UPDATE
I just figured out, that the method PollKeyPress(key_pressed) returns -1 when no inputs are recognized. Can someone tell me why it returns -1?
Auto Transmit Key Presses is turned off, so it should only return 0 if no button is pressed and 1 if a button is pressed.

Hello Matrix Orbital Team, i need help with button input from LK204-7T-1U USB-Serial to a CentOS virtual machine. I used the C++ Input/Output example on your website and altered it to fit for linux. I edited the polling to be able to show in real time when pressing a button, showing me which button ...