Hardware layout and configuration
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happen if the PC6 GPIO is controlled by the software of STM32L476ZGT6 such that, it
enables the output of U1 power switch.
2.8.2
STM32L476G-EVAL used as USB host
When a “USB device” connection to the CN1 Micro-AB USB connector is detected, the
STM32L476G-EVAL board starts behaving as “USB host”. It sources 5 V on the VBUS
terminal of CN1 Micro-AB USB connector to power the USB device. For this to happen, the
STM32L476ZGT6 MCU sets the U1 power switch STMPS2151STR to ON state. The LD5
green LED marked VBUS indicates that the peripheral is supplied from the board. The LD6
red LED marked FAULT lights up if over-current is detected. The JP19 jumper must be
closed to allow the PC6 GPIO to control the U1 power switch.
In any other STM32L476G-EVAL powering option, the JP19 jumper should be open, to
avoid accidental damage caused to an external USB host.
2.8.3 Configuration
elements
related with USB OTG FS port
The following STM32L476ZGT6 terminals related with USB OTG FS port control are shared
by other resources of the STM32L476G-EVAL board:
•
PB12, used as USB over-current input (USBOTG_OVRCR signal); it is shared with
SWP, touch sensing, LCD glass module and motor control resources
•
PB13, used as USB power ready input (USBOTG_PRDY signal); it is shared with NFC,
touch sensing and LCD glass module resources
•
PC6, used as USB power switch control (USBOTG_PPWR signal); it is shared with
touch sensing, LCD glass module and motor control
Configuration elements related with the USB OTG FS port, such as jumpers, solder bridges
and zero-ohm resistors, shunt the shared ports toward different resources or determine the
operating mode of the USB OTG FS port. By default, they are set such as to enable the
USB OTG FS port operation where STM32L476G-EVAL plays USB device role and can be
connected to a USB host.
Table 8
gives an overview of all configuration elements related
with the USB OTG FS port. The LCD glass module daughterboard should be connected in
I/O position.
USBOTG_OVRCR and USBOTG_PRDY signals, requiring the PB12 and PB13 ports of
STM32L476ZGT6, are only exploited when STM32L476G-EVAL acts as USB host. That is
why, the USB host function of STM32L476G-EVAL is exclusive with alternate functions also
requiring PB12 and PB13 ports of STM32L476ZGT6 - NFC, touch sensing, motor control,
SWP.
The PB12 and PB13 ports of STM32L476ZGT6 are not required for the USB OTG FS port
operating as USB device.
Table 8. Configuration elements related with USB OTG FS port
Element
Setting
Description
JP19
Open
USB OTG FS port can be connected with a USB
host
and get power
from it. If connected with USB device, STM32L476G-EVAL cannot
supply power to it.
Closed
Default setting.
USB OTG FS port can be connected with a USB device and supply
power to it. It must not be connected with USB host.
