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OP25 CAI reference
by Matt D 15 Jul '13

15 Jul '13

Hi, I have been unable to find the OP25 CAI reference. Can somebody point me to it? Thanks! -- Matt D ------------

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rs decoder in hdu.cc
by Matt D 15 Jul '13

15 Jul '13

Hey, In the hdu.cc file there is a function 'apply_rs_correction'. I am interested in finding out how this works. What is confusing me is that I know it works. But I have been looking at this code and to me it seems to do essentially nothing??? // apply a different kind of correction void hdu::apply_rs_correction(bit_vector& frame) { // pre-processor if statement that is *always false* (0 == false) #if 0 *// so this code is not included in the final compiled program static itpp::Reed_Solomon rs(6, 8, true); const size_t rs_codeword[][6] = { }; const size_t nof_codeword_bits = sizeof(codeword_bits) / sizeof(codeword_bits[0]); // the end of the pre-processor if statement #endif // and that's it for this function? -- so this function is actually empty in the compiled program??? } I am putting comments in the code trying to understand it. What am i missing here? -- Matt D ------------

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LCWs: hamming, rs, serialization
by Matt D 13 Jul '13

13 Jul '13

Hey, I am trying to get a handle on the data in the Link Control Word. The LCW is 72 bits right? On transmission the 72 bit LCW is serialized into 12 hex bits. And then it is encoded with a (24,12,13) RS code to yield 24 hex bits. The 24 hex bits are then encoded with a (10,6,3) shortened Hamming code to yield 240 bits total. Is it known how the bits are serialized? Or better yet is there an existing function for unserializing/serializing that will work here? And the Hamming and RS codes: does anyone have functions for decoding (10,6,3) Hamming and (24,12,13) RS code? If these decoders do not exist already, where should I start? Thanks! -- Matt D ------------

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Link Control Format
by Matt D 12 Jul '13

12 Jul '13

Hey, Does anyone know whats up with the LCFs??? There are only 2 examples in the Daniels manual. I have been unable to find out anything about the remaining LCFs. Thanks -- Matt D ------------

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algorithm id
by Matt D 30 Jun '13

30 Jun '13

has anyone seen this algorithm id: Unknown (0xa4) ?? -- Matt D ------------

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sending wireshark patch upstream
by Michael Ossmann 26 Jun '13

26 Jun '13

I've had some people request that I submit the P25 CAI Wireshark dissector upstream for inclusion in Wireshark. It makes sense to me since it is quite stable. Do others agree? My only concern is that we currently use an unassigned UDP port and encapsulate P25 CAI in UDP. Should we try to get an official pcap data link type (DLT) instead? Are there reasons to prefer UDP over our own DLT? If so, should we pursue standardizing a UDP port number? Mike

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New (separate) GRC blocks: FSK4, decoder & Traffic Pane [1 Attachment]
by Balint 27 May '13

27 May '13

Hi folks, A quick update: I've added to gr-baz <https://github.com/balint256/gr-baz> some new OP25 blocks. I've split up the combined 'Decoder' block into the FSK4 and actual decoder (simple) parts. I've also added the traffic pane - you'll see how it fits together in the sample/OP25.grc Make sure you back up your old GRC file before you update so you don't end up in a nasty XML merge conflict! For those people that aren't hearing any audio, check if the traffic pane is showing you anything. For those wondering about talk of patches, instructions are here: http://wiki.spench.net/wiki/OP25 If you use r307+patch, you can also check the console to see if decoder information starts appearing to see if valid frames are being detected. Balint

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File source OK but USRP no audio
by souf308 25 May '13

25 May '13

Hi guys. First thank everybody for helping me those previous week. I'm really stuck on something now that I can't understand: When I' using the file source in OP25.grc everything seems working perfectly, I got the 4 ligns in the Dibits and I can hear someone speaking. HOWEVER when I use my USRP B100 here is the situation: I have 4 perfect lignes but NO AUDIO. Moving from the File source to the USRP, I dont touch any audio sink frequency or interpolation of the Rational Resampler or Channel rate so logicaly the probleme should not be coming from here.. Im pretty sure that I applied the patch r307. Furthermore this patch is also to make the audio work wich is the case with the file source so what..? Any suggestions please? Why the audio is working with the files source but not with the USRP? Thank you very much Souf

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Next branch (3.7)
by Matt D 24 May '13

24 May '13

Hi everyone, I am sort of weary of updating to using next branch (3.7) from 3.6.3 because I don't want lose my balance and get dumped. But I was told there is a feature there I may need. So is anyone using OP25 with 3.7 successfully? Cheers, -- Matt D ------------

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data unit handler
by Matt D 22 May '13

22 May '13

Hi guys, I have a pretty straight forward question. In directory op25/blocks/src/lib there is a file called logfile_du_handler.h and the comments within say that the code writes frames to a log file and that the name of the log file is d_log. How do we access this log file? Thanks a bunch -- Matt D ------------

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