The sigrok suite needs some kind of hardware to interface to the signals you want to examine.
A variety of compatible low cost chinese made logic analyzer products are available for as little as . Sigrok also supports FX2-based oscilloscopes such as the Hantek 6022BE, non-FX2 devices like the Openbench Logic Sniffer or devices that make use of the SCPI protocol, as all reasonably modern oscilloscopes do (Rigol DS1054z, LeCroy WaveRunner, Yokogawa DLM and similar).