For the fellas out in the wild figuring out how to read the serial port on console at least on a bash script here's the link to it: https://pastebin.com/bHic0sBL
Basically on a fresh omega2/+ you need to install at least the stty command package which comes with opkg install coreutils-stty.
Further on the condition you can place an array with strings to compare reading card validation or compare to a file with cards on each line..
You can obtain the lists with your preferred programming language then, node, python, php etc.
Finally with only $20 you can build a linux based access control solution!!