# Create a circuit to act as the secondary controller which will interface with a home automation system

**URL:** <https://forum.inductiveautomation.com/t/create-a-circuit-to-act-as-the-secondary-controller-which-will-interface-with-a-home-automation-system/17222>\
**Category:** General Discussion\
**Created:** [March 5, 2018, 1:53pm UTC](https://forum.inductiveautomation.com/t/create-a-circuit-to-act-as-the-secondary-controller-which-will-interface-with-a-home-automation-system/17222 "2018-03-05T13:53:29Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![18018756574](https://avatars.discourse-cdn.com/v4/letter/1/e8c25b/32.png) [@18018756574](https://forum.inductiveautomation.com/u/18018756574)\
**Post date:** [March 5, 2018, 1:53pm UTC](https://forum.inductiveautomation.com/t/create-a-circuit-to-act-as-the-secondary-controller-which-will-interface-with-a-home-automation-system/17222/1 "2018-03-05T13:53:29Z")

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I just installed a Daikin split system (AC/Heat Pump) and would like to control it remotely. There are similar units available which can be controlled with an[IR remote](http://www.kynix.com/Product/Cate/189.html), but mine does not support this option. The only way to control it is to use their thermostat device which uses an unknown protocol to send commands to the indoor and outdoor units.

Here are the model numbers for the components in the system:  
Indoor Unit - FCQ18PAVJU  
Outdoor Unit - RZQ18PVJU9  
Remote Control - BRC1E72

The remote controller is powered and transmits data over the two wire cable that connects it to the indoor unit.

The system supports a second controller as a slave, so the ultimate goal is to create a circuit to act as the secondary controller which will interface with a home automation system.

I have sampled the signal with an oscilloscope to see what’s going on, but I’m not sure how to proceed with decoding the format.

Partial Zoom (One Wire)

 ![](https://us1.discourse-cdn.com/inductiveautomation/original/2X/f/f9906346a971ac95994670ce76ba706b6a420180.png)

The signal has a DC offset which is mirrored by the voltage on the other wire. The sum of the voltages on the two wires is always exactly zero. On the small scale, it is sinusoidal. There are regular fluctuations in amplitude, but I’m not seeing a bit pattern. Maybe it is frequency encoded.

See the full 2.4 second capture here in .csv format: [Dropbox - daikin\_0.csv - Simplify your life](https://www.dropbox.com/s/ufat8huv6hmi0fk/daikin_0.csv?dl=0)

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**Author:** ![R.Alamsha](https://avatars.discourse-cdn.com/v4/letter/r/e5b9ba/32.png) [@R.Alamsha](https://forum.inductiveautomation.com/u/R.Alamsha)\
**Post date:** [March 5, 2018, 3:09pm UTC](https://forum.inductiveautomation.com/t/create-a-circuit-to-act-as-the-secondary-controller-which-will-interface-with-a-home-automation-system/17222/2 "2018-03-05T15:09:58Z")

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May be you need some protocol gateway. Check this answer.

> [@Connecting Ignition to an iNOEX production line?](http://forum.inductiveautomation.com/t/connecting-ignition-to-an-inoex-production-line/17083/3):
>
> I have come across these kind of systems. One such system was running on a “top secret” soft PLC written in c language. My guess is mostly it will be a Modbus PLC. Find the communication cable, connect it to your laptop, and use some data capturing tools or protocol sniffer which is freely available on internet. Copy paste the data packets and do some google research. You will get some clue. I did this technique to develop a communication driver for a top secret control panel and found it was Mo…