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Can I Use This For MQTT?

Hi Community,

Pretty green here but will be thankful if anyone could assist!

TL;DR:
I have what looks like the RFM69CW which comes presoldered onto the emonpi. Can I use this to send out LWRF messages from MQTT so I can control some LWRF light switches?

I’ve checked the config and there appears to be a device:

[interfacers]
### This interfacer manages the RFM12Pi/RFM69Pi/emonPi module
[[RFM2Pi]]
Type = EmonHubJeeInterfacer
[[[init_settings]]]
com_port = /dev/ttyAMA0

To me, this just looks like it’s to be used for communicating with other Emon devices…

But I’m a complete nub so won’t pretend to know what I’m looking at. I’m not a total wimp either. I managed to get through the OpenHAB3 documentation, which isn’t really geared up for a complete novice yet, but maybe that’s just me!

So right now I have emonSD-24Jul20 (Stable) running and OpenHAB3 configured showing the power feed on a webpage using MQTT.

Having both lost our jobs, my partner and I are about to leave on a work visa into EU 4 months on conservation work and I’d like to get the lights to come on and off whilst we’re away to make the home look occupied. We can’t afford any slip ups. We’re burning through our savings fast.

I have a couple of LWRF switches to install from ebay…

Welcome, Dave, to the OEM forum.

The short answer is “possibly”.

I found this “The LWRF system operates on 433 MHz and uses simple On/Off Keying (OOK) modulation…”

The RFM69CW is certainly capable of that, but using it assumes that you’re not going to be receiving data from other OEM sensing nodes, like the emonTx or emonTH.

The interfacer in emonHub isn’t intended for that, and in any case the RFM69CW in the emonPi is set up to use JeeLib’s RFM12 emulation mode and FSK. You’d need to completely rewrite the sketch (or the radio part of it), and most likely use somebody else’s library to handle OOK with Lightwave’s protocol and frequency, and write an interfacer (or do it as an app or a service in the Pi) to send the requisite data to it serially.

And of course, the Atmel 328P in the front end has to do that in between doing the energy measurements.

I think your first investigations are an Arduino library for Lightwave, and the Hope RFM69CW data sheet.

Hey Rob,

Thanks for that insight. It’s useful to have someone who knows enough talk about the viability of something before one, such as myself, wasting several hours / days trying.

I can certainly say I’m not going to be doing any re-writing of anything except config files where I find someone else has managed.

I dabbled with a friends emonpi years ago with openhab 1. I think I may need to explore a different radio at this stage. Thanks for your help.

My focus now is to see if I can find an OOK transmitter as described here: Lightwave RF - Guide | OpenEnergyMonitor and set that up using cron jobs…

From how you wrote, I guessed that you were looking for an off-the-shelf solution that could be implemented very quickly and easily.

Take a look at the RS Components website alongside all the usual suspects, for a separate radio module.