Protocol of the Lacrosse TX3-TH thermo/hygro sensor

Compatible: TX4, et certainly others...

Each frame is 44 bits long. It is composed of:

Example 1
00001010000000001110011100110001011100111101

Example 2
00001010111011001100011000000000011000001100

Example 3
00001010000001000100011100100011011100100111

Example 4
00001010111000001111010100100000010100100101

Example 5
00001010111000000000111000000110011100000011

Example 6
00001010000010000100011010000001011010000011

The active values of the frames are explained below:

Example 1
0000 1010 0000 0000 1110 0111 0011 0001 0111 0011 1101
0 A 0 0 70 7 3 1 7 3 D 
Checksum: (0 + A + 0 + 0 + E + 7 + 3 + 1 + 7 + 3) and F = D D

Example 2
0000 1010 1110 1100 1100 0110 0000 0000 0110 0000 1100
0 A E C 60 6 0 0 6 0 C 
Checksum: (0 + A + E + C + C + 6 + 0 + 0 + 6 + 0) and F = C C

Example 3
0000 1010 0000 0100 0100 0111 0010 0011 0111 0010 0111
0 A 0 4 20 7 2 3 7 2 7 
Checksum: (0 + A + 0 + 4 + 4 + 7 + 2 + 3 + 7 + 2) and F = 7 7

Example 4
0000 1010 1110 0000 1111 0101 0010 0000 0101 0010 0101
0 A E 0 71 5 2 0 5 2 5 
Checksum: (0 + A + E + 0 + F + 5 + 2 + 0 + 5 + 2) and F = 5 5

Example 5
0000 1010 1110 0000 0000 1110 0000 0110 0111 0000 0011
0 A E 0 00 E 0 6 7 0 3 
Checksum: (0 + A + E + 0 + 0 + E + 0 + 6 + 7 + 0) and F = 3 3

Example 6
0000 1010 0000 1000 0100 0110 1000 0001 0110 1000 0011
0 A 0 8 20 6 8 1 6 8 3 
Checksum: (0 + A + 0 + 8 + 4 + 6 + 8 + 1 + 6 + 8) and F = 3 3

 Start sequence
 Sensor type
 Sensor Address
 Parity check
 Data values
 Redundancy values
 Checksum

The measure is on 3 BCD digits, the two first digits are repeated to fill the 5 nibles.

The parity shall be equal to zero and is the exclusive or of the parity bit and the bits of the three data nibbles

For temperature, an offset of 50 deg has to be substracted from the measure.

  1. address : 07 - Parity OK - [tempe] 23.1 deg
  2. address : 66 - Parity OK - [hygro] 60.0 %
  3. address : 22 - Parity OK - [tempe] 22.3 deg
  4. address : 07 - Parity OK - [hygro] 52.0 %
  5. address : 00 - Parity NOK - [hygro] E0.6 %
  6. address : 42 - Parity OK - [tempe] 18.1 deg

Thanks to Matthias for the purple bit information.

I am interested by any comment or more information on the format of these frames. Contact: Jean-Paul ROUBELAT - F6FBB

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