Re: [Discuss-gnuradio] Trying to use the complex int16 option of the UHD blocks

[Nazmul Islam]

Thanks, Josh.

How can I specify the peak from GRC generated Python code? For example, when I select the sc8 wire format, the following code is generated through GRC.

stream_args=uhd.stream_args(
                cpu_format="fc32",
                otw_format="sc8",
                channels=range(1),
            ),

If I want to limit the peak to 0.1 (if the received signal is very weak), can I just use the following?

stream_args=uhd.stream_args(

                cpu_format="fc32",
                otw_format="sc8",
                peak = 0.5,
                channels=range(1),
            ),

Thanks,

Nazmul

On Thu, Jul 26, 2012 at 8:15 PM, Josh Blum <address@hidden> wrote:

On 07/26/2012 05:09 PM, Nazmul Islam wrote:
> Hi Josh,
>
> I am just wondering how the USRP performs the 8 bit mapping for I & Q
> samples. The ADC & DAC have 12 - 14 bit precision, I think. When I select
> the sc8 wire format, does the USRP divide the entire received signal range
> into 2^8 sectors and uses one number to represent each of those?
>

Technically, there is just a multiply and slice operation. You can
specify peak to optimize for the best use of t 8 bits of dynamic range.
See:
http://files.ettus.com/uhd_docs/doxygen/html/structuhd_1_1stream__args__t.html#a4463f2eec2cc7ee70f84baacbb26e1ef

-josh

> Thanks,
>
> Nazmul
>
> On Sun, Jul 22, 2012 at 4:22 PM, Josh Blum <address@hidden> wrote:
>
>>
>>
>> On 07/22/2012 01:14 PM, Nazmul Islam wrote:
>>> Hello,
>>>
>>>  I am trying to use the complex int16 option of the UHD (source/sink)
>>> blocks in my GRC generated python codes. I am doing wide band spectral
>>> analysis in my experiments. Therefore, 50 MS/s will be very helpful for
>> me.
>>>
>>
>> The host format and the wire format are totally independent options
>> here. Both of these properties also configurable properties in the GRC
>> USRP source/sink blocks.
>>
>> * You need to set the wire format to sc8 (thats 2 bytes per complex
>> sample) to achieve 50 Msps over gigabit ethernet.
>>
>> * The desired host format does not have to change. fc32 (complex floats)
>> is a perfectly valid setting
>>
>> -josh
>>
>> _______________________________________________
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>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>
>
>
>

-- 
Muhammad Nazmul Islam

Graduate Student
Electrical & Computer Engineering
Wireless Information & Networking Laboratory
Rutgers, USA.