Modbus

Essentially, they're all message frameworks, right? Between EA, UA, MQTT.

And actually, I forgot Modbus, which is always a

good kick, too.

No, I don't want to talk about Modbus.

I've spent too much time talking about Modbus in my career.

Particularly about why it ain't working.

Yeah.

Oh,

So now he's asking the questions that probably should have come before the purchase, which is exactly how every good home automation project starts.

What do the specs actually mean when you're wiring an RGB PWM controller? What are the voltage and wiring limits when you're running lights in a strip? How do you waterproof the controller and the first mains connection for an outdoor spot? And do these things exist in Modbus or some other proprietary system, or is it Zigbee and Matter only? And the practical question underneath all of it, what should a first-timer actually buy for a few smart spotlights on a patio running through Home Assistant?

The modular instinct is right.

The old light was a sealed unit, so when the driver died, the whole thing became e-waste.

Critical.

Most of these controllers are designed for common anode strips where the positive rail is shared and each color channel switches the negative side.

The HomeMaster Modbus unit, for example, explicitly says connect the LED positive to the common terminal and each color cathode to its channel.

If you buy a common cathode strip and wire it to a common anode controller, nothing works, and you might damage the controller.

I think I think it was a really cool exercise in the versatility of the platform we built because we built it on other battery vendors and solar providers.

But as long as we can talk Modbus or Canvas or any of the standard protocols, we can talk and control systems.

And so we were able to go in, install our controller and take control.

There's like four megawatts of solar and four megawatt hours of batteries and two megawatts of inverter output that's spread across 17 batteries.

I'm going to butcher their name, but either way, there is a wide list of technologies out there present for A2L sensors and how they do it.

And some of them are communicating via Modbus from the sensor back to the control board.

And then that is just an open-close relay on the system.

Everybody keeps asking me, they're like, oh, are we going to see the parts per million of refrigerant within the system? And it's like, no, no, no.

And then it's going to say, hey, refrigerant, no refrigerant, refrigerant, no refrigerant.

We're not doing parts per million from what I understand.

And they're like, well, if it's Modbus, then we can just watch the communication and then relay that information.

It's like, don't overcomplicate this.

which are essentially doing roughly the same job in the sense that both of them are boxes which talk to your heat pump via the same communication.

It's a language called Modbus, that's what they all use.

So all it does is it asks a question and gets a reply.

So there's no problem with sticking the two on together.

And...

And that title is a very direct hint at one of the biggest architectural changes in this release, a modernization of Modbus support.

It may not be the flashiest dashboard feature, but for solar inverters, heat pumps, ventilation systems, and energy meters, it is a big deal.

Let's start there, because Modbus can sound intimidating if you're new.

Traditionally, Home Assistant could talk to Modbus devices, but you often had to write YAML yourself.

That meant knowing register addresses, data types, scaling, and the exact way your device exposes values.

which is powerful, but also a barrier.

In 2026.9, Home Assistant lays the groundwork for integrations that already understand a device's Modbus protocol.

The power of Home Assistant at the moment, though, is Home Assistant now is so many protocols, so many devices.

Even in 2026.9, we're about to talk about Modbus.

Home Assistant has serial devices.

It's got Zigbee, Matter.

But yeah, that's cool.

All right.

Modbus.

Modbus, if you're not familiar with it, it's a common language used in industrial and electrical devices to talk to each other.