Hi guys, I have a really strange behaviour.

I have a little program that use a MCP23S17 to read some selector everything has worked well so far but since yesterday I have experienced a very strange behavior.
0. Compile and Load my program (PC or MAC same test result)
1. I connect my Teensy (no pin connected, just teensy) to a PC and I open the serial monitor --- > Everything is OK
2. Disconnect Teensy
3. I connect my Teensy (no pin connected, just teensy) to a MAC and I open the serial monitor --- > Everything go crazy and it read casual status from DIN pin (that is not connected)
4. Disconnect Teensy
Goto 1

I use same usb cable and if I connect teensy to MCP the test result are the same.
I use a MCP Library (https://github.com/sumotoy/gpio_expander) that has worked wery well for a long time.

Some suggestion!?

(I didn't post the code because I don't think it's useful, but otherwise there is no problem)

Andrea