NBFM problem with rtl_fm on Raspberry Pi 2

Hayati Ayguen h_ayguen at web.de
Wed Jul 15 06:26:29 UTC 2015


Hello,

there's no NBFM demodulation problem when using Debian Jessie on Raspi2
http://sjoerd.luon.net/posts/2015/02/debian-jessie-on-rpi2/

and compiling everything necessary on thr Raspi2 itself.
This distri comes with gcc 4.9.2.
Thanks to Murat for his tip to try Jessie.

Now i get useful audio - with some noise in the background, what i have
to check with raw mode.
But it's now understandable audio, what wasn't the case with Raspbian
(based on Debian Wheezy, coming with gcc 4.6.3).

kind regards,
Hayati


Am 08.07.2015 um 21:17 schrieb Hayati Ayguen:
>
> Hello,
>
> now tested the binary compiled on RPi 1 on the RPi 2 - after copying
> the full source including build directory of cmake and executing "sudo
> make install" on the RPi 2.
>
> The result: this works fine!
> Do i have to conclude, that Raspbian's g++/gcc compiler does produce
> wrong code when executed on RPi 2 ?!
> gcc/g++ (Debian 4.6.3-14+rpi1) 4.6.3
>
> OK, now verify: make clean, rebuild and install new binary (from the
> build directory copied from RPi 1):
> this works!  but, i don't understand why!
> Now reboot, so that kernel module reloads:  still works!
>
> In the end, i'm happy that it works "somehow". But, i've no idea where
> the problem lies!
>
> kind regards,
> Hayati
>
>
> Am 08.07.2015 um 09:38 schrieb "Hayati Aygün":
>>  
>> Hi Marcus,
>>  
>> librtlsdr is OK, because rtl_tcp works fine, which transfers full I/Q
>> spectrum of ~ 1.4 MHz to SDR# on Windows/PC.
>> The problem must lie in rtl_fm. By the way, the I/Q demodulation
>> "raw" mode is erroneous, too, when having compiled on Raspberry Pi 2.
>> Something else i could try: use the binary compiled on Raspi 1 B+ on
>> the Raspi 2. I'll check this, this evening.
>>  
>> Before going for painful debugging, it would be fine if someone else
>> could reproduce the problem .. or say that it works fine.
>>  
>> kind regards,
>> Hayati
>>  
>>  
>> *Gesendet:* Mittwoch, 08. Juli 2015 um 08:30 Uhr
>> *Von:* "Marcus Müller" <marcus.mueller at ettus.com>
>> *An:* osmocom-sdr at lists.osmocom.org
>> *Betreff:* Re: NBFM problem with rtl_fm on Raspberry Pi 2
>> Hi Hayati,
>>
>> I'm totally not used to development on Raspbian, but:
>> It's really strange that running the same software on the same distro
>> with the same RF device would give different results.
>>
>> So, debugging is on :/ I'd say you should use rtl_sdr to get raw IQ
>> samples, and then have a look at them on your PC. If they are ok, one
>> would have to look a bit deeper into rtl_fm, if not, something goes
>> wrong on the librtlsdr side of things.
>>
>> Best regards,
>> Marcus
>

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