6.6
Board functions
6.6.1
LEDs
LD1 STLINK-V3E COM LED
The bicolor LED LD1 (green, red) provides information about STLINK-V3E communication status. LD1 default
color is red. LD1 turns to green to indicate that communication is in progress between the PC and the STLINK-
V3E, with the following setup:
•
Blinking red: the first USB enumeration with the PC is taking place
•
Red on: when the initialization between the PC and STLINK-V3E is complete
•
Blinking red/green: during communication with target
•
Green on: communication finished and successful
•
Orange on: communication failure
LD2 USER
This green LED is a user LED connected to STM32G4 I/O PA5 (SB6 ON) corresponding to the Arduino
™
D13. To
light LED LD2, a high logic state “1” must be written in the corresponding GPIO PA5. A transistor is used to drive
the LED LD2. LD2 consumption does not impact the VDD STM32G4 power measurement, since LD2 is isolated
from it.
LD3 PWR
The green LED indicates that the STM32G4 part is powered and +5 V power is available on CN6 pin 5 and CN7
pin 18.
LD4 USB power fault (OC, overcurrent)
LD4 indicates that the board power consumption on USB ST-LINK exceeds 500 mA. Consequently, the user must
power the board using an external power supply.
6.6.2
Push-buttons
B1 USER (blue button)
The user button is connected to the STM32G4 I/O PC13 by default (Tamper support, SB16 ON and SB21 OFF) or
PA0 (Wakeup support, SB21 ON and SB16 OFF) of the STM32G4 microcontroller.
B2 RESET (black button)
This push-button is connected to NRST (PG10-NRST) and is used to RESET the STM32G4 microcontroller.
6.6.3
MCU voltage selection on VREF+
The STM32G4 Nucleo-64 board offers the possibility to supply the STM32G4 microcontroller with either VREF or
VDD on its VREF+ input voltage pin.
VREF+ is targeted to offer high-end analog device, especially for precise analog applications (ADC converters
usage) with the STM32G4 microcontroller.
In the STM32G4 Nucleo-64 board, the VREF+ can be supplied with a very stable output voltage provided by the
TL1431CL5T. The TL1431CL5T is an adjustable shunt voltage reference with guaranteed temperature stability
over the entire operating temperature range. The output voltage may be set to any value between 2.5 V and up to
36 V with two external resistors. The TL1431CL5T operates with a wide current range from 1 mA to 100 mA with
a typical dynamic impedance of 0.2 Ω.
JP8 jumper is used to select either the VREF or VDD voltage for VREF+.
•
Place the JP8 jumper on [1-2] to supply the MCU VREF+ with VREF
–
To have VREF at 2.5 V, then SB14 is fitted and R34 is not fitted
–
To have VREF at 3.25 V, then SB14 is not fitted. VREF = 2,5 × (1 + (R33 / R34)) =
2,5 × (1 + (10k / 33k)).
UM2505
Board functions
UM2505
-
Rev 2
page 23/43
