AmbientWeather-TX8300 & unmanaged encoding

I have the aforementioned device and although r433any detects it and seems to be detecting the timings, it is not able to decode any of the data (from what I can tell, one of the bits may be a bit long?). rtl_sdr detects and decodes it fine. I noticed that there was an issue opened a while back for another unmanaged encoding device and the opener was able to get their issue resolved but, unfortunately, I don't understand the solution well enough to adapt it for my device.

The information as output by 01_main is as follows.


    Data: 

-----CODE START-----
// [WRITE THE DEVICE NAME HERE]
rf.register_Receiver(
    <unmanaged encoding>, // mod
    3908, // initseq
    0, // lo_prefix
    0, // hi_prefix
    0, // first_lo_ign
    1924, // lo_short
    1924, // lo_long
    1964, // hi_short (0 => take lo_short)
    3904, // hi_long  (0 => take lo_long)
    0, // lo_last
    3908, // sep
    0  // nb_bits
);
-----CODE END-----

The timing info from rtl_sdr is as follows:

https://triq.org/pdv/#AAB10307A40F30994C80809180808081818180818180818080808080818180808081808081818080808081818181818080808180808180818181818180808181818081818080818181818080818081818180818255

(I think this should be enough to see what is occurring but can gather more data if required.)

Thanks.

Hello

Looking at code timings would be easier, like, the ones produced with rf433snif lib.

Anyway, looking at triq.org you posted, what I can say:

It doesn't look like Manchester coding (although it is what is guessed by triq.org) Indeed, assuming the red means "high" and the green means "low": We can see several sequences 'long_high'-then-'short_low'-then-'long_high'. This is not possible with Manchester. By the way the low signal is always of the same duration (short). This, again, cannot be with Manchester.
Encoding looks as if being a variation of TRIBIT. That is, it is as if... ... one bit value (let's call it '0' arbitrarily) is coded by 'short_low'-then-'short_high' ... the other bit value (so here: '1') is coded by 'short_low'-then-'long_high' -> The 'low' is always short, only the high duration is short or long to differentiate 0s and 1s.

While infrequent, there's a few such encodings defined in rcswitch for example.

Bad news This cannot be identified by RF433any. RF433any requires a short be followed by a long and vice versa, to identify TRIBIT. Maybe I should bring this improvement one of these days... ;-) RF433any can identify Manchester, too, but as said above, it is not Manchester.

Good news rf433recv can decode it, with proper settings.

If you submit rf433snif output, I can try to work out what register_Receiver() parameters will work. Indeed the short/high duration is not enough, I also need to see the INIT(or PREFIX) duration + I got to be sure what is 'high' and what is 'low', it is not clear to me on triq.org.

Regards, Sébastien Millet

Thank you. I have some experience with some of this stuff as I was creating hardware and firmware for RFID decoders and programmers in the early 2000s but there has been a lot of water under the bridge since then and things are not as clear as they once were. Once upon a time, I would have worked things up from scratch but using libraries tends to be more productive these days.

As you tell me that rf433recv can decode it, I will redouble my efforts and try and get it working myself. I just need to bang my head against the wall repeatedly until my brain gives in. I'll report back. If I have no luck, I'll get those timings for you. Fortunately, there is code in the rtl_433 repository to work from as well.

This is from ambientweather_tx8300.c fwiw.

1970us pulse with variable gap (third pulse 3920 us).
Above 79% humidity, gap after third pulse is 5848 us.

- Bit 1 : 1970us pulse with 3888 us gap
- Bit 0 : 1970us pulse with 1936 us gap

74 bit (2 bit preamble and 72 bit data => 9 bytes => 18 nibbles)
The preamble seems to be a repeat counter (00, and 01 seen),
the first 4 bytes are data,
the second 4 bytes the same data inverted,
the last byte is a checksum.

