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?

[Tesla DeLorean · Accepted solution]

Posted on November 30, 2017 at 22:17

Check ST-LINK FW version, seem to recall V2J25 would hold device in reset absent USB

[Heaton.John]

Posted on November 30, 2017 at 22:41

Thanks Clive. I did see the previous post on this issue and checked. The board firmware is V2J28 so I was assuming it wasn't a problem on this version.... I just checked the actual voltage and the NRST pin is in fact high (3V) when powered from the USB but when I externally power the board and check NRST, the voltage is only 1.4V. So something is fishy here. Do you know of a version that works for this board? 

[Tesla DeLorean]

Posted on December 01, 2017 at 00:38

I think the V2J28 should be fine, haven't dug through the schematic on the board

[Heaton.John]

Posted on December 08, 2017 at 15:06

Just so others may know, there is still a bug in the ST-LINK firmware (DEC 2017) that holds the NRST pin low, so the STM32 can't run. The work around until ST gets it fixed is to use a jumper wire between NRST and 3.3V pins on the header, this allows the chip will run as normal. Another workaround is to power the chip via external 3.3V, which avoids the problem entirely. Of course, then the ST-LINK won't function.

[eBirdman]

Posted on May 31, 2018 at 04:42

Hi John,  Are you aware if this problem has been fixed by now?

[Heaton.John]

Posted on May 31, 2018 at 13:39

I don't know if its fixed or not. I posted the question directly to ST and they just ignored it. I laid out a PCB myself and powered it via 3.3V, so its not a problem. Good luck

[eBirdman]

Posted on May 31, 2018 at 14:57

Are you able to use ST-LINK in your PCB while running the downloaded firmware ?

[Heaton.John]

Posted on May 31, 2018 at 15:16

Yes it will. As I said in my original post, even the Nucleo-32 board will function properly with ST-LINK in debug with the standard firmware. Just use a voltmeter to check pin 3 of CN4, you will see that the ST-LINK is pulling the signal low (0V). So if you take a wire jumper between Pin3 of CN4 and Pin14, you will bring that signal high (3.3V). After that, the ST-LINK will function properly.

[MJean]

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.