Bootloader Limitations; Audio; Digital Microphones; Table 10. Digital Microphone-Related Jumper Settings - ST STM32L476ZG User Manual

UM1855
6.6.2

Bootloader limitations

Boot from the system flash memory results in executing bootloader code stored in the
system flash memory protected against write and erase. This allows in-system
programming (ISP), that is, flashing the MCU user flash memory. It also allows writing data
into RAM. The data come in via one of the communication interfaces.
The bootloader version can be identified by reading the bootloader ID at the address
0x1FFF6FFE.
All information about the device bootloader is described in the application note "STM32
microcontroller system memory boot mode" (AN2606) available at the
Refer to this document and follow the description of the bootloader versions and limitations.
6.7

Audio

A codec connected to the SAI interface of STM32L476ZG supports the TDM feature of the
SAI port. TDM feature offers STM32L476ZG the capability to stream two independent
stereo audio channels to two separate stereo analog audio outputs, simultaneously.
There are two digital microphones on the STM32L476G-EVAL board.
6.7.1

Digital microphones

U35 and U36 on the STM32L476G-EVAL board are 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 STM32L476ZG terminals, thanks to the integrated input digital filters. The
microphones are supplied with a programmable clock generated directly by STM32L476ZG.
As an option, the microphones can be connected to an audio codec device (U29). In this
configuration, U29 also supplies the PDM clock to the microphones.
Regardless of where the microphones are routed to, STM32L476ZG or audio codec device,
they can be power-supplied from either the VDD or MICBIAS1 output of the codec device.
Table 10
board.
Jumper
JP14
shows the settings of all jumpers associated with the digital microphones on the

Table 10. Digital microphone-related jumper settings

Setting
JP14
Default setting.
PDM clock for digital microphones comes from STM32L476ZG
JP14
PDM clock for digital microphones comes from the audio codec.
Configuration
UM1855 Rev 6
Hardware layout and configuration
www.st.com website.
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