Tom, I really appreciate your reply. I got another question, how to pause the system for 5 milliseconds? I'm trying to transmit signal then suspend the system without any signal transmission for about 5 milliseconds. The following is the part of code that I use to implement this, but it doesn't really work as what I expected.
payload_13bit = '\x01\x01\x01\x01\x01\x0' while(start_flag == 1) msg_13bit = gr.message_from_string(payload_13bit) top_block._ls_msgq.insert_tail(msg_13bit) time.sleep(0.005) Could you please help to see what the problem here? Why it cannot stop the transmission for 5 milliseconds. Really appreciate your help. Thanks, Yan On 02/18/11, Tom Rondeau <trondeau1...@gmail.com> wrote: > > On Thu, Feb 17, 2011 at 7:06 PM, Yan Nie <yn...@uwo.ca> wrote: > > Dear all, > > > > I'm trying to feed the received signal from USRP to a low-pass filter and > > sink the filtered signal into a data file. > > > > The received signal is in complex format. The receiver is built as: > > > > u = usrp.source_c(0) > > coeffs = gr.firdes.low_pass(1.0, 500e3, 20e3,.5e3,gr.firdes.WIN_HAMMING) > > lpf = gr.fir_filter_ccf(1,coeffs) > > dst = gr.file_sink(gr.sizeof_gr_complex,rxlpf.dat) > > connect(u, lpf, dst) > > > > I got a ValueError: unable to coerce endpoint > > > > Without the low-pass filter plugged in, if only feed the received signal > > into a data file, the system is running well. By checking the output from > > the USRP is complex signal and data sank into the data file is complex, > > therefore, the input and the output of the low-pass filter are both > > selected as complex type. Why does this ValueError show up? How to solve > > this error to plugged this low-pass filter in? I really appreciate any idea > > related to this. > > > > Wish you a great day! > > > > Yan > > > Yan, I don't know. I copied the above script and it works fine for me. > I'm a bit confused about two aspects of the code, though. First, you > have the second input to file_sink as just rxlpf.dat, which looks like > the name of a file, but it is not quoted. Was this just a > transcription error? > > Also, in your connect statement, you don't use "self.connect()" or > "tb.connect()" where 'tb' is a top_block object you have created. > What's really going on here? > > Have you tried to make this script in the gnuradio companion? It > should be very simple to put this one together there, and GRC takes > care of the connections and everything else. > > Tom >
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