Did I break my Nucleo-C092RC ?

MaxiTaxi11 · ‎2026-04-25

Hello everyone

i am currently working on a project with a NUCLEO-C092RC Board. With this Board i want to send OBD-II Frames to my car and receive reponses with data. I also use a LCD Display via SPI. But now i have a problem. i connected CANH/L with the Board. I also connected 12V and GND from the OBD-II-Port to a buck converter, which steps the voltage down to 7 V for VIN on the Board, which should be within spec. Then i tried to send a frame, but i did not get a response, when the Board was only powered by 12V via buck converter. After that i think i broke my MCU, because then i connected my PC with the Board and switched the power source back from VIN to ST-Link with a jumper. I was able to debug my programm. but when i also disconnected CANL and CANH from the Board or switching the jumper from VIN to ST-Link (i am nor sure anymore), the red LED from STMPS2141STR came on. It only turns off, if i disconnect VDD from 3V3 Volt with pulling JP5. I also measured from what i think is the VDD header pin of JP5 to GND what showed 2 ohms....

I also measured between this VDD pin and MCU pin 7 (VREF+) which showed also almost 0 ohms. But when i measure between pin 8 (VDD/VDDA) of the MCU and pin 7 OR VDD pin of JP5 it is not a short circuit.

So now i am not sure, if i killed my MCU and if so, why it happend. Maybe because VIN was the main source but i was also plugged in with USB-C cable (maybe for 1 min max)? or because the CAN was still connected but GND was GND of my PC? But CAN is differential......

here is the Baord: NUCLEO-C092RC | Product - STMicroelectronics

an the MCU: STM32C092RC | Product - STMicroelectronics

i am very thankful for help :)

mƎALLEm · ‎2026-04-27

Hello,

In which condition you did measure the resistivity on JP5?: the board is powered on? you should measure the resistivity with the board completely pored of: need to disconnect all the stuff from it: all the external cables and wiring. If you find 2 ohm on JP5, unfortunately there is something broken on the board.

To find what happened to your board:

1- Test U10: the 5V regulator. Remove JP1 and connect VIN between 7 to 12V max and find if you have 5V on JP1 pin 3 like indicated in the above image. If 5 volt is available, U10 chip is OK.

2- Test U9: the 3.3V regulator. If U10 is OK, put JP1 on position 3-4 to select the external source over VIN as power source and remove JP5. Do you get 3.3V? on the regulator side as indicated in the above photo? If yes, I can suspect the MCU is gone.. You can confirm that by removing JP5 and test the resistivity on JP5 pin / MCU side. if it's very low, the MCU is broken..

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

View solution in original post

mƎALLEm · ‎2026-04-27

Hello,

In which condition you did measure the resistivity on JP5?: the board is powered on? you should measure the resistivity with the board completely pored of: need to disconnect all the stuff from it: all the external cables and wiring. If you find 2 ohm on JP5, unfortunately there is something broken on the board.

To find what happened to your board:

1- Test U10: the 5V regulator. Remove JP1 and connect VIN between 7 to 12V max and find if you have 5V on JP1 pin 3 like indicated in the above image. If 5 volt is available, U10 chip is OK.

2- Test U9: the 3.3V regulator. If U10 is OK, put JP1 on position 3-4 to select the external source over VIN as power source and remove JP5. Do you get 3.3V? on the regulator side as indicated in the above photo? If yes, I can suspect the MCU is gone.. You can confirm that by removing JP5 and test the resistivity on JP5 pin / MCU side. if it's very low, the MCU is broken..

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

MaxiTaxi11 · ‎2026-04-27

Hello,

on saturday i measured the resistance between JP5 VDD and one of the GND pins without power. it showed a short circuit. There was also 3V3 between the 2 pins of JP5. I still have power but i killed my MCU. Now i will order parts and won't try messing with two GND potenzial at the same time.... I was not feeling good, when i did this, but now i know for sure, that it was a bad idea.

Thank you for your support