[Discuss-gnuradio] About gr_buffer_add_reader

[Eddie Sun]

Hi list,

I have a USRP N210, running on Ubuntu-10.04, when I try to use the Gnuradio-Companion to make a fm_receiver,

I success generate the python code, but when i try to run it,

it shows 
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terminate called after throwing an instance of 'std::invalid_argument'
  what():  gr_buffer_add_reader: nzero_preload must be >= 0
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what is that mean?

I know that I might have some problem in the flow graph or parameter because I use the old version example(USRP1) which I search on the internet as the reference, can any one help me?

PS  I would like to ask an additional question: If I only have DBSRX RFX1200 RFX1800 these three daughterboards, is that means I can't receive the 100MHz FM Radio Signal by my fm_receiver through the USRP N210 (bandwidth not right)? or there is some other ways ?

thanks,

Eddie