File : CS-SUP-MUTI-WTHERMAPP-E01.sxw
5 INFORMATION RELATIVE TO THE PROBES ASSOCIATED WITH THE
WAVETHERM MODULES
5.1 DALLAS Probes
5.1.1 Coding of temperatures for the DALLAS probe type DS18B20
These probes have a resolution of 12 bits and their value is coded on two bytes (MSB first)
Negative values are expressed in two's complements with addition of a sign.
MSB
LSB
MSB
LSB
Most Significant Byte
Leasr Significant Byte
b7
b6
b5
b4
b3
b2
b1
b0
b7
b6
b5
b4
b3
b2
b1
b0
S
S
S
S
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
2
-1
2
-2
2
-3
2
-4
Unit : Celsius degree (°C)
Bits [b7:b3] : sign bit.
Remark:
The hexadecimal value 0x4FFF indicates the absence of a probe, or a connection error between
the module and the probe.
Some temperature values:
Temperature
Binary value (MSB First)
Hexadecimal value
+125°C
0000
0111
1101
0000
0x07D0
+85°C
0000
0101
0101
0000
0x0550
+25°C
0000
0001
1001
0000
0x0190
0°C
0000
0000
0000
0000
0x0000
-10.125°C
1111
1111
0101
1110
0xFF5E
-55°C
1111
1100
1001
0000
0xFC90
5.1.2 Probe ID
The probe ID corresponds to a unique code attributed to each DALLAS temperature probe in the factory.
This code is composed of 8 bytes defined as follows:
MSByte
LSByte
1 byte
6 bytes
1 byte
Family Code
Serial n° (48 bits)
CRC Code
The family code is used to distinguish between the probes used:
Probe DS18S20 : 0x10
Probe DS18B20 : 0x28
WaveTherm modules – application handbook
page 15 of 65
