[App_rpt-users] RTL_SDR for receive

[KD2NFC - Joe]

I could use some help to connect the dots here. 

 

I was trying to use a rtl-sdr to pipe a receive signal into the input or
receive audio for asterisk instead of using the mic in on the usb audio fob.


 

Heres what I got so far. I can get a rtl-sdr installed in the Arch Linux by
using pacman -s rtl-sdr. 

 

Install reboot and plug in rtl-sdr.  You can run lsusb to see if the
computer sees it or run rtl_test. 

 

Now to get the audio piped to audio device in the computer we have to create
a loopback right? 

 

So 

 

modprobe snd-aloop

 

to get the loopbacks setup but its not the usb audio but on the card1??

 

 

Then if you run this command, it will pipe a FM 12Khz bandwidth centered on
446.160 mhz and pipe it to the loopback device which is the device name of
the loopback.

rtl_fm  -M USB -f 446.160M -A fast -s 12K -p -0 -g 0.0 | aplay -r 12k -t raw
-D default:CARD=Loopback -c 1 -f S16_LEaplay -r 12k -t raw -c 1 -f S16_LE

 

 

I added these two items in rc.local so rtl-sdr input and loopbacks are setup
before asterisk starts. 

 

 

After doing some reading. https://github.com/sm0svx/svxlink/issues/250
<----took some notes from here. 

 

I added the input and output device name in the alsa.conf

 

In asterisk/alsa.conf define the audio ports pointing to alsa loopback
devices: 

 

input_device= default:CARD=Loopback

output_device=default:CARD=Device

 

in modules.conf I enabled chan_alsa.so and after reboot with chan_alsa.so
loaded I get no audio at all. My radio keys up at bootup but I get no
initial greeting, no audio is coming through. Now I wasn't expecting this to
work of the top, I still need to figure out how the node is going to get cos
from the rtl-sdr, I could try to use ctcss but can anyone help me connect
the dots on this with what I have so far. 

 

Thanks,

Joe

Kd2nfc

 

 

 

 

 

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