When running the packet loopback example, from version 3.10, it works as expected without SDR involvement. However when using an SDR sink and source I have no luck with it working. I have tried using different configurations of sdrs, frequencies and gain values all known to be working on other topologies. As an example, I can use my Ettus B205 on a OFDM packet topology using BPSK and can correctly send and receive packets bar some padding issues. Using the same UHD with similiar bit rate and gain values on the packet_loopback_hier example yields nothing.
The only error I that I've received is a ursp sink underflow error which should be irrelevant. Included is a link of a screenshot of the example file running. I was told by a colleague that the example has been broken for a while, but if it works under simulation I don't believe thats the case. From what I can tell something is not correctly working on the RX side of the topology, either at the PCS or the HPD. If someone has any knowledge about the example file and what could be causing it to not work in my case, I would be delighted to hear about it.