I have this development board with the following pinout:
And I am using the following FTDI to USB interface to communicate with a PC:
Here is a photo of the board and the FTDI wired to the board pins:
So above on the left two wires are connecting the pins as:
FTDI +5V ---> Nucleo +5V(CN6 pin5)
FTDI GND ---> Nucleo GND(CN6 pin7)
and on the right two wires are connecting UART pins as:
FTDI RX ---> Nucleo PB10: USART3_TX
FTDI TX ---> Nucleo PB11: USART3_RX
So first of all, I assume +5V of the Nucleo board means that it is a 5V power supply for some electronics interface such as sensors. And I also assume that +5V in the FTDI board means that it needs to be powered by 5V supply so it is not a power supply pin but a pin for receiving power.
I do the wiring as I mentioned above and plug the FTDI board to the PC via its USB. The thing is even though I do not power the Nucleo through its own USB port, I still can communicate with the Nucleo's uC through PC.
So how does the uC get power in this case? I am super confused.