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I am attempting to modify the provided FSK algorithms to use
a standardized method for determining the transmission error rate. In the
fsk_tx file, I’m trying to use the lfsr_32k_source_s instead of a file
source as the source for the transmitter. In the fsk_rx file, I’m
trying to use check_lfsr_32k_s to determine how accurately the data was
received. I have written modules that will convert shorts to bytes and
bytes to shorts, in order to integrate the lfsr output into the existing FSK
programs. I am also able to transmit a signal using the
lfsr_32k_source_s. However, on the receive end, I am confused about how
to use and where to call the ntotal, nright, and runlength functions to
determine how accurately the data was received. I need these functions to
run after all of the data being transmitted has been received. I was
trying to use benchmark_usb.py as an example. However, I am confused about
what exactly the FPGA_MODE_LOOPBACK is. Also, in the benchmark_usb.py
implementation, ntotal, nright, and runlength are called after the fg.run
command. In the fsk_rx.py, graphs and therefore fg.run are not used, and
I don’t understand how to perform a similar implementation of this in the
fsk_rx.py program. My questions are: 1. What is the USRP digital loop back mode? 2. Using the check_lfsr_32k_s function in the
fsk_rx.py program, how can I call ntotal, nright, and runlength only after
receiving all of the transmitted data instead of immediately after the blocks
are connected? Any insights into these issues would be helpful. Thank you, Michael Q. fsk_rx.py Program: data_rate =
options.data_rate
self.samples_per_symbol = 8 self.usrp_decim =
int (64e6 / self.samples_per_symbol / data_rate) self.fs =
data_rate * self.samples_per_symbol payload_size =
1024 #
bytes print
"data_rate = ", eng_notation.num_to_str(data_rate) print
"samples_per_symbol = ", self.samples_per_symbol print
"usrp_decim = ", self.usrp_decim print "fs =
", eng_notation.num_to_str(self.fs) max_deviation = data_rate
/ 4 u = usrp.source_c
(0, self.usrp_decim, 1, options.mux, 0) u.set_rx_freq (0,
-options.cordic_freq) u.set_pga(0,
options.gain) u.set_pga(1,
options.gain) filter_taps
= gr.firdes.low_pass
(1,
# gain
self.fs,
# sampling rate
data_rate / 2 * 1.1, # cutoff
data_rate,
# trans width
gr.firdes.WIN_HANN) print "len =
", len (filter_taps) filter =
gr.fir_filter_ccf (1, filter_taps) k = 1
fmdemod =
gr.quadrature_demod_cf (k) corr =
gr.simple_correlator (payload_size) bytes_to_shorts =
howto.bytes_to_shorts () stream_length =
8*1000000 # length of stream to examine in bits head = gr.head
(gr.sizeof_short, stream_length/16) check =
gr.check_lfsr_32k_s () ntotal =
check.ntotal () nright =
check.nright () runlength =
check.runlength () print
"ntotal =", ntotal print
"nright =", nright print
"runlength =", runlength print
"delta =", ntotal - runlength self.connect (u,
filter) self.connect
(filter, fmdemod) self.connect
(fmdemod,corr) self.connect
(corr, bytes_to_shorts) self.connect
(bytes_to_shorts, check) def main (): app = stdgui.stdapp (fsk_rx_graph,
"FSK Rx") app.MainLoop () if __name__ == '__main__': main () |
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