1 year, 7 months ago.
Nucleo-F303K8 fails to start program when supplied 5V on +5V pin but work when fed into VIN
I have a program that blinks the green LED it starts and runs fine when the board is ran from USB. It also runs fine when I feed voltage into the VIN pin while disconnected from the USB. When the 5V is delivered to the +5V pin while disconnected from the USB it fails to start the program or at least it fails to blink the LED indicating the program is running. SB1 is disconnected.
Anybody know how to adjust the jumpers / solder bridges so this works correctly?
I also need the configuration for supplying +3.3 to the +3V3 pin (CN4 pin 14) as the only power source. I already tried the configuration of removing sb9 and SB14 described on page 17 (6.2.2) of the users guide http://www.st.com/st-web-ui/static/active/en/resource/technical/document/user_manual/DM00231744.pdf
I did not have the same problem on Nucleo-401RE board which seems to be perfectly happy running from 3.3V or 5V.
Question relating to:
1 year, 6 months ago.
I have been working the same general problem. I want to be able to power the Nucleo-32 board via USB for development and testing, but use a separate 3.3V supply during normal operation. I think I have both a solution and an explanation of the behavior you have been seeing.
The +5V pin is normally used as an output, but you are correct that the +5V pin should also be usable as an input. This is subject to the constraints described in Section 6.2.2 of the User Manual (UM1956). One of those constraints is that SB9 (the NRST solder bridge) has to be OFF when power is brought in through the +5V pin. I suspect that SB9 was in its default ON configuration when you ran the test of powering the VIN pin vs. the +5V pin. This could have been your problem.
Note that the VIN pin drives the on-board 5V regulator U6, whose output is the regulated voltage E5V. E5V powers the 3.3V regulators U3 and U4 for the target MCU and the ST-Link MCU, respectively. The +5V pin only powers the target MCU regulator U3. This difference prevents the ST-LINK MCU from powering up when power is only applied to the +5V pin. As a result, the target MCU is held in the RESET condition if power is only applied to the +5V pin and SB9 is ON. This explains why your setup worked when powered through the VIN pin but not when powered through the +5V pin.
I do not have a Nucleo-32 board right now, but my planned solution is to configure SB9 = OFF (default SB9 = ON), remove jumper JP1 (on the back side of the board) and bring in the external 3.3V power supply through the VDD side of the two JP1 jumper pins. SB9 is the NRST solder bridge and must be OFF for this to work, as described above. This configuration is similar to what you have successfully used on your Nucleo-401RE board. You can go back and forth between the default and modified functionality by re-installing JP1. The only downside is that the target MCU is no longer automatically reset by the ST-LINK after a firmware update - you have to manually reset the target MCU using the RESET button on the Nucleo-32 board or by cycling the external 3.3V power supply.
1 year, 7 months ago.
+5V is an output. The board should be supplied by Vin or USB.
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