Consider the following sketch. With nothing connected to the input ports, this prints "1111111111111111". If I apply 3v to the first port, it still prints "1111111111111111". If I apply ground to the first port, it prints "0111111111111111". I would like it to be the opposite. With nothing conne…

Why are MCP23017 (port extender) input pins high by default?

Grumpy_Mike December 23, 2018, 4:52pm 5

or a resistor required

Yes.