2nd external monitor to 2012 macbook pro

Hi,

I'd like to connect a 2nd monitor to my non retina mid 2012 macbook pro. I have a 27" 2560*1440 connected to my miniDP, and I thought I could run another monitor through a usb with a usb/hdmi adapter. I got one from cable matters, but it doesn't work... Before I buy any other cable/adapter (they aren't cheap!), I thought I'd check first what you guys think. I don't need audio on the 2nd monitor, and I won't be playing games or watching videos, just coding.

Thank you.