On Tue, 06 Nov 2018 09:40:09 -0500
"Marcus D. Leech via USRP-users" <usrp-users@lists.ettus.com> wrote:
> On 11/06/2018 04:12 AM, Gwenhael Goavec-Merou via USRP-users wrote:
> > Hi,
> >
> > My environment is:
> > USRP: X310 with basicRX (currently one but 6 in a near future)
> > UHD: 3.13.1.0-rc1
> > GNURadio: 3.7.13.4-r2
> > gr-ettus: master branch, up to date
> >
> > I need to sample 4 real signal / USRP and to demodulate / decimate before
> > transfer to the PC.
> >
> > I have created a GNURadio flow with:
> > - 2 Radio (id 0 and 1), configured with 2 channels
> > - 2 DDC (id 0 and 1), with 2 channels, with a center frequency fixed to XX
> > MHz
> > - 4 complex To Real;
> > - 1 QT Gui with 4 inputs.
> >
> > Each channel of each radio is connected to an DDC input (radio0 channel 0 to
> > DDC0 input 0, radio0 channel 1 to DDC0 input 1, etc.)
> >
> > With this setup and with an input configured as XX + YY MHz (to have a
> > beatnote) I'm able to see a sinusoid on the qt for all channels (if I plug /
> > unplug an input signal the corresponding plot is equal to 0 or displays the
> > signal).
> > But:
> > 1/ the console panel display continuouly messages about channels overrun
> > 2/ the data flow is not continuous (visible in qt plot) (I suppose is due to
> > 1/ )
> > 3/ channels are not aligned (I suppose is due to 1/ and/or 2/
> >
> > Theorically, by reading HDL files for the X310 firmware it's seems possible
> > to use this configuration.
> >
> > Then, how to fix my issue?
> > - Is it a USRP/UHD limitation?
> > - gr-ettus seems not heavily upgraded, is something must be modified in this
> > repository?
> > - I am just wrong somewhere on my design?
> >
> > Thank you very much
> >
> > Gwen
> >
> What is the sample rate as delivered to the PC? What kind of PC?
The sample rate is 3MS/s for each channels after DDC (200MS/s before due to
the ADC).
My PC is a Lenovo thinkpad x230 with a 1Gb ethernet card.
>
> Overrun means that your PC isn't keeping up with the sample flow.
>
I've just done several test with only 2 channels :
- 2 radio, 1 channel/radio and 2 DDC with 1 input (first on radio0, a second
radio1) :
- data continuous (but not synchronized)
- no message on display panel
- 2 radio, 1 channel/radio and 1 DDC with 2 input :
- console panel displays continuouly "Ooverrun on chan 0"
- data not continuous
- after a short time : freeze
- 1 radio with 2 channels and 1 DDC with 2 input :
- console panel displays continuouly "Ooverrun on chan 0" and "Ooverrun
on chan 1"
- data not continuous.
- 1 radio with 2 channels and 2 DDC with 1 input :
- console panel displays continuouly "Ooverrun on chan 0"
- data not continuous.
So, the first test seems to show it's possible with my computer to receive 2
channel 3MS/s without overrun. Other tests seems to show a problem for radio
and/or for DDC to send or receive the full speed ADC flow.
Thank.
Gwen
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