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From: | 周亮 |
Subject: | [Discuss-gnuradio] Delay of synchronization with PPS and UHD on USRP2 |
Date: | Fri, 21 May 2010 16:39:35 +0800 |
Hi, These days I am trying to synchronize two USRP2 with PPS signal and UHD. The two USRP2 is connect with same reference clock and PPS signal. I use function "set_time_next_pps(uhd::time_spec_t(0))" to set time to be zero, and make two USRP2 start sampling after 3 seconds. The result shows that there is still phase difference, which means a delay( about 30ns) between USRP2s. I used 10MHz reference clock as input and set DDC frequence to 10MHz. Then I get two complex DC signal. The phase difference is about 0.3*2pi. It seems that the PPS impedence difference between USRP2s is the reason of delay. Any clues or solution??? By the way, the stream mode " STREAM_MODE_NUM_SAMPS_AND_DONE" does not work with "set_time_next_pps" function. It works with "set_time_now". But stream mode " STREAM_MODE_START_CONTINUOUS " works well with "set_time_next_pps" function. Thank you! Liang 使用新一代 Windows Live Messenger 轻松交流和共享! 立刻下载! |
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