Decoding Lacrosse TX141TH-B Temperature Humidity Sensor 433MHz

uhu1 · April 2, 2016, 6:42am

I found this to be a good starting point: decoded LaCrosse TX2U temperature sensor 433MHz - Networking, Protocols, and Devices - Arduino Forum for both inspiration and measurement technique. The Serial Monitor changes too fast to be useful, but the Serial Plotter is great.

It appears that every minute, 6 identical packages are transmitted. Each package is 44 bits long. There are 3 types of bits:

H (header bits), consisting of pulses of 950us followed by delays of 1650us;
0 (zeros), pulses of 300 us followed by delays of 700us;
1 (ones), pulses of 500 us followed by delays of 700us.

(pulse duration and delay are somewhat variable around the values above).

The protocol seems to be:

Bits 0-3: header
Bits 4-11: device ID, changes when replacing the batteries. Unlike in the post linked above, bit 11 does not appear to be a checksum.
Bits 12-15: either 1111 for automatic transmission (once every 60 seconds) or 1011 for manual transmission (using the button in the battery compartment). Manual transmission does not update the weather station.
Bits 16-27: encode the temperature. The system of encoding decimal digits seems to be ditched in favor of a more elegant one: apply a NOT (change 1 to 0 and 0 to 1), convert to base 10, divide by 10 (into a float), subtract 50, and the result is the temperature in C.
Bits 28-35: encode the relative humidity. Apply a NOT, convert to base 10, and the result is the relative humidity in %.
Bits 36-43: appear to encode a checksum (though I plan to double-check if this is not the dew point, also reported by the weather station).

Example:
HHHH 1000 0010 1111 1101 0010 1111 1101 0011 1010 0100
encoding T=22.0C and RH=44%

Attached, a slightly improved version of the raw dump from the link above.

dump_433_mhz.ino (790 Bytes)

uhu1 · April 4, 2016, 10:05pm

If someone feels like cracking the checksum, here is a text dump with transmissions. 0, 1 are bits. 2 are long header signals. The final bit vs. header might be a bug, although it appears reproducible.

