Am 30.06.2011 um 11:27 schrieb Ralf: > Am 29.06.2011 16:34, schrieb Marcus D. Leech: >> On 29/06/2011 9:11 AM, Ralf wrote: >>> Hi, >>> >>> the simple GRC in the attachment creates lots of underflows on our E100 >>> ("U" on console) >>> and dropouts when looking at the spectrum. >>> >>> Is this as expected or how can this overload of the embedded Linux be >>> avoided? >>> >>> Thanks, >>> Ralf >> Well, for one, 60Khz isn't a proper divisor of the 128MHz sample rate of the >> DAC, which means it can't be properly interpolated. >> >> The minimum sample rate that you can deliver to the USRP-E100 is 128MHz/512 >> = 250kHz, so you'll have to interpolate your >> data stream up to 250kHz prior to "presentation" to the UHD sink block. >> > > Hi Marcus, thanks for your reply. > > That is very important for us to understand. How is the divider 512 > determined? It is in the FPGA I suppose. > Where can read more about the FPGA besides this small text? > http://www.gnu.org/software/gnuradio/doc/exploring-gnuradio.html#fpga > > Can we only put proper divisors of 128MHz in terms of datarate into the UHD > sink even above 250kHz? > > Actually we need to put ~10kbit/s of data onto a ~400kHz carrier. Is the GRC > repeater the right functionality > to interpolate the small datarate as shown in the attached setup? > > Regards, > Ralf
There is a collection of lots of internal details of the USRP1 under www.gnuradio.org/redmine/attachments/129/USRP_Documentation.pdf They might also apply to the operation of the E100's FPGA logic. You can also look at the source code directly http://ettus-apps.sourcerepo.com/redmine/ettus/projects/uhd/repository/revisions/master/show/fpga Regards, Matthias _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio