Re: [Discuss-gnuradio] FM Receiver

[Tom Rondeau]

On Thu, Feb 24, 2011 at 10:28 PM, Anoth <address@hidden> wrote:
>
> Yes, you must be right, I must have made a mistake when I set up the flow
> graph. How do you know the sample rate delivered by the UHD and how is the
> Polyphase Resampler implemented into the flow graph ?
>
> Francois

Not entirely sure how to do this in GRC... When you set the sample
rate of the UHD device, you can request back what it was actually set
to using "get_samp_rate". So if you were doing this just in Python,
you can have:

req_sr = SR
act_sr = uhd.get_samp_rate()
resamp_rate = req_sr / act_sr
resampler = blks2.pfb_arb_resampler(resamp_rate)

Unless, of course, it's "resamp_rate = act_sr/req_sr". I've been
working too long today to reason that out.

I'm sure there is a way to do this in GRC by knowing the name of the
UHD device and using it; I've just never done it.

Tom



> Tom Rondeau wrote:
>>
>> On Thu, Feb 24, 2011 at 7:17 PM, Anoth <address@hidden> wrote:
>>>
>>> Hi Josh,
>>>
>>> Yes, I have already though about that and I tried to match the sample and
>>> sound card rates without success (but I might made a mistake). I have
>>> also
>>> read on the Internet that it might come from the sound card which cannot
>>> support all rates but I did not find anything more about that subject.
>>> Here
>>> the python code generated by GRC :
>>> http://old.nabble.com/file/p31009164/wfm_rx.py wfm_rx.py
>>>
>>> Francois
>>
>> I think Josh is right and it's a sampling rate error. When you set the
>> sampling rate of the USRP, ask the UHD driver what the current
>> sampling rate is. Use what it returns to you to adjust the sampling
>> rate properly. I ran into this same issue and solved it by using the
>> pfb_arb_resampler block (Polyphase Resampler in GRC) to adjust the
>> rates correctly.
>>
>> Tom
>>
>>
>>> Josh Blum-2 wrote:
>>>>
>>>>
>>>>>>>> gr_fir_ccc: using SSE
>>>>> aUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaU
>>>>>
>>>>
>>>> These characters being printed means that you have mismatched sample
>>>> rates between your USRP device and sound card. Could this be the case?
>>>>
>>>> -josh
>>>>
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>>>
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