Support for Holman smart taps and irrigation controllers?

[victorhooi]

It seems that rtl_433 already has support for the Holman weather sensors:

#947

I was wondering if anybody had looked into adding support for the Holman tap valves and irrigation controllers?

• WX1 tap controller
• WX2 Dual-outlet tap controller
• WX4 Four-outlet tap controller
• WX1 Solar Tap Controller
• WX8 Irrigation Controller

From the packaging, they also seem to operate on the 917Mhz band.

They're fairly common sold here in Australia (e.g. at Bunnings)

The Holman system uses a proprietary wifi-hub which plugs into a power point:

The hub also doubles as a smart plug.

The hub communicates with the actual water valve itself over 917Mhz:

From this discussion and this one, it seems they're Tuya devices under the hood.

However, I would be keen to see if the valves could be used directly via rtl_433, rather than using the proprietary Holman hubs.

What do people think?

Assuming I can get my hands on a device - what would be involved in adding support?

[zuckschwerdt]

If you get your hands on any interesting device recommended first steps are:

• get a sample to inspect the timing and modulation. Preferably without SDR antenna from ~50 cm distance. We want an isolated signal that is not clipping (too loud). https://triq.org/rtl_433/ANALYZE.html
• maybe get new samples if the sample rate was too low (for very fast transmissions) or the center frequency was not ideal (you want to be 20 kHz to 50 kHz off from the actual carrier).
• Use a flex decoder (built from the modulation and timing info) to grab series of codes to analyze.

[ProfBoc75]

@victorhooi , it's look like Bresser SmartHome Garden, you may be interested by #3005 and #2988 , this is a bidirectional protocol (tx/rx), with Wifi base station, pairing mechanism and so on.

Unfortunately I didn't work on it since a while, and I don't have such devices ...

Try my PR from #3005 (branch feat-bresser_soil_moisture) and see how it behaves, may be you will identify some useful information and continue to contribute here.
As I can see from Holman family there are few other sensors compare to Bresser, so good to get more sensors, hope compatible.

[victorhooi]

@zuckschwerdt Got it - thanks for the advice!

I'll read through https://triq.org/rtl_433/ANALYZE.html, but I may also need to brush up my RF fundamentals again, haha.

I have an old RTL-SDR V4, with the official antenna kit.

Good tip about removing the antenna. I hadn't thought of that - I guess old habit, I was taught to never run RF TX equipment without the antenna, but then it just clicked, the RTL-SDR is RX only 😁. So I'm all safe, right?

Unfortunately I don't have access to a Faraday bag or RF blockbox on me at the moment =(, and not sure how noisy the RF environment here is. However, maybe the removing antenna trick is enough.

Also - I've just realised something 🤦‍♂️ - rtl_433 is only for receiving, right?

So if we needed bi-directional RF to control the water tap timer - that won't work in rtl_433 at all?

Or is there some extension to rtl_433 that lets you transmit and control devices as well?

@ProfBoc75 Oh nice - I'll have a look at those Bresser devices. They seem to be mostly EU-specific though, right?

I saw they use the 868Mhz band as well, right?

How come you stopped working on the Bresser integration - is it because you don't have those devices anymore?

Also - how did you tackle the TX/bi-directional thing with the Bresser tap timers?

[ProfBoc75]

Also - I've just realised something 🤦‍♂️ - rtl_433 is only for receiving, right?

Yes, correct.

So if we needed bi-directional RF to control the water tap timer - that won't work in rtl_433 at all?

Yes, rtl_433 is able to receive only. Solution based on famous CC1101 and ESP32 could work, but it needs some knowledge and work to achieve what you want.
Sometime, it's possible to use the equipment itself using specific API, here may be Tuya API ? Sometime you may have an alternative firmware, but it's at your own risk.

Or is there some extension to rtl_433 that lets you transmit and control devices as well?

rtl_433 can be used to listen and to send information to an external solution (MQTT/HA ... ) where you can trigger actions using another hardware.

@ProfBoc75 Oh nice - I'll have a look at those Bresser devices. They seem to be mostly EU-specific though, right?

I saw they use the 868Mhz band as well, right?

ISM frequencies are not the same between US mostly 915 MHz / EU 868 MHz... look at the README home page of rtl_433:

• rtl_433 (despite the name) is a generic data receiver, mainly for the 433.92 MHz, 868 MHz (SRD), 315 MHz, 345 MHz, and 915 MHz ISM bands.

Most of the time, even if the frequency is not the same, the protocol is the same and could work.

How come you stopped working on the Bresser integration - is it because you don't have those devices anymore?

Correct, my contribution here, was based on other contributors, see my explanation just below.

Also - how did you tackle the TX/bi-directional thing with the Bresser tap timers?

First, you must use the equipment normally (i.e., configured and functional) and rtl_433 will listen and capture each frame in parallel, which you must identify correctly. It is important to proceed slowly, one action at a time, in order to identify the data correctly. Thanks to our contributors, we have captured many frames / codes.
For each use case, you have a specific behavior and specific frames/codes. Here, for each action, the target equipment acknowledges the author of the action, so it is a bidirectional protocol.
Gradually, with experience, I was able to identify this bidirectional protocol and its behavior. I was able to identify the base, the humidity sensor, and the timer, but I was limited by my own availability (still the case unfortunately) and the availability of contributors.