The two most-common commercial options are Impinj and ThingMagic readers.  Neither are open-source (hardware or firmware) -- they just have APIs. If you go back to the old ThingMagic M5e (rather than newer M6e), there are high-level open source libraries that I wrote:<p>Documentation: <a href="http:&#x2F;&#x2F;wiki.ros.org&#x2F;hrl_rfid" rel="nofollow">http:&#x2F;&#x2F;wiki.ros.org&#x2F;hrl_rfid</a><p>On GitHub: <a href="https:&#x2F;&#x2F;github.com&#x2F;gt-ros-pkg&#x2F;hrl&#x2F;blob&#x2F;master&#x2F;hrl_rfid&#x2F;src&#x2F;hrl_rfid&#x2F;lib_M5e.py" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;gt-ros-pkg&#x2F;hrl&#x2F;blob&#x2F;master&#x2F;hrl_rfid&#x2F;src&#x2F;h...</a><p>You can buy single-chip readers from AMS (eg. on DigiKey) and build your own reader -- not a light undertaking due to RF PCB layouts, but manageable. I&#x27;ve also heard of people using the USRP (GNU Radio) to build gen2-compliant UHF RFID readers, but I believe they require the PCI-bus variant to adhere to protocol timing standards.