Headphones Outputs; Limitations In Using Audio Features; Usb Otg Fs Port; Stm32L4R9I-Eval Used As A Usb Device - ST STM32L4R9I User Manual

UM2248
6.9.2

Headphones outputs

The STM32L4R9I-EVAL main board potentially drives two sets of stereo headphones.
Identical or different stereo audio contents are played back in each set of headphones.
STM32L4R9AII6 sends up to two independent stereo audio channels, via its SAI1 TDM port,
to the WM8994 codec device. The codec device converts the digital audio stream to stereo
analog signals. It then boosts them to drive directly headphones connecting to 3.5 mm stereo
jack receptacles on the main board, CN24 for Audio-output1, and CN23 for Audio_output2.
The audio jack (CN23) takes its signal from the WM8994 codec device output intended for
driving an amplifier for loudspeakers. A hardware adaptation is incorporated on the main
board to make it compatible with a direct headphone drive. The adaptation consists of
coupling capacitors blocking the DC component of the signal, attenuator, and antipop
resistors. Software in the Class-AB Linear mode and not in the Class-D Switching mode
must configure the loudspeaker output of the WM8994 codec device.
The I²C-bus address of WM8994 is 0b0011 010x.
6.9.3

Limitations in using audio features

Due to the share of some terminals of STM32L4R9AII6 by multiple peripherals, the following
limitations apply in using the audio features:
•
If the SAI1_MCLKA and SAI1_FSA are used as part of the SAI1 port, they cannot be
used as CAN peripherals.
• If the SAI1_SDB is used as part of the SAI1 port, it cannot be used as the Comp2_OUT
signal.
•
If the SAI1 port of STM32L4R9AII6 is used for streaming audio to the WM8994 codec
IC, STM32L4R9AII6 cannot control the motor.
•
If the digital microphones are attached to STM32L4R9AII6, control of the motor cannot
be driven.
6.10

USB OTG FS port

The STM32L4R9I-EVAL main board supports USB OTG full-speed (FS) communication.
The USB OTG connector (CN3) is of the Micro-AB type.
6.10.1

STM32L4R9I-EVAL used as a USB Device

When a USB Host connection to the Micro-AB USB connector (CN3) of STM32L4R9I-EVAL
is detected, the main board starts behaving like a USB Device. Depending on the powering
capability of the USB host, the main board potentially takes power from the V
CN3. In the main board schematic diagrams, the corresponding power voltage line is called
U5V.
Section 6.5
The resistor R23 must be left OFF to prevent STM32L4R9I-EVAL from sourcing the 5 V to the
V terminal, which would cause conflict with the 5 V sourced by the USB host. This might
BUS
happen if the software of the MFX MCU controls MFX_GPIO6 such that, it enables the output
of the power switch (U2).
provides information on how to set associated jumpers for this powering option.
UM2248 Rev 5
Hardware layout and configuration
terminal of
BUS
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