How to fix STM32WB55RG board no longer running code after attempting to power board through VBAT pin

IGaul.1 · ‎2022-07-07

Hi,

So for a project I'm working on I'm using an STM32WB55RG nucleo board. For my tests I've powered the board fine before using either usb port and through the VBAT pin when using a DC power supply. An aspect of my project is that it needs to be battery powered so I ran a 9V battery through a voltage divider to ~3.4V and sent it into the VBAT pin. Now LED 5 lights up showing it's being powered but LEDs 1-3 aren't lighting up as they would if the board ran my program. To debug I connected it via ST-Link to my computer but now it refuses to run the debug stating "no device found on target". I'm thinking I somehow screwed the pooch on this board and am wondering if it's savable?

I suspect it has something to do with the current but I can say that after measuring it it used about 30 mA and I figured it would have trouble at ~100 mA.

Side note: I'm now aware of just connecting the 9V directly into the VIN arduino port and I have my program running fine on a separate board powered that way.

Remy ISSALYS · ‎2022-07-19

Hello,

The VBAT pin allows to power the device VBAT domain (RTC, LSE and Backup registers) from an external battery, an external supercapacitor, or from VDD when no external battery nor an external supercapacitor are present. Three anti-tamper detection pins are available in VBAT mode. VBAT operation is automatically activated when VDD is not present. An internal VBAT battery charging circuit is embedded and can be activated when VDD is present.

In order to try to connect the board using ST LINK, check if all jumpers are correctly configured :

set correctly the jumper JP1 ([7-8] on USB STL).
JP2 is ON
JP3 is ON

Best Regards

IGaul.1 · ‎2022-07-22

Thank you for the reply! All jumper's are configured correctly. I realized I had 9V that powered the op amp parallel to a system for a GPIO pin. I think the 9V may have fried that pin and screwed the chip.