Digi XBee - Page 187

API Operation Frame descriptions
XBee/XBee-PRO® S2C ZigBee® RF Module
187
AD0 = 0x0002
AD1 = 0x00CE
AD2 = 0x00EA
AD3 = 0x0052
T = 0x016A
To convert these to temperature and humidity values, the following equations should be used.
Temperature (°C) = (T / 16), for T < 2048
= - (T & 0x7FF) / 16, for T >= 2048
Vsupply = (AD2 * 5.1) / 255
Voutput = (AD3 * 5.1) / 255
Relative Humidity = ((Voutput / Vsupply) - 0.16) / (0.0062)
True Humidity = Relative Humidity / (1.0546 - (0.00216 * Temperature (°C))) Looking at the sample
data, we have:
Vsupply = (234 * 5.1 / 255) = 4.68
Voutput = (82 * 5.1 / 255) = 1.64 Temperature = (362 / 16) = 22.625°C
Relative H = (161.2903 * ((1.64/4.68) - 0.16)) = 161.2903 * (0.19043) = 30.71%
True H = (30.71 / (1.0546 - (0.00216 * 22.625))) = (30.71 / 1.00573) = 30.54%
Frame fields Offset Example
Start delimiter 0 0x7E
Length MSB 1 0x00
LSB 2 0x17
Frame type 3 0x94
64-bit source address MSB 4 0x00
5 0x13
6 0xA2
7 0x00
8 0x40
9 0x52
10 0x2B
LSB 11 0xAA
16-bit source network address MSB 12 0xDD
LSB 13 0x6C
Receive options 14 0x01
1-Wire sensors
15 0x03