STM32L432 Nucleo-32 External Power

[Heaton.John]

Posted on November 30, 2017 at 21:45

I have developed a program that runs on the STM32L432 Nucleo-32. When I write the program to the demo board using the USB everything works great. When I remove the USB cable and connect 5V/GND to the board, L2 goes red but the program doesn't run (I have the green LED flash). If I plug the USB cable in after powering up the board, the program does start to run. If I run the exact same program on my STM32476 Nucleo-64, the program runs fine (power jumper JP5 set to E5V). There is no mention of additional settings in the manual or datasheet for the STM32432. Any thoughts on this issue? What is the difference in powering the two demo boards?

[LGrub.2]

Hello, I had the same issue i.e.

when powering the stml432kc from the 5V pin only, the program would not start as the reset pin is low

• st-link version: v2j36m26
• sb9: connected

My solution:

• connect a 150Ohm resistor between RST and 3V3 (the outputs of the arduino nano header)
• that way, RST is pulled high as long as the ST-LINK chip is not powered on and the program starts.
• I tried it with 330Ohm and and 6.8k, but that did not work.

If anybody sees any issues with that solution, I'd be happy to know about it :)

[VNava.1]

Hello Community! Any news regarding this issue?

I have the same problem when I supply the NUCLEO F303K8 with +5V or +3V3. If I connect RST pin (CN4 pin3) to the +3V3 pin (CN4 pin14) I can se my project works (example: blinking LED3) but I don't know if from the hardware point of view this is a correct procedure.

For example, regarding this issue, @MJean​ said in this post

"With the jumper, even 5V or 3.3V, power consumption rise to 80mA !

I just remove jumper SB9 (between STLINK T_NRST and STM32L432 NRST) and both standalone run or STLINK debug run correctly."

Which is the correct solution?

• A jumper between RST and 3V3 (with or without 150 Ohm resistor)
• Removing SB9
• Other solution

Thank you in advance

Vincenzo

[JMarc.5]

Hello I've got the same issue when powering an F303Ze Nucleo with 5V(It works fine when the USB is connected but the code doesn't start when it's only with 5V).

Did you find a solution?

[VNava.1]

Hi! I considered valid the answer given by @MJean​. He said in this post:

"I just remove jumper SB9 (between STLINK T_NRST and STM32L432 NRST) and both standalone run or STLINK debug run correctly". Also the NUCLEO manual said:

 

You can consider also the possibility to put always high the value of the NRST pin connecting it with a 150 Ohm resistor, but I'm not sure about the correctness of this solution.

[FFUMI.1]

Hi all, I know it'a bit old, but I'm facing exactly the same problem here, with a L432KC Nucleo-32 board: when powered through the +5V (CN4 pin 4), the board won't boot up. Ok, I've seen a few suggestions here, to solve this problem:

1) close (on) SB9 jumper

2) short NRST (CN4 pin 3) with 3V3 (CN4 pin 14)

3) pull NRST up to 3.3V with a 150 Ohm resistor between RST and 3V3

Solution 1 is permanent and won't allow programming the board through USB, unless physically reverting the SP9 configuration. So, I would go for 2 or 3, but I'm not sure what is the correct one. Pulling with 150 Ohm is a rather strong pull, similar to a short I'd say, so I wonder if anyone has measured the overall current drain in such a configuration, and if it will make the USB programming still possible.

I still wonder why ST won't fix the User Manual, explaining that and providing a complete solution for an external power scheme. Is there an Errata around, by chance?