Audio; Digital Microphones; Table 8. Digital Microphone-Related Jumper Settings - ST STM32L4R9I-EVAL User Manual

UM2248
WA1: add a delay between sending the Write command and its ACK request. Its duration
must be the duration of the 256-Byte Flash write time.
WA2: read back after each writing operation (256 bytes or at end of user code flashing) and
in case of error start writing again.
WA3: Using bootloader, load a patch code in RAM to write in Flash memory through the
same Write Memory write protocol as bootloader (code provided by ST).
6.9

Audio

A codec connected to the STM32L4R9AII6 SAI interface supports the DSAI port TDM
feature. This offers STM32L4R9AII6 the capability to simultaneously stream two
independent stereo audio channels to two separate stereo analog audio outputs.
There are two digital microphones on the STM32L4R9I-EVAL board.
6.9.1

Digital microphones

U30 and U31 on the STM32L4R9I-EVAL board are MP34DT01TR MEMS digital
omnidirectional microphones providing PDM (pulse density modulation) outputs. To share
the same data line, their outputs are interlaced. The combined data output of the
microphones is directly routed to STM32L4R9AII6 terminals, thanks to the integrated input
digital filters. The microphones are supplied with a programmable clock generated directly
by STM32L4R9AII6.
As an option, the microphones are connected to U26 WM8994, the Wolfson audio codec
device. In that configuration, U26 also supplies the PDM clock to the microphones.
Regardless of where the microphones are routed to, STM32L4R9AII6 or WM8994, their
power supplier is either VDD or MICBIAS1 output of the WM8994 codec device.
Table 8 shows the settings of all jumpers associated with the digital microphones on the
board.
Jumper
JP16
JP15

Table 8. Digital microphone-related jumper settings

Setting
The PDM clock for digital microphones comes from the WM8994
1 2 3
codec.
Default setting.
1 2 3
The PDM clock for digital microphones comes from
STM32L4R9AII6.
The power supply of digital microphones is generated by
1 2 3
WM8994 codec.
Default setting.
1 2 3
The power supply of digital microphones is V
UM2248 Rev 4
Hardware layout and configuration
Configuration
.
DD
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