[New protocol] 433.92 MHz, AM270: Wittime WT2022A wireless hygro/thermometer (3 channel)

[digitalcircuit]

In brief

Item	Value
Product	WT2022A thermo & hygro sensor for Wittime 2180/etc weather stations
Frequency	433.92 MHz
Modulation	AM270
FCC ID	2AJOATX2022C: list of exhibits, FCC application
Source	Wittime 2180 weather station: https://smile.amazon.com/dp/B09QKVNTC7/ ($30 as of 2022-7-10)

Details

As described in the manual linked from the FCC exhibits, the Wittime outdoor sensors report temperature and humidity data roughly every 57 seconds over one of three selectable channels: 1, 2, 3. There’s no way to force an update other than removing and reinserting the battery.

No pairing appears to happen with the transmitter, the receiver seems to simply synchronize when it turns on its antenna for power-saving reasons.

I’ve attached the raw recordings of multiple temperature/humidity broadcasts on all three channels - channel 1, 2, and 3. It’s possible that other devices using this protocol provide more than 3 channels.

I’ve also confirmed that these files when played back on the Flipper correctly replay the recorded weather data (temperature and humidity) to the receiving weather station.

Supporting this protocol could allow the Flipper to receive hyper-local weather broadcasts from anyone who happens to have a similar device. It’d also enable displaying custom numerical data on one’s own weather station via any unused channels.

Recordings

Please let me know if you need anything else!

This is not a traditional remote. 10× transmissions in one recording might require 10 minutes, and the temperature/humidity data transmitted may vary. The temperature data might be in °C instead of °F.

Wittime WT2022A wireless hygro thermo.zip (24.7 KB)

Filename	Description
Wittime_Ch1_78.4F_53RH.sub	Channel 1: 78.4°F, 53% relative humidity
Wittime_Ch1_78.6F_53RH.sub	Channel 1: 78.6°F, 53% relative humidity
Wittime_Ch1_80.6F_66RH.sub	Channel 1: 80.6°F, 66% relative humidity
Wittime_Ch1_80.7F_66RH.sub	Channel 1: 80.7°F, 66% relative humidity
Wittime_Ch1_80.9F_66RH.sub	Channel 1: 80.9°F, 66% relative humidity
Wittime_Ch1_81.1F_67RH.sub	Channel 1: 81.1°F, 67% relative humidity
Wittime_Ch2_78.9F_55RH.sub	Channel 2: 78.9°F, 55% relative humidity
Wittime_Ch2_78.9F_56RH.sub	Channel 2: 78.9°F, 56% relative humidity
Wittime_Ch3_79.1F_60RH.sub	Channel 3: 79.1°F, 60% relative humidity
Wittime_Ch3_79.7F_55RH.sub	Channel 3: 79.7°F, 55% relative humidity

Photos

Transmitter back cover with FCC ID

[SkorP]

came today

I’ll take it apart tomorrow

[digitalcircuit]

Awesome, thank you! If/when desired, I’m happy to help with testing or providing additional recordings.

(Meanwhile, I’ve also gotten an ecobee thermostat from my utility provider with its own WR91881541520 920-927.35 MHz wireless Smart Sensors providing temperature and motion sensing. I’ll see about filing a new post for those.)

[oleksiikutuzov]

Your devices are looking pretty much like my inFactory NC-3982-675 sensor.

Attaching RAW recordings of 10 transmissions done with manual TX button for 3 channels. All should transmit 23.0 degrees C and 49% humidity as in the photo.

Infactory_ch1.sub (98.7 KB)
Infactory_ch2.sub (114.7 KB)
Infactory_ch3.sub (129.5 KB)

Mine is parsed fine with the following decoder:

merbanan/rtl_433/blob/master/src/devices/infactory.c

[SkorP]

assembly leaves a lot to be desired

[Spildit]

This is interesting … :

rtl_433/src/devices at master · merbanan/rtl_433

Wouldn’t it be possible to “adapt” those parsers to work with flipper ? It would save time and money in devices if somehow those could be added to the SD card to parse flipper Sub-Ghz protocols … It would increase the capability of Flipper to know more signal types without the need of analyzing all those protocols one by one ???

[SkorP]

Flipper WS

[Spildit]

Very, Very cool ! Hope that this will end up implemented on the official firmware !!! Also related request …

Eltek (GD-10) dataloggers:

Hopefully someone will be able to take a look at this at some point in the future … It would be nice to have this implemented on flipper.

[digitalcircuit]

Awesome work!

Early tests

I gave a local build of the current latest commit 1df29b7 a test, but nothing shows up. I suspect the protocol Wittime uses in the WT2022A is modified in some way, perhaps to avoid overlap with other sensors. Older Wittime product lines do have the inFactory style remote sensor with LCD display (e.g. the Wittime 2081).

No rush from me, just offering early feedback.

Dew point

It might be worthwhile adding dew point calculation. The Wittime base stations (and others) have this, which makes it much easier to compare absolute humidity, e.g. “is opening a window going to improve my humidity situation.”

Please just show us the dew points, digital thermometer companies. - Dennis...

There’s a simple approximation which should work well enough:

Td = T - ((100 - RH)/5.)
where Td is dew point temperature (in degrees Celsius), T is observed temperature (in degrees Celsius), and RH is relative humidity (in percent). Apparently this relationship is fairly accurate for relative humidity values above 50%.

[Spildit]

@digitalcircuit , your station is a Wittime while the protocol/station that @SkorP implemented/have is a Newentor / Infactory so it’s natural that Flipper doesn’t pick your Wittime with infactory code …

[SkorP]

WeatherStation

check plz

[SkorP]

[Spildit]

Looks very cool ! I don’t have a inFactory to test but looks great. I would ask for an encoder as well so one could send spoofed sensor data back to the console/monitor screen of the station…
Regards and nice work !

[SkorP]

uh no, ourselves, we are good) the algorithm of action is this, in 1 screen ALL new sensors and protocols are added as they are received. when you receive data again in the same sensor, the data is updated. you can select the desired sensor from the list and open it. the data will be updated as it is received, and even if you open any sensor, the flipper continues to listen to the air and update the data in the required fields

[Spildit]

I was asking for FLIPPER to ACT AS a SENSOR so it would send fake/spoofed data to the console of the meteorologic station…

[SkorP]

try now, added your protocol

[digitalcircuit]

Working great!

All three channels of my Wittime WT2022A sensors are picked up and the measurements match what my Wittime 2076B weather station shows:

NOTE: I’ve set the Wittime display to low brightness for night time. It’s usually easier to read in person.

It’s really nice that it continues to update in real-time, even with the sensor detail display open. I initially thought that wouldn’t work because it stopped blinking the cyan RX notification sequence, however, it still blinks the green RX decoded sequence in detail view.

Potential future improvements

• Using the Left/Right arrows when showing a sensor reading to switch between sensors
  • The channel number isn’t visible in the list view, so it can be difficult to tell which sensor I’m selecting
• A setting for Fahrenheit or Celsius
• A setting for humidity percentage (relative) or dew point (absolute)

But these changes aren’t necessary for shipping this. Thank you for implementing the Weather Station app!

[SkorP]

celsius fahrenheit will be hotter when we decide how to store user files, but you can think about the arrows

[Spildit]

Very cool !!! Installed it today and i like it. I still ask for storing the data and send it back / encoder / so we can mess with the data shown on the display of the station !!!

[Spildit]

Also it would be cool to have an option to import/decode a raw file with WS content …