ID=125	T=23.30	RH=44 2222 1000 0010 1011 1101 0010 0010 1101 0011 0111 1002
ID=182	T=21.30	RH=47 2222 0100 1001 1111 1101 0011 0110 1101 0000 0011 0002
ID=125	T=23.30	RH=44 2222 1000 0010 1111 1101 0010 0010 1101 0011 1001 1002
ID=182	T=21.30	RH=47 2222 0100 1001 1111 1101 0011 0110 1101 0000 0011 0002
ID=125	T=23.30	RH=44 2222 1000 0010 1111 1101 0010 0010 1101 0011 1001 1002
ID=182	T=21.30	RH=47 2222 0100 1001 1011 1101 0011 0110 1101 0000 1101 0002
ID=125	T=23.30	RH=43 2222 1000 0010 1111 1101 0010 0010 1101 0100 0011 0111
ID=179	T=21.60	RH=49 2222 0100 1100 1111 1101 0011 0011 1100 1110 1001 0002
ID=125	T=23.20	RH=43 2222 1000 0010 1111 1101 0010 0011 1101 0100 0111 0002
ID=179	T=22.40	RH=49 2222 0100 1100 1111 1101 0010 1011 1100 1110 0110 0112
ID=125	T=23.10	RH=44 2222 1000 0010 1111 1101 0010 0100 1101 0011 0011 1100
ID=179	T=22.70	RH=48 2222 0100 1100 1111 1101 0010 1000 1100 1111 0101 1002
ID=125	T=23.00	RH=44 2222 1000 0010 1111 1101 0010 0101 1101 0011 0111 1011
ID=179	T=22.90	RH=47 2222 0100 1100 1111 1101 0010 0110 1101 0000 0101 1002
ID=125	T=23.00	RH=44 2222 1000 0010 1111 1101 0010 0101 1101 0011 0111 1011
ID=125	T=23.00	RH=44 2222 1000 0010 1011 1101 0010 0101 1101 0011 1001 1011
ID=179	T=23.00	RH=47 2222 0100 1100 1111 1101 0010 0101 1101 0000 1001 0012
ID=179	T=23.00	RH=47 2222 0100 1100 1011 1101 0010 0101 1101 0000 0111 0012
ID=125	T=23.10	RH=44 2222 1000 0010 1011 1101 0010 0100 1101 0011 1101 1100
ID=179	T=23.00	RH=46 2222 0100 1100 1111 1101 0010 0101 1101 0001 0110 0112
ID=179	T=23.00	RH=46 2222 0100 1100 1111 1101 0010 0101 1101 0001 0110 0112
ID=125	T=23.10	RH=44 2222 1000 0010 1111 1101 0010 0100 1101 0011 0011 1100
ID=179	T=23.00	RH=46 2222 0100 1100 1111 1101 0010 0101 1101 0001 0110 0112
ID=125	T=23.10	RH=44 2222 1000 0010 1111 1101 0010 0100 1101 0011 0011 1100
ID=179	T=23.00	RH=46 2222 0100 1100 1111 1101 0010 0101 1101 0001 0110 0112
ID=179	T=23.00	RH=45 2222 0100 1100 1111 1101 0010 0101 1101 0010 0100 1010
ID=179	T=23.00	RH=45 2222 0100 1100 1111 1101 0010 0101 1101 0010 0100 1010
ID=125	T=22.90	RH=43 2222 1000 0010 1111 1101 0010 0110 1101 0100 0001 1111
ID=179	T=23.00	RH=45 2222 0100 1100 1111 1101 0010 0101 1101 0010 0100 1010
ID=179	T=22.90	RH=45 2222 0100 1100 1111 1101 0010 0110 1101 0010 1000 0001
ID=179	T=22.90	RH=45 2222 0100 1100 1111 1101 0010 0110 1101 0010 1000 0001
ID=125	T=22.80	RH=43 2222 1000 0010 1111 1101 0010 0111 1101 0100 0101 1000
ID=179	T=22.90	RH=45 2222 0100 1100 1111 1101 0010 0110 1101 0010 1000 0001
ID=125	T=22.70	RH=43 2222 1000 0010 1111 1101 0010 1000 1101 0100 1110 1002
ID=179	T=22.90	RH=45 2222 0100 1100 1111 1101 0010 0110 1101 0010 1000 0001
ID=125	T=22.70	RH=43 2222 1000 0010 1111 1101 0010 1000 1101 0100 1110 1002
ID=179	T=22.80	RH=45 2222 0100 1100 1111 1101 0010 0111 1101 0010 1100 0111
ID=125	T=22.70	RH=43 2222 1000 0010 1111 1101 0010 1000 1101 0100 1110 1002
ID=125	T=22.60	RH=43 2222 1000 0010 1111 1101 0010 1001 1101 0100 1010 1111
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0010
ID=125	T=22.60	RH=43 2222 1000 0010 1111 1101 0010 1001 1101 0100 1010 1111
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0010
ID=125	T=22.50	RH=43 2222 1000 0010 1111 1101 0010 1010 1101 0100 0110 0102
ID=125	T=22.60	RH=43 2222 1000 0010 1111 1101 0010 1001 1101 0100 1010 1111
