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From: | irene menicagli |
Subject: | Re: [Discuss-gnuradio] Late packet and phase issue |
Date: | Tue, 6 Oct 2015 11:01:00 +0200 |
Something to realize is that if you call set_time_now() on two different USRPs, they'll not agree in detail about the time-of-day. If you'reOn 10/05/2015 10:58 AM, Leonard Foxes wrote:
Hi list,
It's me again.
I use a USRP N210 with WBX daughterboards and loop back cable to connect TX e RX. I have two problems:
- Late packet. I use set_time_now and set_start_time command and after few seconds I see some Ls printed.
- Phase. Phase offset changes between executions. (I'm trying to use set_time_command but nothing changes).
This is my python code about usrp:
self.samp_rate = samp_rate = 500e3self.USRP_address = USRP_address = "addr=192.168.10.2"
self.tun_freq = tun_freq = 1.45e9self.tun_gain = tun_gain = 19self.rx_freq_off = rx_freq_off = 0
self.timeref1= timeref1=time.time()
self.uhd_usrp_TX = uhd.usrp_sink(device_addr=USRP_address,stream_args=uhd.stream_args(cpu_format="fc32",channels=range(1),),)self.uhd_usrp_TX.set_samp_rate(samp_rate)self.uhd_usrp_TX.set_time_now(uhd.time_spec_t(timeref1), 0)self.uhd_usrp_TX.set_command_time(uhd.time_spec_t(timeref1+0.1), 0)self.uhd_usrp_TX.set_center_freq(uhd.tune_request_t(tun_freq), 0)self.uhd_usrp_TX.clear_command_time()self.uhd_usrp_TX.set_gain(tun_gain, 0)
self.uhd_usrp_TX.set_start_time(uhd.time_spec_t(timeref1+1))
self.uhd_usrp_RX = uhd.usrp_source(device_addr=USRP_address,stream_args=uhd.stream_args(cpu_format="fc32",channels=range(1),),)
self.uhd_usrp_RX.set_samp_rate(samp_rate)self.uhd_usrp_RX.set_time_now(uhd.time_spec_t(timeref1), 0)self.uhd_usrp_RX.set_command_time(uhd.time_spec_t(timeref1+0.1), 0)self.uhd_usrp_RX.set_center_freq(uhd.tune_request_t(tun_freq + rx_freq_off), 0)self.uhd_usrp_RX.clear_command_time()time.sleep(0.15)self.uhd_usrp_RX.set_gain(tun_gain, 0)self.uhd_usrp_RX.set_start_time(uhd.time_spec_t(timeref1+1))
Any suggestion will be welcome
Thanks in advance,Leo
using an external 10Mhz and 1PPS reference, you should probably use set_time_unknown_pps(), and make sure that both sides
of this are setting the same time AT THE SAME TIME.
Also, WBX has a 180deg phase-ambiguity. Two WBX boards with the same 10MHz reference, on USRPs with the same notion of time,
will either be in-phase, or 180deg out-of-phase, due to hardware ambiguity in the 2XLO mixer used on WBX.
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