Building an RJ45 to RJ12 adapter for the AAG TAI603B weather station

Do you own an AAG TAI603B 1-Wire bus master and want to add other RJ12 sensors from AAG such as the TAI series? This article shows you how.

I recently ordered a 1-Wire weather station kit from AAG (the WS603 kit available here) along with a couple of additional sensors (TAI8750 barometric pressure sensor, TAI8520 temperature sensor, and TAI8540 humidity sensor) for integration with my new home automation system.  The kit includes a 1-Wire USB bus master, conveniently named the TAI603B.  The nice thing about this bus master vs others is that the inputs are opto-isolated, a very nice feature for a weather station indeed (a lightning strike tends to lead to a Very Bad Day for electronics).

I plugged the adapter in to my home automation prototype box and was pleased to see that it was recognized immediately; a quick configuration change to my owfs setup and the adapter was immediately recognized. The weather station was indeed seen by owfs, but as it uses some interesting trickery involving the Maxim DS2780 1-Wire chip to support all of its features it was not yet returning any interesting information. Plugged in the TAI603B temperature sensor via a straight-through cable and… nothing.

The TAI603B bus master unit has two RJ45 connectors for 1-Wire bus connection. Upon further reading, I discovered that the AAG RJ45 pinout is not compatible with the AAG RJ12 pinout; a shame, since the plug does indeed fit. A bit of digging turned up the correct pin assignments; built a quick cable and it does indeed work. Documenting it here for the sake of posterity.

RJ45 Pin Description Cat5 Wire Color RJ12 Pin
1 1-Wire Data white/orange 3
2 1-Wire Gnd orange 4
3 +5v white/green 1
4 +12v blue
5 +12v white/blue
6 +5v green
7 Gnd white/brown
8 Gnd brown 2


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