Re: [Discuss-gnuradio] E100 Performance

[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

tx.grc
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