Preamble format (2 bits):

    [1 bit (0)] [1 bit rolling count]

Payload format (32 bits):

    HHHHhhhh ??CCNIII IIIITTTT ttttuuuu

- H = First BCD digit humidity (the MSB might be distorted by the demod)
- h = Second BCD digit humidity, invalid humidity seems to be 0x0e
- ? = Likely battery flag, 2 bits
- C = Channel, 2 bits
- N = Negative temperature sign bit
- I = ID, 7-bit
- T = First BCD digit temperature
- t = Second BCD digit temperature
- u = Third BCD digit temperature

The Checksum seems to covers the 4 data bytes and is something like Fletcher-8.

I'm concerned that thing about the humidity might cause problems.

This is the output from the snif. I had to lower the threshold a bit.

Signal duration: 231188 us
  N     LOW,  HIGH
-----BEGIN RF433 LOW HIGH SEQUENCE-----
           ,  2748
000    1896,  3900
001    1892,  2056
002    1784,  3896
003    1892,  3908
004    1888,  1988
005    1844,  3912
006    1884,  1988
007    1864,  3984
008    1796,  1960
009    1880,  2056
010    1792,  4068
011    1728,  1996
012    1868,  1980
013    1868,  1988
014    1868,  3984
015    1808,  4056
016    1736,  1972
017    1884,  2128
018    1720,  3912
019    1888, 70120
020      12,  3696
021       4,   244
022       8,  2164
023      28,   240
024      12,   940
025      12,   232
026      12,  2160
027      12,    24
028       4,   228
029      12,   932
030       4,   220
031      12,   620
032      12,   228
033      32,    36
034       4,   180
035      28,     4
036      12,   864
037      20,    12
038       4,   204
039      72,   240
040       0,   284
041      12,    16
042       0,   248
043      24,   212
044       8,   656
045       4,   196
046      28,     4
047      12,   232
048       8,    16
049       4,   240
050       8,   584
051       8,    36
052       4,   180
053      12,    20
054      12,   836
055      28,    16
056      12,  1132
057      88,   180
058      12,    28
059      16,   232
060      12,   592
061      16,    16
062      12,   200
063      16,    12
064      12,   228
065      12,   292
066      12,    36
067       4,   188
068      20,     4
069       4,    12
070       4,   184
071      24,    20
072      12,   844
073      76,   188
074      84,   576
075      12,   280
076      12,   248
077      12,   272
078       4,   308
079      20,   212
080      64,   232
081       8,    28
082       4,   828
083      48,     4
084      12,   176
085      48,     4
086      12,   204
087      32,     4
088      12,   544
089      32,     4
090      20,   240
091       4,   560
092      16,    12
093      20,   184
094     112,   136
095      16,     0
096      76,   196
097      40,    20
098       4,   224
099       4,   260
100      16,   264
101      20,    20
102      20,   220
103      16,    16
104       4,   220
105      84,   160
106     136,   144
107     100,   560
108      12,   216
109     120,   148
110     120,   196
111      16,    28
112      12,   240
113      16,    20
114       4,   236
115      48,   188
116      28,     8
117       8,   244
118      20,   256
119      32,    16
120       4,   148
121      16,     0
122      92,   140
123     116,   212
124      24,   308
125       4,   216
126     112,   136
127     124,   180
128     108,   208
129      40,    16
130       4,   160
131     128,   168
132      92,   208
133      24,     4
134      20,   212
135      32,     4
136      28,   160
137     136,   124
138     140,   172
139     116,   192
140      24,    56
141       4,   148
142     136,   152
143     108,   228
144      12,   264
145       4,    12
146      40,   168
147     128,   136
148     132,   212
149      24,    16
150       4,   228
151      20,     4
152      24,   164
153     116,   152
154     124,   196
155      24,    28
156      12,   208
157      36,     4
158      24,   500
159      72,   204
160      12,     8
161      24,   228
162      40,     4
163      20,   160
164     124,   144
165     128,   188
166      88,   232
167      32,     4
168       4,   168
169     132,   136
170     128,   172
171      64,     4
172      12,   212
173      96,   160
174       4,     4
175      96,   180
176      88,   196
177      80,   212
178     100,   160
179     132,   136
180     132,   188
181      64,     4
182       4,   212
183      20,   240
184     112,   140
185     136,   176
186     100,   184
187     120,   136
188     144,   144
189     128,   220
190      20,    20
191       4,   220
192      76,   148
193     144,   128
194     148,   168
195     116,   188
196     108,   144
197       4,   332
198      20,     4
199      12,   220
200      32,     4
201      28,   188
202     112,   132
203     160,   116
204     152,   168
205     108,   220
206      68,   164
207     136,   124
208     144,   172
209     112,   172
210     124,   140
211     152,   168
212      96,   188
213      20,     4
214      40,   228
215      72,   176
216      24,     0
217      68,   136
218     128,   168
219     116,   196
220      28,   256
221     108,   152
222     116,   192
223      24,     8
224      36,   196
225     116,   136
226     148,   120
227     144,   196
228      84,   204
229      40,     4
230      36,   144
231     136,   128
232     132,   180
233     116,   192
234     112,   128
235      20,    20
236       4,   260
237      84,   204
238      56,     4
239       0,   204
240      40,     4
241      28,   136
242     152,   132
243     136,   160
244     120,   184
245      20,     4
246      64,   140
247     160,   116
248     152,   160
249     116,   212
-----END RF433 LOW HIGH SEQUENCE-----

