Hi, Thank you very much!! I Need to thoroughly go over your response and understand it all, but thanks :)
I also noticed the 2 different in bit timings, I thought it's something electrically, since I noticed the "long" lows and highs are on some specific timings and the shorts have another timing. Before experimenting with the graph (and the said OOT modules). I'm going over it and trying to understand it, what the rotator does, and what it it's role? The part with 2 pll carrier tracking is used for locking the carrier of the low and high freq as I understand (I.E. The cheap digital PWM or clock devider) what is the role of the complex conjugates (mirror over the real axis?), subtract, c-to-f and add part? Are you "subtracting" the (locked) `0` square wave from the `1` square wave, why? I think I understand most of the rest (the `missing block` from their names :) ) Thanks, HLL P.S. FYI, The capture I'v attached contains 4 bursts of 2 devices, 2 from device A and 2 from device B. P.S.2 It is probably some cheapo electronic components or re-using the micro that is already there. On Sun, Jul 9, 2017 at 10:15 PM, Andy Walls <a...@silverblocksystems.net> 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. > > 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: > > 6884485b066e7505647e875a4ac70c74447474477e47e5f85c47065f44be > 79a74e67a6a452bfffffffff > 68c4485b062c7565e67227564ac74e74247478477447e5f85ce7065f44be > 75a74867a6ec52dfffffffff > 68c4485a278e6f856e7006706a470c7fa4f67c057c47e7f06f47447f66ae > 7d867048874243dfffffffff > 68c4485a278e6f85ec70a67a6267cc7fa4f678257647e7726fe7447f662c > 7d8670488700437fffffffff > > 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 >
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