I want to use RS232 with open/closed circuit (e.g. door open/shut) of whatever pins as input and get related string or number as output. I want to achieve that without extra IO hardware.
Example: door shut (circuit which 2 pins on RS232?) and get e.g. a "1" as output on the PC screen with e.g. cat /dev/usb/tts/0.
How can I achieve that?
I am using a usb to serial adapter.