I'm new to pi's extending.
I've a MB102 breadboard, coupled with a powersupply.
I plugged a 9V power supply, and it's working (powersupply => resistor => led on).
I'd like to interface some components using the Pi's GPIO.
Because there would be two generators (the pi and the external power supply), how should I cable it ?
I hesitate to connect pi's and powersupply ground together, because I'm not sure how electrical laws apply in this case.
How should I put it all together ?
[Edit]: target cabling: