New device Bresser Air Quality Sensor PM2.5/PM10, PN 7009970

[matthias-bs]

Hi,

I found out that the Air Quality Sensor can be supported with small changes to the bresser_7in1.c decoder. The data field sensor_type (as in other Bresser decoders) allows to distinguish between weather and air quality sensor. Only the actual sensor data would be different:

Weather Sensor (Sensor Type = 1)

static char const *const output_fields[] = {
        "model",
        "id",
        "sensor_type",
        "temperature_C",
        "humidity",
        "wind_max_m_s",
        "wind_avg_m_s",
        "wind_dir_deg",
        "rain_mm",
        "light_klx", // TODO: remove this
        "light_lux",
        "uv",
        "battery_ok",
        "mic",
        NULL,
};

Air Quality Sensor (Sensor Type = 8)

static char const *const output_fields[] = {
        "model",
        "id",
        "sensor_type",
        "pm2_5_ug_m3",
        "pm10_0_ug_m3",
        "battery_ok",
        "mic",
        NULL,
};

What is the preferred way of adding this device?

• Creating a new decoder source file by copying from bresser_7in1.c?
• Adding a new decoder function to bresser_7in1.c?
• Modifying the existing decoder function in bresser_7in1.c and adding or multiplexing (how?) the output fields?

Thanks in advance!

Matthias

[matthias-bs]

Example:

          Byte #: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
        Raw Data: 7E E0 6E BB AA FA 81 AA FA AA FA AA CA AA 2A A9 AA A9 2A AE AA 92 FA AA AA 00 
De-whitened Data: D4 4A C4 11 00 50 2B 00 50 00 50 00 60 00 80 03 00 03 80 04 00 38 50 00 00 AA
                        ^^ ^^ ID
                                    ^ SENSOR_TYPE=8 (raw)
                                     ^  STARTUP | CH=1 (raw) 
                                                 ^ ^^ ^ PM2.5=6
                                                       ^ ^^ ^ PM10=8
                                                                ^ BATT

[zuckschwerdt]

Is it the same CRC? Then I'd use the sensor_type (b[6]?) and split the output with an if

[matthias-bs]

Yes, same CRC. Could you please give a little more detail on how to split the output? Is there an existing decoder which I could use as an example?

[matthias-bs]

Ah, I think I got it now...

[MacH-21]

Hi Can we not use one CRC calc for most Bresser Stations /Sensors?

FYI way back in Issue 1214 feb 12 2021
(For Digest I use CCIT-16 :X16+X12+X5+1 CRCseed = All 0's) which is
CRC-16/XMODEM check-0x31C3 poly-0x1021 init-0x0000 false false 0x0000

You can use https://crccalc.com to test

Raw Data: 7E E0 6E BB AA FA 81 AA FA AA FA AA CA AA 2A A9 AA A9 2A AE AA 92 FA AA AA 00
CRC over 22 bytes 6E BB AA FA 81 AA FA AA FA AA CA AA 2A A9 AA A9 2A AE AA 92 FA AA
7ee0 > CRC = ok

De-whitened Data:D4 4A C4 11 00 50 2B 00 50 00 50 00 60 00 80 03 00 03 80 04 00 38 50 00 00 AA

FROM rtl_433/src/devices/bresser_7in1.c

631d 5c 09 e9 a1 8a ba ab aa aa aa aa a8 ad ac ba cf f9 ca fc aa aa aa      a000000000000000000
631d  > CRC = INVALID should be f05c

10b8 b4 a5 a3 ca 10 aa aa aa aa aa aa aa 8b ca cb aa aa 2a aa aa aa aa      aa0000000000000000 [0.08 klx]
10b8  > CRC = ok

543b b4 a5 a3 ca 10 aa aa aa aa aa aa aa 8b ca cb aa aa 28 aa aa aa aa      aa00000 [0.08 klx]
543b  > CRC = ok

2492 b4 a5 a3 ca 10 aa aa aa aa aa aa aa 8b da cb aa aa 2d aa aa aa aa      aa0000000000000000000 [0.08klx]
2492  > CRC = ok

9a59 b4 a5 a3 da 10 aa aa aa aa aa aa aa 8b da c8 af ea 28 a8 ca aa aa      aa000000000000000000 [54.0 klx UV=2.6]
9a59  > CRC = ok

fe15 b4 a5 a3 da 10 aa aa aa aa aa aa aa 8b da cb ba 38 2a ac da aa aa      aa00000000 [109.2klx   UV=6.7]
fe15  > CRC = ok

2544 b4 a5 a3 2a 10 aa aa aa aa aa aa aa 8b da c8 8a aa aa be aa aa aa      aa00000000000000 [200.000 klx UV=14
2544  > CRC = ok



7in1 outdoor = CRC-16/XMODEM over 22 bytes	
Lightning = CRC-16/XMODEM over 7 bytes	
Leakage = CRC-16/XMODEM over 5 bytes	
PM2.5/PM10 = CRC-16/XMODEM over 22 bytes


6in1 outdoor = CRC-16/XMODEM over 15 bytes
F043 19 10 00 0F 18 FF FF FF 20 98 FF FF FF FF 01 FD
f043 > CRC = ok

[zuckschwerdt]

The Bresser-7in1 works with CRC-16 of 0x1021? We found it to be a LFSR-16 generator 0x8810 -- but of course that could be wrong.

[matthias-bs]

It makes sense to unify the checksum calculation across decoders if possible. There doesn't seem to be much different in terms of computation effort, though.

[gdt]

@matthias-bs If there is a PR that captures all the useful information in the issue, please close the issue. Otherwise, please add a comment summarizing what's in the issue and not the PR, why, and what you think the way forward is. Thanks!

[matthias-bs]

See #2698

[ME-DataStudio]

I have a Bresser air quality sensor and a rte-sdr v3 dongle. The PM10 value from the decoder seems to be wrong. The value on my lcd-display with the sensor gives other values. I tried to get some examples but the -vvv gives a lot of output so when I figured out how to catch only the air quality I will post an example

[zuckschwerdt]

the -vvv gives a lot of output so when I figured out how to catch only the air quality

Try -R 173:vvv

[Mart124]

For those who wonder, Bresser PM2.5/PM10 device, PN 7009970, runs a Sensirion SPS30 sensor 👍

[matthias-bs]

@Mart124 Yes indeed! There seems to be a third ppm/m³ measurement value (probably PM4) and three more values (presumably the number concentration values - #/m³) in the radio message. I set up a Python script for analyzing the sensor output (SPS30 UART TX output) and comparing it against the radio message. Still work in progress...

See matthias-bs/BresserWeatherSensorReceiver#97 (comment)