Dear Khalid, the RS232 connection, as you've noticed, is necessary for detection. Without being detected, the GPSDO can still supply a PPS (and 10 MHz clock) over the coax connectors – however, I'm not even sure they will discipline those correctly when not initialized via RS232 by UHD.
Why would you want to unplug RS232? Best regards, Marcus On 03.05.2016 18:02, khalid.el-darymli wrote: > Thanks Marcus. > > OK, I'm communicating with the external Firefly-1A GPSDO unit using an > RS 232 cable. I am able to do so after enabling echoing on RS 232 from > the GPSDO. Would that be a problem? Do I need to completely disable > the RS 232 echoing, even while the RS 232 cable is completely unplugged? > > When the RS 232 cable is plugged-in, N200 DETECTs it as an INTERNAL > GPSDO. When I completely unplug the RS 232 cable on both ends, I am > not getting any messages for detecting neither external nor internal > GPSDO. It only shows the following in the terminal for both N200 devices, > > (1) catch time transition at pps edge > (2) set time next pps (synchronously). > > khalid > > > > > On Tue, May 3, 2016 at 12:20 PM, <[email protected] > <mailto:[email protected]>> wrote: > > The PPS input is conditioned with a: > > http://www.ti.com/product/SN74AUP1T57/description > > Looks to me like it should work just fine. > > > > > > > > On 2016-05-03 10:23, khalid.el-darymli via USRP-users wrote: > >> Hi, >> >> I'll appreciate any help on the following. According to the link >> below [1], the PPS voltage for N200 should be in the range *[3.3, >> 5]* V p-p. >> [1] http://files.ettus.com/manual/page_usrp2.html#usrp2_hw_leds >> >> I am getting a PPS signal through fan-outs from an external >> Firefly-1A GPSDO. I measured the output PPS voltage using a >> scope, and it is *2.52 V p-p* (terminated with 50 ohms). >> >> Would this relatively low PPS voltage work for N200? I am having >> a problem syncing two N200 units (2 LFRX/ 1 LFTX ), and I am not >> sure if this would be the cause? >> >> >> Thank you. >> >> Best wishes, >> Khalid >> >> >> _______________________________________________ >> USRP-users mailing list >> [email protected] <mailto:[email protected]> >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > > > > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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