ID=125	T=22.60	RH=43 2222 1000 0010 1111 1101 0010 1001 1101 0100 1010 1111
ID=179	T=23.00	RH=45 2222 0100 1100 1111 1101 0010 0101 1101 0010 0100 1011
ID=125	T=22.60	RH=43 2222 1000 0010 1111 1101 0010 1001 1101 0100 1010 1111
ID=179	T=23.00	RH=46 2222 0100 1100 1111 1101 0010 0101 1101 0001 0110 0112
ID=125	T=22.60	RH=43 2222 1000 0010 1111 1101 0010 1001 1101 0100 1010 1111
ID=179	T=23.10	RH=45 2222 0100 1100 1111 1101 0010 0100 1101 0010 0000 1100
ID=125	T=22.50	RH=43 2222 1000 0010 1111 1101 0010 1010 1101 0100 0110 0102
ID=179	T=23.10	RH=45 2222 0100 1100 1111 1101 0010 0100 1101 0010 0000 1101
ID=125	T=22.50	RH=43 2222 1000 0010 1111 1101 0010 1010 1101 0100 0110 0102
ID=125	T=22.50	RH=43 2222 1000 0010 1111 1101 0010 1010 1101 0100 0110 0102
ID=125	T=22.50	RH=43 2222 1000 0010 1111 1101 0010 1010 1101 0100 0110 0102
ID=179	T=23.00	RH=45 2222 0100 1100 1111 1101 0010 0101 1101 0010 0100 1011
ID=125	T=22.50	RH=43 2222 1000 0010 1111 1101 0010 1010 1101 0100 0110 0102
ID=179	T=23.00	RH=45 2222 0100 1100 1111 1101 0010 0101 1101 0010 0100 1010
ID=125	T=22.50	RH=43 2222 1000 0010 1111 1101 0010 1010 1101 0100 0110 0102
ID=179	T=23.00	RH=44 2222 0100 1100 1111 1101 0010 0101 1101 0011 1011 1110
ID=125	T=22.40	RH=43 2222 1000 0010 1111 1101 0010 1011 1101 0100 0010 0012
ID=179	T=22.90	RH=44 2222 0100 1100 1111 1101 0010 0110 1101 0011 0111 0101
ID=125	T=22.40	RH=43 2222 1000 0010 1111 1101 0010 1011 1101 0100 0010 0011
ID=179	T=22.90	RH=44 2222 0100 1100 1111 1101 0010 0110 1101 0011 0111 0101
ID=125	T=22.40	RH=43 2222 1000 0010 1111 1101 0010 1011 1101 0100 0010 0011
ID=179	T=22.90	RH=44 2222 0100 1100 1111 1101 0010 0110 1101 0011 0111 0100
ID=125	T=22.40	RH=43 2222 1000 0010 1111 1101 0010 1011 1101 0100 0010 0012
ID=179	T=22.90	RH=44 2222 0100 1100 1111 1101 0010 0110 1101 0011 0111 0101
ID=125	T=22.40	RH=43 2222 1000 0010 1111 1101 0010 1011 1101 0100 0010 0011
ID=125	T=22.40	RH=43 2222 1000 0010 1111 1101 0010 1011 1101 0100 0010 0011
ID=125	T=22.40	RH=43 2222 1000 0010 1111 1101 0010 1011 1101 0100 0010 0011
ID=179	T=22.90	RH=44 2222 0100 1100 1111 1101 0010 0110 1101 0011 0111 0101
ID=125	T=22.30	RH=43 2222 1000 0010 1111 1101 0010 1100 1101 0100 1100 0000
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=125	T=22.30	RH=43 2222 1000 0010 1111 1101 0010 1100 1101 0100 1100 0000
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0010
ID=125	T=22.30	RH=43 2222 1000 0010 1111 1101 0010 1100 1101 0100 1100 0000
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=125	T=22.30	RH=43 2222 1000 0010 1111 1101 0010 1100 1101 0100 1100 0000
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0010
ID=125	T=22.30	RH=43 2222 1000 0010 1111 1101 0010 1100 1101 0100 1100 0000
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=125	T=22.20	RH=43 2222 1000 0010 1111 1101 0010 1101 1101 0100 1000 0111
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=125	T=22.30	RH=43 2222 1000 0010 1111 1101 0010 1100 1101 0100 1100 0000
ID=125	T=22.20	RH=43 2222 1000 0010 1111 1101 0010 1101 1101 0100 1000 0111
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0010
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=125	T=22.20	RH=43 2222 1000 0010 1111 1101 0010 1101 1101 0100 1000 0110

