[Discuss-gnuradio] Audio transmittion with USRP

Hello, every one.

I want to use gnuradio and usrp n210 with SBX subdev to transmit real-time audio between two PCs. The flow is as follow:

But it couldn't work well, it always outputs "UUUUUUUUUUUUUU…", no matter what samp_rate I set (1M, 48K, etc). I've tried to use Google to search for solutions, but there is no available one, so I ask for help here, I'll appreciate for your help.