Did I break my Nucleo-C092RC ?

[MaxiTaxi11]

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]

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..

[MaxiTaxi11]

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