uhu1 · April 4, 2016, 11:43pm

More:

ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=125	T=22.20	RH=43 2222 1000 0010 1111 1101 0010 1101 1101 0100 1000 0110
ID=125	T=22.20	RH=43 2222 1000 0010 1111 1101 0010 1101 1101 0100 1000 0111
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=125	T=22.20	RH=43 2222 1000 0010 1111 1101 0010 1101 1101 0100 1000 0110
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0010
ID=125	T=22.20	RH=43 2222 1000 0010 1111 1101 0010 1101 1101 0100 1000 0111
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=125	T=22.10	RH=44 2222 1000 0010 1111 1101 0010 1110 1101 0011 1110 0011
ID=125	T=22.10	RH=44 2222 1000 0010 1111 1101 0010 1110 1101 0011 1110 0011
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=125	T=22.10	RH=44 2222 1000 0010 1111 1101 0010 1110 1101 0011 1110 0011
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=125	T=22.10	RH=44 2222 1000 0010 1111 1101 0010 1110 1101 0011 1110 0011
ID=179	T=22.80	RH=44 2222 0100 1100 1111 1101 0010 0111 1101 0011 0011 0011
ID=125	T=22.10	RH=44 2222 1000 0010 1111 1101 0010 1110 1101 0011 1110 0011
ID=179	T=22.80	RH=43 2222 0100 1100 1111 1101 0010 0111 1101 0100 1001 1101
ID=125	T=22.10	RH=44 2222 1000 0010 1111 1101 0010 1110 1101 0011 1110 0011
ID=179	T=22.70	RH=43 2222 0100 1100 1111 1101 0010 1000 1101 0100 0010 1102
ID=125	T=22.10	RH=44 2222 1000 0010 1111 1101 0010 1110 1101 0011 1110 0011
ID=179	T=22.70	RH=43 2222 0100 1100 1111 1101 0010 1000 1101 0100 0010 1102
ID=179	T=22.70	RH=43 2222 0100 1100 1111 1101 0010 1000 1101 0100 0010 1102
ID=125	T=22.00	RH=44 2222 1000 0010 1111 1101 0010 1111 1101 0011 1010 0100
ID=179	T=22.60	RH=43 2222 0100 1100 1111 1101 0010 1001 1101 0100 0110 1012
ID=125	T=22.00	RH=44 2222 1000 0010 1111 1101 0010 1111 1101 0011 1010 0100
ID=179	T=22.60	RH=43 2222 0100 1100 1111 1101 0010 1001 1101 0100 0110 1012
ID=125	T=22.00	RH=44 2222 1000 0010 1111 1101 0010 1111 1101 0011 1010 0100
ID=179	T=22.60	RH=43 2222 0100 1100 1111 1101 0010 1001 1101 0100 0110 1012
ID=125	T=21.90	RH=44 2222 1000 0010 1111 1101 0011 0000 1101 0011 1011 0002
ID=179	T=22.60	RH=43 2222 0100 1100 1111 1101 0010 1001 1101 0100 0110 1012
ID=125	T=21.90	RH=44 2222 1000 0010 1111 1101 0011 0000 1101 0011 1011 0002
ID=179	T=22.60	RH=43 2222 0100 1100 1111 1101 0010 1001 1101 0100 0110 1012
ID=125	T=21.90	RH=44 2222 1000 0010 1111 1101 0011 0000 1101 0011 1011 0001
ID=179	T=22.50	RH=43 2222 0100 1100 1111 1101 0010 1010 1101 0100 1010 0002
ID=125	T=21.90	RH=44 2222 1000 0010 1111 1101 0011 0000 1101 0011 1011 0002
ID=179	T=22.60	RH=43 2222 0100 1100 1111 1101 0010 1001 1101 0100 0110 1012
ID=125	T=21.90	RH=44 2222 1000 0010 1111 1101 0011 0000 1101 0011 1011 0002
ID=179	T=22.60	RH=44 2222 0100 1100 1111 1101 0010 1001 1101 0011 1100 0102
ID=125	T=21.90	RH=44 2222 1000 0010 1111 1101 0011 0000 1101 0011 1011 0002
ID=179	T=22.60	RH=44 2222 0100 1100 1111 1101 0010 1001 1101 0011 1100 0102
ID=125	T=21.90	RH=44 2222 1000 0010 1111 1101 0011 0000 1101 0011 1011 0002
ID=179	T=22.60	RH=44 2222 0100 1100 1111 1101 0010 1001 1101 0011 1100 0102
ID=125	T=21.80	RH=44 2222 1000 0010 1111 1101 0011 0001 1101 0011 1111 0112
