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https://github.com/idatum/labrfcat

Using rfcat for home automation to control a MInka Aire fan.
https://github.com/idatum/labrfcat

fan home-assistant home-automation minka python rfcat sdr

Last synced: 14 days ago
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Using rfcat for home automation to control a MInka Aire fan.

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## Controlling a Minka Aire fan using rfcat

### Python code to control a Minka ceiling fan using a [Yard Stick One](https://greatscottgadgets.com/yardstickone/) and [rflib](https://github.com/atlas0fd00m/rfcat) module to simulate the Minka remote control (model TR110A, [FCC ID KUJCE10007](https://fccid.io/KUJCE10007)).

![Minka Aire remote](assets/images/minka_remote.png)



I used a series of software tools and hardware, both RTL-SDR and the Yard Stick One, to reverse engineer the remote control commands. This allows me to automate controlling the fan (e.g. using [Home Assistant](https://www.home-assistant.io/) automation).



### Details

Modulation is ASK/OOK. Each 3-bits (octal) transmitted is a symbol for a single bit value: 0 == 010,  1 == 110.

There are 13 symbols per packet, requiring 39 bits to transmit.

Each symbol pulse is ~2.49ms.

![Amplitude time series of packet](assets/images/minka_off.png)



Every packet starts with a single 010 octal (preamble).



The remote's battery compartment has 2 banks of 4 switches, labeled SW8 and SW9.



![Remote switch banks](assets/images/minka_switches.png)



The switch ON/OFF settings are included in the packet.

```

PREAMBLE = '010'

SW8 = '010010010010'

SW9 = '010010110110'

```

On my remote, and the default in code, SW8 is set as OFF OFF OFF OFF, and SW9 is OFF OFF ON ON. Also, I used this as the basis for deciding what octal was either 0 (OFF) or 1 (ON).



Each button produces a unique set of 4 octals, representing a fan command, included in the packet.

```

OFF = '110010110010'

SLOW = '010010110010'

MED = '010110010010'

FAST = '110010010010'

```

There are also octal commands for the fan's LED light. Each single command, for each button on remote, toggles the light. I'm not sure what the different buttons are meant to do. I named the variable LIGHT1 for the top (smaller) button, and LIGHT2 for bottom.

```

LIGHT1 = '010110010110'

LIGHT2 = '110010010110'

```

If you hold down one of the light buttons on the physical remote, you cycle through dimming and brightening the LED light. I didn't implement this, and I really didn't think I'd use it since the LED light on my fan doesn't really dim that well anyway.



Only one command can be sent in a packet.



A complete packet consists of the single preamble octal, 4 octals for the SW8 switch, 4 octals for SW9, and 4 octals for the command. This is a total of 39 bits. The RFxmit method expects a string of bytes, so we have to convert the string representation of the 39 octal bits to a string of bytes with hex escape codes where needed.

```

bits = PREAMBLE + SW8 + SW9 + CMD + '0'

b''.join([struct.pack('B', int(bits[i:i+8], 2)) for i in range(0, len(bits), 8)])

```

This does the trick using the struct module, taking 8 bit chunks from the transmit bits, plus the remaining single zero'd bit to round out 5 bytes (40 bits) total.



I use a spacer of 5 bytes as a timing mechanism between broadcasting each packet, so we add that to the packet that will be broadcast multiple times (8 seems to work) in a burst to make sure the fan receives the transmission.



### Obligatory Home Assistant integration

I integrated this with Home Assistant using the MQTT service. I have a daemon running on the device that has the USB Yard Stuck One plugged in. The daemon is an MQTT client that receives Minka commands via topics and serializes launching a process to execute, for example, ``` python minka.py --cmd=off```.



I can now automatically turn the ceiling fan on based on the temperature of the family room, mostly related to the state of the gas fireplace. Breathtaking, I know 😋



The plan is to integrate more ISM (sub 1Ghz) remote control devices with Home Assistant using my single Yard Stick One.



Pretty fun holiday project!



### References

Many resources to be found. I recommend starting with [Great Scott Gadgets education videos](https://greatscottgadgets.com/sdr/), a great learning resource. You don't need a HackRF (or Yard Stick One) to benefit a lot from this video series.



[rfcat](https://github.com/atlas0fd00m/rfcat#installing-on-hardware)



[gnuradio](https://www.gnuradio.org/): A shockingly bloated set of dependencies, but it really did the job in the end.



[rtl_433](https://github.com/merbanan/rtl_433): This also has analysis tools, besides having a large list of existing devices it can decode.



[Nooelec RTL-SDR](https://www.nooelec.com/store/sdr/nesdr-smart-sdr.html)