[Discuss-gnuradio] UHD and gr_block_executor error: "source <gr_block gr uhd usrp source (1)> produced no output. We're marking it DONE."

[Christopher Dean]

Hi All,

I'm working on a program that allows two E100's to communicate over 
radio frequencies.  This program runs well on a pair of N210s, but on 
the On the receiving end, the program has two principle flow graphs that 
both connect to the uhd usrp source.  The first one used (A) is used 
only at the beginning of the program; afterwards, the second flow graph 
(B) is used.  Upon running the program, I'm getting the following error 
messages:

    UHD source block got error code 0x9
    gr_block_executor: source <gr_block gr uhd usrp source (1)> 
produced no output.  We're marking it DONE.

and, much more frequently,

    UHD source block got error code 0x10
    gr_block_executor: source <gr_block gr uhd usrp source (1)> 
produced no output.  We're marking it DONE.

I've tried leaving A and B connected the entire time, connecting B 
before disconnecting A, disconnecting A before connecting B, but none of 
these have alleviated the issue.  The error messages don't typically 
occur until we've switched to B.  Also, I've been unable to find what 
either of these error codes stand for in the GR and UHD documentation.

I get this error whether I'm running the program on one or both of the 
E100s.  Even when I'm only running it on one of the E100s, it should 
definitely be detecting something at the rx port, since I'm running it 
directly there from a noise generator.

Do you have any idea what these error codes mean or why I might be 
getting these errors?

Thank you very much for your help,

Chris