ID=179	T=22.50	RH=44 2222 0100 1100 1111 1101 0010 1010 1101 0011 0000 1112
ID=125	T=21.80	RH=44 2222 1000 0010 1111 1101 0011 0001 1101 0011 1111 0112
ID=179	T=22.50	RH=44 2222 0100 1100 1111 1101 0010 1010 1101 0011 0000 1112
ID=125	T=21.80	RH=44 2222 1000 0010 1111 1101 0011 0001 1101 0011 1111 0112
ID=179	T=22.50	RH=44 2222 0100 1100 1111 1101 0010 1010 1101 0011 0000 1112
ID=125	T=21.80	RH=44 2222 1000 0010 1111 1101 0011 0001 1101 0011 1111 0112
ID=179	T=22.40	RH=44 2222 0100 1100 1111 1101 0010 1011 1101 0011 0100 1002
ID=125	T=21.80	RH=44 2222 1000 0010 1111 1101 0011 0001 1101 0011 1111 0112
ID=179	T=22.40	RH=44 2222 0100 1100 1111 1101 0010 1011 1101 0011 0100 1002
ID=125	T=21.80	RH=44 2222 1000 0010 1111 1101 0011 0001 1101 0011 1111 0112
ID=179	T=22.40	RH=44 2222 0100 1100 1111 1101 0010 1011 1101 0011 0100 1002
ID=125	T=21.80	RH=44 2222 1000 0010 1111 1101 0011 0001 1101 0011 1111 0111
ID=179	T=22.40	RH=44 2222 0100 1100 1111 1101 0010 1011 1101 0011 0100 1002
ID=125	T=21.80	RH=44 2222 1000 0010 1111 1101 0011 0001 1101 0011 1111 0112
ID=179	T=22.40	RH=44 2222 0100 1100 1111 1101 0010 1011 1101 0011 0100 1002
ID=125	T=21.70	RH=44 2222 1000 0010 1111 1101 0011 0010 1101 0011 0011 1101
ID=125	T=21.70	RH=44 2222 1000 0010 1111 1101 0011 0010 1101 0011 0011 1102
ID=179	T=22.40	RH=44 2222 0100 1100 1111 1101 0010 1011 1101 0011 0100 1002
ID=125	T=21.70	RH=44 2222 1000 0010 1111 1101 0011 0010 1101 0011 0011 1102
ID=179	T=22.60	RH=44 2222 0100 1100 1111 1101 0010 1001 1101 0011 1100 0102
ID=125	T=21.70	RH=44 2222 1000 0010 1111 1101 0011 0010 1101 0011 0011 1102
ID=179	T=22.90	RH=44 2222 0100 1100 1111 1101 0010 0110 1101 0011 0111 0100
ID=125	T=21.70	RH=44 2222 1000 0010 1111 1101 0011 0010 1101 0011 0011 1101
ID=179	T=23.20	RH=43 2222 0100 1100 1111 1101 0010 0011 1101 0100 1011 0102
ID=125	T=21.70	RH=44 2222 1000 0010 1111 1101 0011 0010 1101 0011 0011 1102
ID=179	T=23.50	RH=43 2222 0100 1100 1111 1101 0010 0000 1101 0100 0111 1112
ID=125	T=21.70	RH=44 2222 1000 0010 1111 1101 0011 0010 1101 0011 0011 1102
ID=179	T=23.60	RH=43 2222 0100 1100 1111 1101 0001 1111 1101 0100 0001 0012

uhu1 · April 8, 2016, 8:15pm

I just got my hands on a La Crosse TX141TH-BV2 sensor. As far as I can tell, it uses the same encoding.

shmish · February 14, 2017, 12:19am

Hi Uhul, perhaps you'll get notified about a response to this hold thread.
I downloaded and tried out your sketch with my TX7UN sensor. All I get in the serial monitor is:

The serial plotter plots two horizontal lines for 0 and 2000.

I have put an audio card oscilliscope on my 433MHz receiver and received a signal shown in the attached picture. I'm wondering if you have any ideas on what's going on with the arduino serial print?

thierrycc · December 31, 2018, 8:36pm

TX141TH-BV2 sensor

Hi Uhul, perhaps you'll get notified about this old post.

I will try to read the TX141TH-BV2 sensor but i don't get your result.
Do you have any advice for me ?

thierrycc · December 31, 2018, 9:57pm

tuppi-ovh · November 2, 2019, 3:59pm

Hello,

For the checksum calculation please refer to my site: Compatibility Link 1 -.

Regards

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