This possibly also though it looks fairly different but maybe I'm just not understanding what's being recorded. There are other 433 signals around here but I isolated these to be the device as best I could.

Signal duration: 128392 us
  N     LOW,  HIGH
-----BEGIN RF433 LOW HIGH SEQUENCE-----
           ,  6844
000     384,    92
001     180,   116
002     164,   124
003     144,   132
004     160,   108
005     152,   140
006     136,   140
007     152,   120
008     160,   108
009     168,   100
010     196,    92
011     188,   128
012     140,   124
013     168,   120
014     164,   132
015     152,   128
016     160,   108
017     172,   120
018     136,   152
019     144,   144
020     160,   108
021     172,   108
022     184,   108
023     168,     4
024      48,    40
025     172,   108
026     176,   116
027     168,   128
028     144,   144
029     152,   116
030     176,   124
031     164,   136
032     128,   144
033     152,   124
034     160,   116
035     164,   128
036     176,   116
037     168,    92
038     184,   136
039     136,   136
040     152,   140
041     160,   108
042     172,   112
043     176,   116
044     168,   140
045     148,   120
046     152,   152
047     136,   132
048     152,   136
049     152,   120
050     160,   120
051     160,   136
052     144,   144
053     152,   112
054     164,   116
055     160,   144
056     144,   136
057     152,   160
058     128,   144
059     124,   144
060     152,   136
061     152,   128
062     160,   124
063     160,   160
064     124,   136
065     168,    12
066       4, 10648
067    1964,  6740
068     420,    76
069     208,    76
070     220,    16
071       4,    40
072     212,    12
073      20,    12
074     188,    92
075     180,   116
076     176,     8
077       8,    60
078     220,    12
079      12,    12
080     184,    88
081     196,    92
082     248,    48
083     192,   128
084     144,   124
085     168,    92
086     188,   116
087     188,    92
088     172,    96
089     188,   160
090       4,   300
091      84,   152
092     160,   100
093     180,   100
094     220,    72
095     188,    48
096       0,    24
097     176,   116
098     164,   112
099     164,     0
100       8,    80
101     176,    16
102       4,    60
103     172,   100
104     192,    92
105     236,    72
106     168,   112
107     176,    84
108     204,    84
109     204,    16
110      12,    40
111     236,    32
112     200,    84
113     192,   108
114     188,   108
115     176,    16
116       8,    52
117     172,    96
118     180,   108
119     204,    88
120     196,   108
121     152,   128
122     152,   144
123     116,   168
124     132,   152
125     160,    92
126     192,    84
127     228,    80
128     188,     4
129      12,    56
130     184,    84
131     196,   100
132     196,   100
133     184,   108
134     168,   128
135     152,   108
136     172,     4
137       4,    88
138     180,    28
139       4,    64
140     160,   100
141     188,   100
142     180,   124
143      20,     4
144     116,   124
145     180,    24
146       0, 10604
147    2156,    20
148      20,  6412
149      32,    12
150     456,    48
151     228,    64
152     844,    64
153     212,    84
154     272,    20
155     284,     4
156     188,    80
157     200,    84
158     240,    40
159     256,    64
160     168,    92
161     196,    76
162     248,     0
163       8,     8
164     256,    20
165     204,    72
166     212,    72
167     300,     4
168     236,    16
169     232,    64
170     212,    88
171     240,    12
172      12,     4
173     220,    32
174       4,    12
175     184,   100
176     188,    84
177     292,     4
178     244,     4
179     228,    76
180     220,    72
181     604,     0
182     192,    68
183     220,    72
184     264,    28
185     276,    28
186     184,    76
187     200,   100
188     220,    84
189     220,    12
190       4,    20
191     180,    88
192     212,    80
193     252,    40
194     236,    68
195     168,   100
196     188,    76
197     224,    36
198       4,    12
199     220,     4
200      12,    16
201     204,    76
202     204,    88
203     204,   108
204     196,    84
205     172,    96
206     188,    96
207     212,    92
208     180,     0
209      16,    56
210     176,   124
211     160,   100
212     200,    96
213     188,    84
214     188,    92
215     192,    84
216     200,   116
217     160,   148
218     152, 10640
219    2024,    12
220      20,     4
221       4,  6564
222      48,     4
223     440,    56
224     224,    60
225     852,    48
226     220,    80
227     256,    24
228     532,    60
229     220,    80
230     584,    32
231     192,    68
232     208,    64
233     288,     4
234     532,    64
235     212,    76
236     192,   128
237     196,     4
238       8,    48
239     180,    76
240     204,    80
241     240,     0
242       4,    32
243     492,   100
244     180,    88
245     240,    12
246      12,     4
247     212,    12
248      32,     0
249     196,    76
-----END RF433 LOW HIGH SEQUENCE-----

