Hi, What do we see in your example? Have you divided the clock by 10? Is the output stable or are the edges jittering anything?
When I look at our clock outputs (in a very quick measurement) they are all approximately in phase but the edges are jittering quite a bit, and I would assume that to different usrp2s could in a worst case be as far apart as half a clock cycle... Regards, Ulrika > -----Original Message----- > From: discuss-gnuradio-bounces+ulrika.uppman=foi...@gnu.org > [mailto:discuss-gnuradio-bounces+ulrika.uppman=foi...@gnu.org] > On Behalf Of MarcW > Sent: Thursday, February 18, 2010 6:51 PM > To: Discuss-gnuradio@gnu.org > Subject: [Discuss-gnuradio] Syncronous data aquisition using > multiple USRP2 boards > > > I am trying to syncronise data acquisition for 3 USRP2 boxes > at 2.4GHz to aquire say 1M samples from each board and write > to a text file. So far I have managed to modify the firmware > to output the USRP2 clock to the debug pins and to call > config_mimo(WE_LOCK_TO_SMA) and sync_to_pps(). When I connect > a 10MHz 2v Pk-Pk sine wave to each board (No PPS signal) and > look at the clock output pin for each there is no drift in > waveforms with respect to one another and the external clock > reference. However, there is a phase offset between the clock > edges on each board which changes every time they are reset > (sometimes of half a clock period). > > Please see the example which includes the external clock > reference and 3 clock outputs. > > Wont this mean that I have unsyncronised sampling since the > ADC is controlled by the position of the clock edge? > > Is there a way to overcome this problem? > > My current python script to read in parallel is derived from > the example /gr-utils/src/python/usrp2_rx_cfile.py using > gr.hier_block2 to create multiple flow graphs (usrp2 -> text > file replicated four times). Do I need any special > syncronisation functions in here or should the problem be > fully handled on the firmware/FPGA? > > Best regards, > Marc. > > http://old.nabble.com/file/p27642862/scope_plot.jpg > -- > View this message in context: > http://old.nabble.com/Syncronous-data-aquisition-using-multipl > e-USRP2-boards-tp27642862p27642862.html > Sent from the GnuRadio mailing list archive at Nabble.com. > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
