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Re: [Discuss-gnuradio] E100 Performance

From: Matthias Wilhelm
Subject: Re: [Discuss-gnuradio] E100 Performance
Date: Thu, 30 Jun 2011 13:48:17 +0200

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

They might also apply to the operation of the E100's FPGA logic.

You can also look at the source code directly


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