Hello

About your first posting: it clearly corresponds to the description you give (Bit 1 : 1970us pulse with 3888 us gap, Bit 0 : 1970us pulse with 1936 us gap). Issue is, I see 19 or 18 bits of data, not more. Possibly, the snif start signal was not expecting the correct duration for the "init" sequence (too short criteria) and it started too late, stepping into the train while already in motion. One thing is sure, an INIT sequence of 2748 us would be VERY strange (it is between short and long ; normally INIT is far above the long duration).

If you know how to update snif lib, you might change the "initial signal duration to start recording" for various other durations to get the whole signal. Most frequently, the "init" sequence (not part of encoding, just to say to the receiver "pay attention to what'll follow") is "MUCH LONGER" than the long duration. So here, the long duration being 4000 us, I'd try to start snif after an init signal of 8000 us of 10 000 us or so. Not less than 6 000 us in all cases.

About your second posting, it clearly looks like something "not random", but does not look like an encoding either!!!?? Let me explain: normally an encoding relies on different durations to go over the radio, the decoding consisting in discriminating between different durations to end up with "0s" and "1s". Here, the durations are all too close.

See picture of durations statistical repartition:

You normally will see (with a signal carrying encoding) that durations are split in 2 categories, the short ones and the long ones. Sometimes on low signal, sometimes on high signal, sometimes (most frequent) on both. Given your description, we can expect the low signal to be always of the same length (2 000 us), the high to be split into 2 different categories, the short (2 000 us), the long (4 000 us). In your data there is ONE duration on low signal, ONE duration on high signal!

Conclusion? I can say nothing here sorry. Maybe, the encoding is based on the signal phase? Then, the duration only won't help, as you'd need a receiving device that recognizes the phase to get the data. Or there is some sort of FM-modulation in it? Just random guessing...

Regards

Thanks for taking a look. I'll look into modifying the lib. For now, what I want to do, I can do with the SDR so I'll use that while I look into this. It's also possible the receiver is not very good. I have one on the way that is supposed to be better so I'll have another look when it arrives.

sebmillet / RF433recv

AmbientWeather-TX8300 & unmanaged encoding #12