Can an external microphone be connected to the STEVAL-BCN002V1?

[BShal.1]

Using the pins on the underside that normally dock into the development board, to connect an external mic to the pins in order to get better recording?

[Eleon BORLINI]

Hi @BShal.1​ ,

it is not so plug-and-play, I'm afraid. The mounted microphone on the STEVAL-BCN002V1 is connected to the BLUENRG-2 module, and to to the STM32. You might think to unsolder it and wire your own microphone, but it must have aa PDM interface as the onw soldered on the STEVAL board.

You might use other platforms more versatile, such as the X-NUCLEO-CCA02M2, for this purpose.

-Eleon

[BShal.1]

eleon, thank you for your insights... the problem with the x-nucleo is that it doesn't have the form factor of the round size that we need with the STEVAL-BCN002V1

if were to do the hack of de-soldering the microphone, then as long as the external mic had PDM interface, it could be done?

-brandon

[BShal.1]

in doing a search on MEMS microphone https://www.st.com/content/st_com/en/search.html#q=MEMS%20microphone-t=products-page=1

there are several options that come back.. i haven't dived into figure out if PDM interface is listed, but would this be possible using one of these?

[BShal.1]

i did find this doc: https://www.st.com/content/ccc/resource/technical/document/application_note/group0/7d/62/3d/ad/24/57/47/78/DM00380469/files/DM00380469.pdf/jcr:content/translations/en.DM00380469.pdf. page 15 shows list of PDM output MEMs microphones

[BShal.1]

then on page16 it talks about connecting a microphone to the STM32

[Eleon BORLINI]

Hi @BShal.1​ ,

yes, you can , but there is no STM32 on the round daughterboard of the STEVAL-BCN002V1. You can find it on the "motherboard".

By the way yes, you can solder another microphone, but shall be digital and top port (so, basically the part names containing a "T" in this list).

The digital microphone listed are all PDM: they are all the ones containing aa "D" in the part name, but bottom port mics have a different pad layout.

-Eleon

[BShal.1]

i have my experiences with arduino, so i am getting up to speed on this STEVAL-BCN002V1 platform. in our testing, we are only using the disc.. the docking part (motherboards where the STM32 is attached), where the micro USB is on, is used just for flashing.

given the disc plugs into the "motherboard" via the 10 pin connection, instead of trying to solder directly onto the chip (by removing the current MEMs microphone and then running an external one with wires to solder back in), that we could instead just connect the microphone (even the same one that was removed) with wires to the underside male pinouts ?

our issue is the microphone on the chip is inside a case and doesn't allow for clear audio recordings.

one idea is to mount the current MEMs mic in a way that the top port had exposure to the outside

we connect to the chip via bluetooth to pull off the sensor data

i do appreciate your time in helping to answer this. I am not an EE, and will get an EE to help with the execution of this experiment. I wanted to first check with the community about feasibility first.

-brandon

[BShal.1]

in other words, connecting to the 10 male pinouts on the bottom of the daughter card to add another microphone, as if we connected daughterboard to motherboard, and then ran wires of the mic to the motherboard

or, we de-solder the microphone and re-attach it with wires

[Eleon BORLINI]

Hi @BShal.1​ ,

The 10 pin connector has the following pinout:For a MEMS microphone, you need:

• Vdd (OK)
• GND (OK)
• L/R (GND or VDD, OK)
• PDM CLOCK
• PDM DATAOUT

You might think to manage the 2.4MHz CLOCK and DAATA with the UART, but I'm afraid it is not so straightforward... indeed, I'm not even 100%sure it is possible, I'm not so expert about the STM32L1 on the "motherboard". Usually, SPI or dedicated I2S are used for acquiring PDM microphones.

-Eleon