1-wire

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rough draft

The 1-wire network is a communications bus system designed by someone(?) at Dallas Semiconductor (now part of Maxim Integrated) that provides low-speed data, signaling, and power, using up a total of one pin on the CPU no matter how many peripheral chips are on that bus. (Other ways of connecting a peripheral to the CPU either require another pin for each peripheral, or require more pins for the first peripheral, or both).

The 1-wire network is perhaps the most popular way to measure temperatures at many different locations and send that data back to one central processor.


Media: A Guide to the 1WRJ45 Standard.pdf

It makes it easier to troubleshoot if each PCB has 2 RJ45 connectors (or a dual RJ45 connector), with 1 LED indicating power and 1 LED indicating 1-wire signals.

For clarity each of the 8 wires from the standard 1WRJ45 connector may be labeled with the following 2-letter PCB silkscreen abbreviation:

 1 5R (VCC return)
 2 +5 (VCC power)
 3 AR (Analog return) (?)
 4 OW (one-wire I/O)
 5 OR (one-wire return)
 6 AS (Analog signal) (?)
 7 +V (V raw power)
 8 VR (V raw return)

Further reading

Wikipedia: 1-Wire

Bich Pham. "One-Wire Serial Bus Carries Isolated Power And Data". http://electronicdesign.com/power/one-wire-serial-bus-carries-isolated-power-and-data The same circuit is also shown in "APPLICATION NOTE 3754: Single-Wire Serial Bus Carries Isolated Power and Data" http://www.maximintegrated.com/app-notes/index.mvp/id/3754 uses a MAX845 transformer driver and a transformer to send power and data from the host to the parasitic-power 1-wire device, and an optocoupler to send data from the 1-wire device back to the host.

  • 1-Wire File System (OWFS): http://owfs.org/
    • has more information on 1-wire bus wiring standards using RJ-11 or RJ45 connectors.[1]


Is it true that "IEEE 1451.4 uses the Dallas Semiconductor "one-wire" interface" ?

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