Nucleo144 with external 3v3 Support. Use of virtual com port possible?

[felix23]

​Hello,

I plan to power the µC of the Nucleo 

-144 board with the 3v3 supply that is available on a t est PCB. I would connect +3v3 to pin 7 on CN8 and pin 16 of CN11.At the same time, I would like to use the ST-LinkV2 for programming of the µC and as a virtual com port during operation of the µC to readout the test data with my PC.However, In the Nucleo Board User Manual (UM1974) on page 22 it is stated, that, if powering the Nucle Board with +3v3, the SB3 and SB111 have to be removed and the ST Link is not powered

• Is it possible, to remove SB3 and SB111 and at the same time power the ST Link V2 externally (via USB) to be able to
  • flash the device
  • Use the virtual com port
• Am I right, that there is no possibility to separate the grounds of the external 3v3 power supply and the Power supply of the ST Link V�? (USB of my Computer)? This would make some isolating device in the Serial wire debug lines necessary…

Thanks for your answer in advance.

[Tesla DeLorean]

If you want an isolated serial connection you're going to have to achieve it with your own hardware.​

[felix23]

Thanks for your answer. I already expected that. However, what about the first part of my question concerning flashing the device and debugging when powering the controller by an external 3v3 supply?