I am programming a stm32 (2 wire SWD: SWDIO and SWCLK) series MCU with a st-link V2 i cut off a nucleo board. I usually just connect the 3V3 supply off of my arduino, but atm i am trying to make a box with the j link in it, and the 3V3 supply coming out of a SMPS. to be clear, rathen than powering the PCB up using its power ports, I just connect the Vcc net and Gnd net of the MCU on the pcb to my supply.
The error message mentions that the firmware could not restart the target MCU. However, when I connect my arduino back again, it works fine. This happens as soon as I connect my ST link to my PC, when it usually opens the device as a storage, but only this time with the mentioned error message.
This worked perfect with my arduino, but not with my SMPS. Is there a reason? might it be a current surge damaging the st-link?