OP25 questions

[lilrags16]

For the past week or so, I have been researching various SDR P25 Decoders and as of now, OP25 looks to be the most promising. The system I am trying to build needs to read a audio stream from FIFO. From what I have read, OP25 can do this, but mu next question would be this. How can I programmatically find what TGID is present on the voice channel?

I do apologize if this information is on a billboard somewhere I just haven't seen it...

 

[boatbod]

For the past week or so, I have been researching various SDR P25 Decoders and as of now, OP25 looks to be the most promising. The system I am trying to build needs to read a audio stream from FIFO. From what I have read, OP25 can do this, but mu next question would be this. How can I programmatically find what TGID is present on the voice channel?

I do apologize if this information is on a billboard somewhere I just haven't seen it...

The python trunking module knows the tgid. It will send http metadata updates (if configured) so maybe you could build something custom based on that?

 

[lilrags16]

I appreciate the response. Is this trunking module part of OP25?

 

[boatbod]

I appreciate the response. Is this trunking module part of OP25?

Absolutely; there are actually several trunking modules, and which one is used will depend whether your are running rx.py (trunking.py) or multi_rx.py (tk_*.py)

Depending what you're trying to do (and how you plan on going about achieving that goal) you may find it preferable to poke around in icemeta.py since that module already receives updates from trunking when calls are set up and torn down. You could probably write a custom handler and have it pick up the meta messages instead of icemeta then you'd be able to send them wherever you want.

 

[R0am3r]

@boatbod - How do I tell my OP25 installation to use a second RTL-SDR on my Raspberry Pi4? I had a working OP25 system and decided to add another RTL dongle for another app (FlightAware). The FlightAware software works great, but now my OP25 script halts. The error appears to be OP25 not finding the second RTL. Is there a command line switch for rx.py that forces OP25 to see the other RTL?

 

[rlmurray56]

@boatbod - How do I tell my OP25 installation to use a second RTL-SDR on my Raspberry Pi4? I had a working OP25 system and decided to add another RTL dongle for another app (FlightAware). The FlightAware software works great, but now my OP25 script halts. The error appears to be OP25 not finding the second RTL. Is there a command line switch for rx.py that forces OP25 to see the other RTL?

This question probably should be in a new thread, but the answer is in this forum if you do a search you'll find it. Hint: rtl=0, rtl=1. By the way Flight aware grabs the first dongle that it sees. But I guess you already knew that. Hopefully you have set different serial numbers for each dongle as well.

 

[boatbod]

Hint: rtl=0, rtl=1. By the way Flight aware grabs the first dongle that it sees. But I guess you already knew that. Hopefully you have set different serial numbers for each dongle as well.

Yup... use the "args" parameter

./rx.py -l "http:192.168.1.24:8080" --args "rtl=1" --gains 'LNA:36' -S 1000000 -q 0 -d 0 -v 1 -2 -U -T trunk-fire.tsv 2> stderr.2

 

[R0am3r]

Fixed it. Thanks all for the quick assist.

 

[lilrags16]

@boatbod, I have been re-digging through Op25. I have seen that the GRC blocks no longer work/exist in 3.8. Is there any way of feeding into OP25 demod FM data from a FIFO, and having OP25 dump out audio to another FIFO nativily, or would I have to try and roll my own?

 

[boatbod]

@boatbod, I have been re-digging through Op25. I have seen that the GRC blocks no longer work/exist in 3.8. Is there any way of feeding into OP25 demod FM data from a FIFO, and having OP25 dump out audio to another FIFO nativily, or would I have to try and roll my own?

op25 boatbod version does have the capability to take a .wav file as input, pass it through the demodulator and output audio. I added this primarily as a means to replay DSD captures (along with .iq files) but it should be fairly generic. You'd be on your own if you want to get any more complex as far as writing a wrapper app etc.

 

[lilrags16]

op25 boatbod version does have the capability to take a .wav file as input, pass it through the demodulator and output audio. I added this primarily as a means to replay DSD captures (along with .iq files) but it should be fairly generic. You'd be on your own if you want to get any more complex as far as writing a wrapper app etc.

So potentially it could take a wav of the voice channel, and give you an outputted wav of the voice?

 

[boatbod]

So potentially it could take a wav of the voice channel, and give you an outputted wav of the voice?

Not really; it can take a .wav and will output either raw 8khz PCM over UDP, or send audio via Linux ALSA or Pulse Audio libraries.