Forum: GNU Radio max throughput USB 2.0

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feldmaus (Guest)
on 2009-04-12 14:11
(Received via mailing list)
Hi All,

i read the FAQ and the Documentation, but i got some questions
about the maximum throughput.

For the ADC which has 64MHz we get 32MHz if we follow nyquist criteria.
The Documentation tell us the maximum speed results in 32MByte/s.
How do you come from 32MHz to 32Mbyte/s ?

I believe this facts are based on 1Byte pro Time is this correct ?
this means you can only send 1 Byte per Time over USB 2.0 ?
Sorry i am not very familiar with the USB protocol.

The USB 2.0 support 480MBit/s that are 60MByte/s.
So i think the USB 2.0 is not the bottle-neck ?

If USB supports 2Byte pro Time we get (32MHz*(2Byte pro Time))=64MByte/s
?
But this could be result in Problems with synchronous/asynchronous ?

Regards Markus
Vincenzo P. (Guest)
on 2009-04-12 15:13
(Received via mailing list)
Maximum sustained throughput that we have achieved so far, given our
chipsets and the USRP's cypress usb interface
is 32 MB/sec that yields, at 16 bit sample resolution:

32M /  (2 *2) = 8Msps (complex) ==>8MHz bandwidth (Nyquist)

1 factor 2 is for I+Q channels
the other is for 16bit (=2bytes) sample resolution

of course, at the price of halving sample resolution you can get double
bandwidth

vincenzo



feldmaus <removed_email_address@domain.invalid>
Marcus D. Leech (Guest)
on 2009-04-12 17:42
(Received via mailing list)
Vincenzo P. wrote:
> double bandwidth
>
> vincenzo
>
Using 8-bit samples, and a rather beastly machine, I can sustain 16Msps
for my SETI spectrometer application.

--
Marcus L.
Principal Investigator, Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
feldmaus (Guest)
on 2009-04-13 15:51
(Received via mailing list)
Vincenzo P. <wwvince <at> gmail.com> writes:

>
>
> Maximum sustained throughput that we have achieved so far, given our chipsets
and the USRP's cypress usb interfaceis 32 MB/sec that yields, at 16 bit
sample
resolution
Hi Vincenzo,

you are right, but why are we calculating with 32MByte/s and not with
60MByte/s or something else ?
From where comes the 32MByte/s ?

USB 2.0 supports a maximum of 60MByte/s. And although our ADC can
handle 32MHz we coudle use 2Byte pro Sample so we get 64MByte/s.
This would be a little more than USB 2.0 can handle. But maybe there
is a solution to get near to 60MByte/s ?
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