Re: [Discuss-gnuradio] FM Receiver

[Anoth]

Hi,

I agree that it is a sample rate issue. The USRP sends too many data to the
computer which becomes overrun. As you said, I put a Polyphase Resampler
between the USRP and the WBFM receive blocks (
http://old.nabble.com/file/p31046181/fm_receiver.py fm_receiver.py ). But,
when I execute the flow graph, I get this message :

PCM name: hw:0,0
Access types:
    MMAP_INTERLEAVED     YES
    MMAP_NONINTERLEAVED  NO
    MMAP_COMPLEX         NO
    RW_INTERLEAVED       YES
    RW_NONINTERLEAVED    NO
Formats:
    S16_LE               YES
Number of channels
    min channels: 2
    max channels: 2
    2 channels  YES
Sample Rates:
    min rate:    8000 (dir = 0)
    max rate:   48000 (dir = 0)
      8000  YES
     16000  YES
     22050  YES
     32000  YES
     44100  YES
     48000  YES
     96000  NO
    192000  NO
audio_alsa_sink[hw:0,0]: using S16_LE
>>> gr_fir_ccf: using SSE

>>> Done

Nothing happens and I can no longer see the FFT sink window. By the way,
sorry for the delay of my response, but I have not worked on this project
for a couple of days.

Francois


Tom Rondeau wrote:
> 
> 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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