I had this exact problem when I was trying to connect my 3020 CNC to my computer. Most of these LPT to USB dongles was only designed for using it for LPT rather

I had this exact problem when I was trying to connect my 3020 CNC to my computer. Most of these LPT to USB dongles was only designed for using it for LPT rather than as a parallel port. This pretty much screws up all the signal timing or analogue reading which a lot of old school dongle used to use. I'm pretty sure you can use something like this: https://www.startech.com/Cards-Adapters/Serial-Cards-Adapters/1s1p-USB-Serial-Parallel-Adapter-Cable~ICUSB2321284 https://www.startech.com/Cards-Adapters/Serial-Cards-Adapter... Though I cannot vouch for this since I ended up ripping my control system out and replacing it with something modern. You should talk with a startech representative to make sure before you buy.