Re: [Discuss-gnuradio] USRP1 questions

[Nick Foster]

Use the advanced tuning parameters.

http://files.ettus.com/uhd_docs/manual/html/general.html#tuning-notes

2011/12/12 osama mohamed <address@hidden>:
>
>
>> Date: Mon, 12 Dec 2011 08:07:57 -0800
>> From: address@hidden
>> To: address@hidden; address@hidden
>> Subject: Re: [Discuss-gnuradio] USRP1 questions
>
>>
>>
>>
>> On 12/12/2011 01:52 AM, osama mohamed wrote:
>> >
>> > hi all,
>> > i am using USRP1 with basic tx and rx boards and i have been suffering
>> > some problems recently so i hope you could answer the following
>> > questions(even if not all of them)
>> >
>> > Q1:
>> > when i run the examples tx_timed_samples.cpp and tx_burst.cpp i don't
>> > get any output i tried various sampling rates and amplitudes but they
>> > still didn't produce any output if there is a certain configuration
>> > (i.e. sampling rate and amplitude) that works kindly inform me also i
>> > would like to know the output i am expected to see?
>> >
>> >
>>
>> Those are examples apps to demonstrate API usage. See tx waveforms or tx
>> samples from file for examples that transmit.
>>
>> > Q2: i would like to tx a signal by setting the NCO frequency on the
>> > codec chip through the class codec_ctrl instead of using the PLL, is
>> > this doable or not and ,if yes should i use the class multi_usrp or i
>> > have to jump to the lower level class usrp1_impl?
>> >
>> >
>> If you have basic TX and usrp1, the only frequency translation occurs in
>> the codec. There is no PLL.
>>
>> > Q3: can i use the low level class usrp1_impl to do the same
>> > functions of the examples tx_timed_samples.cpp and tx_burst.cpp
>> > through setting the frequency tuning word of the codec through the class
>> > codec_ctrl ?
>> >
>> >
>>
>> The implementation is not exposed. You will need some "creative" coding
>> if you want to access the internal objects.
>>
>> What do you think is missing in the "multi_usrp" wrapper?
>>
>> > Q4: as i understand from the constructor of the class usrp1_impl the
>> > sampling rates of the tx path are automatically detected and assigned
>> > through this constructor is this true or i have to set them through a
>> > certian function?
>> >
>> >
>>
>> You should manually set the desired sample rate through the API.
>> See
>>
>> http://files.ettus.com/uhd_docs/doxygen/html/classuhd_1_1usrp_1_1multi__usrp.html#ab8bc17744d3ee94b7c5cdcb75457bd6b
>>
>> -Josh
>
>
>
>
>
> hi Josh,
> thanks a lot for your support.
>
> the problem with the "multi_usrp" wrapper is that if i use another board for
> example WBX it will generate the desired frequency through the PLL except
>
> for frequencies less than the minimum threshold (which is as i remember 62
> MHZ for WBX) so in the later case it will set the PLL to the minimum
>
> frequency (i.e. 62 MHZ) and will compensate the difference through the NCO
> (as i understand)
>
> i want to do the same by myself even if the target frequency is in the
> supported range by the WBX (for example : i want to set the PLL to 935 MHZ
> and
>
> tune the NCO by +or - 44MHZ to get the up and down link ranges of the GSM
> system ), the reason for using the NCO instead of the PLL is that the NCO
>
> tuning is instantaneous unlike that of the PLL which takes about 200 micro
> secs
>
> i think this request is not supported by the "multi_usrp" wrapper ??
>
> thanks,
> osama riad
>
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