fphammerle/tchibo-287717-weather-station-signal

Tchibo 287717 Wireless Thermometer/Hygrometer Signal Decoding

Tchibo 287717 Weather Station Signal Decoding

Product Details

• Name: Tchibo Funk-Wetterstation
• Model: 287717
• Frequency (indicated): 434 MHz
• Powered by two 1.5V AAA batteries
• Contains thermometer and hygrometer

Signal

Sensor transmits an OOK-modulated 1-second-long signal approximately once every 5 minutes on 433.85 MHz.

Recorded with gqrx via RTL2832U/R820T (433.79 MHz, AM):

After conversion to binary signal:

Decoding

Signal has a pulse distance encoding.

Each transmission contains 6 repeats of the same message.

Each messages consists of 42 bits.

Low-bits have a pause length of approximately 1.5ms, high-bits 3.5ms:

Greatest common divisor:

We recorded a few transmissions (recordings/*.wav) and compared the received data with the values indicated on the display (displayed-values.yml).

bit range	carried information
0-9	constant, maybe sensor address?
10-13	unknown
14-25	temperature
26-33	relative humidity
34-42	probably checksum

Humidity

bit index	26	27	28	29	30	31	32	33
bit value	8	4	2	1	128	64	32	16

Provides the relative humidity in percent.

Temperature

bit index	14	15	16	17	18	19	20	21	22	23	24	25
bit value	8	4	2	1	128	64	32	16	2048	1024	512	256

Linear regression model estimates temperature_celsius = temperature_index * 0.055601938800118336 - 67.83753671810342.