1.
If more than 300 mA current is needed by the board, the PC may be damaged or current supplied is limited
by the PC. As a consequence the board is not powered correctly.
2.
300 mA is requested at enumeration (since SB1 must be OFF), so the risk exists that the request is rejected
and the enumeration does not succeed if the the PC cannot provide such current. Consequently the board is
not power supplied (LED LD2 remains off).
+3V3 power supply
Using the +3V3 (CN4 pin 14) directly as power input is interesting, for instance if the 3.3 V is provided by a shield
board. In this case, the ST-LINK is not powered, thus programming and debugging features are not available.
When the board is powered by +3V3 (CN4 pin 14), solder bridges SB2 (NRST) and SB3 must be OFF.
6.4.3
External power supply output
When powered by USB or VIN, +5V (CN4 pin 4) can be used as output power supply for an Arduino
™
Nano
shield. In this case, the maximum current of the power source specified in
must be respected.
+3.3V (CN4 pin 14) is also a possible power supply output. The current is limited by the maximum current
capability of the regulator U3 (500 mA max).
6.5
Board functions
6.5.1
LEDs
LD1 ST-LINK COM LED
The bicolor LED LD1 (green, red) provides information about ST-LINK communication status. LD1 default color is
red. LD1 turns to green to indicate that communication is in progress between the PC and the ST-LINK, with the
following setup:
•
Blinking red: the first USB enumeration with the PC is taking place
•
Red on: the initialization between the PC and ST-LINK is complete
•
Blinking red or green: programming and debugging with target
•
Green on: communication finished and successful
•
Orange on: communication failure
LD2 PWR
The red LED indicates that the STM32G0 part is powered and 5 V power is available on CN4 pin 4.
LD3 USER
The LD3 USER green LED is connected to the following STM32G031K8T6 I/O:
•
PB3, if the configuration is SB12 ON, and SB13 OFF
•
PC6, if the configuration is SB12 OFF, and SB13 ON (default configuration)
It is also connected to the Arduino
™
D13 signal when SB12 is ON. To light this LED, a high-logic state “1” must be
written in the corresponding GPIO PB3 or PC6. A transistor drives the LED, therefore its consumption does not
affect the STM32G0 power measurement.
LD4 USB power fault (OC, overcurrent)
The LD4 red LED indicates that the board power consumption on USB ST-LINK exceeds 500 mA. Therefore, the
user must check the root cause of the overconsumption, and consequently power the STM32G0 Nucleo-32 board
with an external power supply if needed.
6.5.2
Push-button
B1 RESET/USER
This push-button is connected to NRST (PF2-NRST) and is used to reset the STM32G0 microcontroller or to
generate a USER event.
UM2591
Board functions
UM2591
-
Rev 1
page 13/26
