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[Discuss-gnuradio] Sync 2x USRP2s


From: David Evans
Subject: [Discuss-gnuradio] Sync 2x USRP2s
Date: Fri, 19 Mar 2010 14:48:33 +0000
User-agent: Thunderbird 2.0.0.23 (Windows/20090812)

Hi,

I want to sync two USRP2s, and currently trying to modify the VRT rx_timed_samples...

usrp2::clock_config_t cc;
cc.ref_source = usrp2::clock_config_t::REF_INT;
cc.pps_polarity = usrp2::clock_config_t::PPS_NEG;
cc.pps_source = usrp2::clock_config_t::PPS_SMA;
cc.provide_ref_to_mimo = false;
u2->config_clock(cc);

// u2->set_time(....); // replaced with...
u2->set_time_at_next_pps(...);

However, the code hangs at the start sampling, and manually applying a pulse to the PPS SMA does nothing.

What is the correct voltage level and pulse shape required? Manually toggling anything between 0-1.5v and 0-5v does nothing. I hope 5V isn't too much!!!

Ultimately, I want to capture coherent samples with both USRPs, maybe with the MIMO cable, and a GPS reference + PPS. Would this be just a case of...
For USRP A (with ref + PPS attached)...
 cc.ref_source = usrp2::clock_config_t::REF_EXT;
 cc.pps_polarity = usrp2::clock_config_t::PPS_NEG;
 cc.pps_source = usrp2::clock_config_t::PPS_SMA;
 cc.provide_ref_to_mimo = true;
For USRP B...
 cc.ref_source = usrp2::clock_config_t::REF_EXT; ***MIMO???***
 cc.pps_polarity = usrp2::clock_config_t::PPS_NEG;
 cc.pps_source = usrp2::clock_config_t::PPS_SMA; ***MIMO???***
 cc.provide_ref_to_mimo = false;

Kind Regards,
David









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