On 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:
1. Late packet. I use set_time_now and set_start_time command and
after few seconds I see some Ls printed.
2. 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 = 500e3
self.USRP_address = USRP_address = "addr=192.168.10.2"
self.tun_freq = tun_freq= 1.45e9
self.tun_gain = tun_gain= 19
self.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
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're
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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