I'm trying to learn about the MCP23017 I/O Expander using my Uno board.
I'm following the tutorial here: http://www.learningaboutelectronics.com/Articles/MCP23017-IO-port-expander-circuit-with-arduino.php
There is a statement: "And we connect the address pins, pins A0, A1, and A2, to ground. This makes the address of these 3 pins 000".
I understand the concept of using these three pins to chain more Expanders and how their binary value determines which expander board is the active board, etc. But in the example he is also connecting LEDs to these 3 ports.
How can I connect these ports to ground AND use them for controlling LEDs? It seems to me I can't do both at the same time?