The Red Pitaya is not yet supported, these are programming notes from Pavel Demin.
To interface with the SDR transceiver application for Red Pitaya: http://pavel-demin.github.io/red-pitaya-notes/sdr-transceiver . It uses a very simple TCP protocol. There are just a few commands to set the sample rate and the frequency. The I/Q samples are single-precision float values. Pavel has already added support for this protocol to the gr-osmosdr and SoapySDR libraries:
The programs using these libraries are Gqrx, CubicSDR, Pothos, GNU Radio.
There is also a ExtIO plug-in (RX only):
So, to interface SDR-Radio with the SDR transceiver application for Red Pitaya, it's possible to use one of the above libraries or just directly add this simple TCP protocol to SDR-Radio.