Re: [Discuss-gnuradio] min. decimation value

[Matt Ettus]

Shravan Rayanchu wrote:
> Hello everyone,
>
> My understanding is that the decimation value for the fpga has to be
> between [4, 256]. In usrp_spectrum_sense.py, when I set the decimation
> values to 16 or 8 (spanning 4Mhz and 8Mhz chunk at once), then
> m.data[0] ...m.data[255] print out fine. However, when I set the
> decimation to 4 (i.e. we will be observing a chunk of 16 Mhz), then
> all the  values data[0] ..data[255] are ZERO.
>
> I am trying to understand why is this the case .. is it that the USB
> is not fast enough for decimation value of 4? I get some "u0"s printed
> out even when I run for decimation values of 16 and 8 ... is this a
> cause of concern?

If you use a decimation value of 4, you need to switch to 8-bit
samples.  The bus isn't fast enough for 16-bit samples with a decimation
of 4.