Marcus, I see your point. In GNU Radio flow chart when you instantiate USRP source - you can set out put datatype. The default is complex float - two floats per sample which is 4*2=8 bytes. you mentioned on USB wire we got 2*2 bytes per sample = 4 bytes per sample. so we got double data rate coming out of USRP sink when we process it in GNU Radio. if we have 20 MHz sample rate we got 20*4 = 80 MB/s data rate coming out device. and we got 160 MB/s coming out of USRP Source to the filesystem. Does it make sense ?
-- Vladimir On Tue, Aug 29, 2017 at 11:15 AM, Marcus Müller <[email protected]> wrote: > Hi Vladimir, > > because you're mentioning "float", what you're referring is the data type > on the host, ie. what UHD converts the data that comes in through USB to. > > On the USB cable itself, there's already signed 16 bit integer complex, by > default. > > Yes, you can further reduce that (change the "OTW" data format to sc12, > sc8, whatever your device supports), but it of course reduces dynamic range > / increases quantization noise, so you normally wouldn't want to do that. > > You do that by using an appropriate stream_args_t [1] when getting the RX > streamer. In GNU Radio Companion, you simply select the other OTW format in > the drop down menu labeled "Wire Format". > > Best regards, > > Marcus > > [1]https://files.ettus.com/manual/structuhd_1_1stream__args__t.html > > On 08/29/2017 08:08 PM, Vladimir Rytikov wrote: > > will it help to change data type from float to complex16 to reduce data > rate ? > > On Tue, Aug 29, 2017 at 11:02 AM, Marcus Müller via USRP-users < > [email protected]> wrote: > >> 20 MS/s is already 80 MB/s, which is 0.64 Gb/s. It's not that little data >> to shuffle around! So you already need a halfway decent USB3 setup to do >> that. Also, your computer mustn't be very slow. What is your computer, in >> fact? >> >> Best regards, >> >> Marcus >> >> On 08/29/2017 05:07 PM, Cho, Daniel J (332C) via USRP-users wrote: >> >> Hello – >> >> >> >> I am having issues with overflow with the USRP B210 at 20 MSPS. I am >> using a LiveUSB that has Ubuntu and Gnuradio in it. The gnuradio flow >> chart is just the USRP source going into a file sink with the destination >> being just /dev/null. Since the data is going to /dev/null, there should >> be no reason for an overflow to occur but for some reason, I get one or two >> about every 10 seconds. >> >> >> >> Thanks, >> >> Daniel Cho >> >> >> _______________________________________________ >> USRP-users mailing >> [email protected]http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >> _______________________________________________ USRP-users mailing list >> [email protected] http://lists.ettus.com/mailman >> /listinfo/usrp-users_lists.ettus.com > >
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