This project uses a Magtek USB card reader, lsusb reports it as Bus 004 Device 015: ID 0801:0001 MagTek Mini Swipe Reader (Keyboard Emulation). If you have a different one, use lsusb to find out these values, and put them in the config.json file. lsusb reports them in hex, so prepend 0x to them.
The magtek documentation is located here: http://www.magtek.com/docs/99875206.pdf. Another implementation of this code written by jness on github is located here: https://github.com/jness/magtek_cardreader/blob/master/main.py.
I used that implementation to inform this new implementation. I found that the while True: polling loop that is uses is too taxing on the CPU to use on a Raspberry Pi, after many hours it tends to crash. node-hid's callback structure is a lot less so.
Since there is no other data used other than a card swipe, there is no way to use a salted hash. Therefore, the cards are hashed using sha512 with no salt. This will be changed to scrypt in the future.