NUCLEO-F411RE will not work with External 3V3 Source.

[GPann.1]

• I am trying to evaluate the low-power capabilities of the STM32F411 using the Nucleo Dev Kit.
• I have used a simple code provided in STM SDK to toggle LED 2 at 1 second interval.

• LED will toggle when the board is powered by on-board USB, or 5V at VIN.
• As a starting point for 3V3 external supply, I am using this (Image - Datasheet Page 22-Table 9)

• At first I tried to de-solder the Solder Bridges as recommended, and apply a 3v3 at the VDD pins -> I get 3V3 at the MCU but the LEDs are not toggling.
• I tried to cut off the Board, and Apply 3V3 at Vdd pins -> No LED Toggle.
• After cutting the board and Applying 5V at VIN as I did earlier -> No LED Toggle.

I am open to any suggestions and recommendations.

Thanks,

Gurbir

[Tesla DeLorean]

What do you see, voltage wise, at the NRST pin, and those of the VCAP pin(s)

[KnarfB]

Check VDD at Jumper JP6. Check at the connector that BOOT0 is low and NRST high. You can re-connect the cut-off ST-LINK via PA13 PA14 and GND and check/debug/program your board via ST-LINK.

hth

KnarfB

[S.Ma]

Read and check the schematics. Nucleo should have a tap point for mcu current excluding the rest. Make sure stlink power line is decoupled.

[GPann.1]

Hey Tesla,

- Voltage at NRST Pin = VDD(3.23V)

- Voltage at VCAP(C26) = 1.10V

- VCAP C25,C22 is DNP by Default. It is 0V at these Cap +ve Pads.

Thanks,Gurbir

[GPann.1]

Hi KnarfB.

- VDD at Jumper JC6 is 3V3 (SB2 is Desoldered to isolate the LDO)

- BOOT0/R33 is 0V and Connected to GND. NRST is HIGH.

- The Board works as expected when its powered by 5V VIN, E5V or STLINK. As soon as its changed to 3V3 it stops working.

I would also like to mention that my colleague was able to independently verify this 3V3 issue. I believe he received the dev kit from the same production batch. He was not able to get anything of 3V3 working.

Thanks, Gurbir

[GPann.1]

Hey,

I have isolated the MCU from ST-Link by Solder bridges and cutting the top part off. The LDO is also Isolated, I am still not able to get it working with 3v3. Thanks