supports actually 6 microphones.

Thank you.

Kaouthar

[Andrew Neil]

See also: Connecting 8 PDM microphones to STM32N6

TL; DR: Datasheet DS14791 (Rev 9), AN5027 (Rev 2), and RM0486 (Rev 3) all have the typo.