Appendix B: 1-Wire® Communications Examples - iButtonLink LINK 12 User Manual

A B: 1-Wire® Communications Examples
PPENDIX
The sequence for reading a DS18B20 temperature sensor via a LINK device is:
1. Issue a 1-Wire® reset using " r "
2. Enter byte mode using " b " (in pull-up mode if supported by device " p ") and address
the ROM by sending " 0x55 " followed by the ROM address in reverse byte order
a. For the LinkHub-S and the LinkHub-E, send " 55 " followed by the ROM
address in reverse byte order
i. Example: if the discovered ID is " E60000003DA0E128 ", you would
3. Send the convert command " 44 " and exit byte mode <CR>
4. Wait at least 900 ms for the conversion to complete, then issue a 1-Wire® reset " r "
5. Enter byte mode using " b " and address the ROM as before
6. Send the read command of " BE "
a. For The LinkHub-S, The LinkHub-E, and The LinkOEM, send the read
command of " BE "
7. Send two read commands as " FFFF ". The echoed/returned data will contain the
temperature reading in Intel (little-endian) order as a 16 bit signal integer (may be
formatted as four hex characters)
8. Exit byte mode <CR>
E :
XAMPLE
The returned value will be in 1/16 degree Celsius increments. A return value of 5701 represents
0x0157, or 343 in decimal. Dividing by 16 gives you 21.4
Mind the sign bit, or values below freezing will appear to be unusually warm by several
thousand degrees.
D H :
EBUGGING INT
The power-up default of the 18B20 is 85°C (185°F). If you receive this value, it might indicate
that this device has never executed a convert. It is possible to address an 18B20 and NOT have
enough power available for it to execute a convert.
address it as " 28E1A03D000000E6 "
The LINK™ Family Manual
Version 1.6 ©iButtonLink, LLC 2016
C (70.6 F).
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