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[Discuss-gnuradio] detect PPS every second for synchronization
From: |
Yan Nie |
Subject: |
[Discuss-gnuradio] detect PPS every second for synchronization |
Date: |
Wed, 02 Nov 2011 18:43:29 -0400 |
Dear all,
I ma using USRP N200 with LFTX & LFRX +UHD to build up a transmitter and
receiver. The transmitter and receiver are working well if continuously running
without changing the USRP configuration. I am trying to use a GPS as the
synchronization signal for signal reception, which is detecting the GPS pulse
every second and using this pulse to trigger the signal reception.
I am using the 'set_clock_config' to set the PPS clock while the flow graph for
receiver is built. The negative edge of the GPS pulse could be detected when
the flow graph for receiver start running. I am wondering how to continuously
detect the GPS pulse every second and use it as PPS signal to trigger the
signal reception, so that the receiver could be able to synchronized with other
device using GPS pulse. I tried to create a separate thread after the receiver
flow graph start running: (but this approach gives the USRP2 overrun result)
def pps_setting(tb)
while (1):
#pps clock configuration
tb.clk_cfg = uhd.clock_config_t()
tb.clk_cfg.pps_source = uhd.clock_config_t.PPS_SMA
tb.clk_cfg.pps_polarity = uhd.clock_config.PPS_NEG
tb._u2source.set_clock_config(tb.clk_cfg, uhd.ALL_MBOARDS)
tb._u2source.set_time_unknown_pps(uhd.time_spec_t(0.0))
tb.set_sample_rate(tb.sample_rate_rx)
tb.set_freq(tb.freq_rx, tb.lo_offset)
time.sleep(1.0)
1. I am wondering what is the problem? or how to detect the GPS pulse every
second and use it to trigger the signal reception every second for 0.5 second
signal receiving duration.
2. The same question for RF frequency changing. if I would like to change the
RF frequency every second, what could be the best approach?
Thank you so much!
Thanks,
Yan
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