On 07/09/2017 12:15 PM, Andy Walls wrote: > On Sat, 2017-07-08 at 21:38 -0400, Andy Walls wrote: >>> Date: Fri, 7 Jul 2017 19:50:55 +0300 >>> From: HLL >>> Hi all, >>> >>> I'm relatively new to DSP and gnuradio but I tried tons of stuff >>> and >>> I couldn't decode a fairly simple FSK data. >>> baudrate seems around 600-700 bps and fsk deviation is less then >>> 3k. >> >> >> Hmmm. I took a look at your signal and tried building a coherent 2- >> FSK >> demodulator. Under the assumption that it was straight 2-FSK, the >> signaling tones looked to be at +/- 1200 Hz when properly centered.
Just to be clear - doesn't 2FSK have 4 tones? I'm not sure what you mean by signaling tones. I just looked at it in inspectrum and there are 4 visually identical structures - and I would guess the fact there are 4 structures is just a coincidence. They're roughly 1.45 seconds long with blank spacers varying from 116 ms to 200 ms. I must be doing something wrong. -- Cinaed >> The >> fastest bit rate appeared to be 1880 bits/sec. >> >> But in reality that doesn't work. I could never get good symbol >> timing >> recovery as the "FSK" signal appeared to have two different baud >> rates. >> >> After some reflection, the signal you have appears to actually be >> AFSK >> inside of FM. Zoom out a little on the output of the quad demod, and >> your eye can see the two tones. The two tones appear to be at 350 Hz >> and 940 Hz. The tones are unusual in that they are square wave tones >> vs. sine wave. >> >> I haven't worked you the baud rate yet. I'll hack away at it more >> tomorrow. > > It definitely is AFSK in an FM transmission. > > The baseband baud rate appears to be a 233 bits/second. > > The beginning of every packet starts out with the following bits: > > 000000000000000000000000 100 01111110 > > I keyed off of those last 8 bits above (01111110), since they looked > like an HDLC flag character to me. > > The payload bytes of the 4 packets in the file (after that 01111110 bit > pattern) are: > > 6884485b066e7505647e875a4ac70c74447474477e47e5f85c47065f44be79a74e67a6a452bfffffffff > 68c4485b062c7565e67227564ac74e74247478477447e5f85ce7065f44be75a74867a6ec52dfffffffff > 68c4485a278e6f856e7006706a470c7fa4f67c057c47e7f06f47447f66ae7d867048874243dfffffffff > 68c4485a278e6f85ec70a67a6267cc7fa4f678257647e7726fe7447f662c7d8670488700437fffffffff > > The ff's at the end are the space after the end of the packet. > > > Try the attached GRC file. > > For it to work, you will need to build and install: > > 1. A relatively recent GNURadio > > 2. The gr-nwr OOT module found here: > https://github.com/awalls-cx18/gr-nwr > You'll have to write your own PyBOMBS recipe file, if using PyBOMBS to > build GNURadio and OOT modules. > > 3. The gr-reveng OOT module found here: > https://github.com/tkuester/gr-reveng > > Regards, > Andy > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
