Protocol of the Lacrosse WS7000-27/28 meteo sensor

Each frame is 46 bits long. It is composed of:

• 10bits of 0 (start sequence) [blue]
• 7 blocks of four bits separated by a bit 1 [red] to be checked and skipped

When extracting data from the examples, we get:
Example 1

0

0

0

0

0

1

1

0

1

0

1

0

0

0

0

1

1

0

0

0

0

1

0

1

1

1

0

0

Example 2

0

0

0

0

0

1

1

0

1

1

1

0

0

1

0

0

1

0

0

0

0

1

0

0

1

1

1

0

Example 3

0

0

0

0

0

1

1

1

1

1

1

0

0

1

0

0

1

0

0

0

0

1

0

1

1

1

1

0

The 1st bit of each word is LSB, so we have to reverse the 4 bits of each word.

The active values of the sensor is coloured in [green] in the following tables:
Example 1

0	0	0	0		0	1	1	0		0	1	0	1		1	0	0	0		0	0	0	1		1	0	1	0		0	0	1	1
0					+	6				5					8					1					A					3
Check Xor : (0 ^ 6 ^ 5 ^ 8 ^ 1 ^ A) = 0 Check Sum : (const5 + 0 + 6 + 5 + 8 + 1 + A) and F = 3

Example 2

0	0	0	0		0	1	1	0		0	1	1	1		0	0	1	0		0	0	0	1		0	0	1	0		0	1	1	1
0					+	6				7					2					1					2					7
Check Xor : (0 ^ 6 ^ 7 ^ 2 ^ 1 ^ 2) = 0 Check Sum : (const5 + 0 + 6 + 7 + 2 + 1 + 2) and F = 7

Example 3

0	0	0	0		1	1	1	0		0	1	1	1		0	0	1	0		0	0	0	1		1	0	1	0		0	1	1	1
0					-	6				7					2					1					A					7
Check Xor : (0 ^ E ^ 7 ^ 2 ^ 1 ^ A) = 0 Check Sum : (const5 + 0 + E + 7 + 2 + 1 + A) and F = 7

	Sensor type is 0
	Temperature is positive
	Sensor Address
	Data values
	CheckXor
	Checksum

The first block is the LSB, so the values are repectively:

1. [temp] 18.5 deg
2. [temp] 12.7 deg
3. [temp] -12.7 deg

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

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