What incoming value transformation for MQTT channel for HomeAssistant value

Add-ons Bindings
1

I’m trying to read some values from a Fox hybrid inverter. I tried first to use the MODBUS binding but couldn’t get it it read any data so cheated and installed a HomeAssistant VM and the Fox ESS Modbus integration is able to read data from the inverter. I then added the MQTT addon and have HA publishing data to my MQTT broker.

I’ve created a thing to represent the inverter MQTT data and have added a channel but can’t seem to configure the MQTT state topic and incoming value transformation correctly to read any data. For example, the battery discharge rate looks like this in MQTT explorer:

image
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homeassistant/sensor/garage_battery_discharge/state

I want to get the state value, in the above screenshot it’s 0.654. I’ve set the incoming state topic to:

homeassistant/sensor/garage_battery_discharge

And the incoming transformation to:

JSONPATH:$./state

I’ve tried setting the state topic to just homeassistant/sensor and changing the incoming transformation to JSONPATH:$./garage_battery_discharge/state. I’ve added dots, I’ve removed dots, I’ve added slashes, I’ve removed them. I feel like I’ve tried all the combos but the linked item always stays NULL.

The linked item is type number with dimension power and unit kW, the semantic point is Measurement and Property is Power. The channel profile is Follow.

Any suggestions on how to get this to work? I’ve got other MQTT things reading data from some zigbee sensors that work perfectly well.

2

Not sure you need a JSONPATH transformation there. Try setting your state topic to:

homeassistant/sensor/garage_battery_discharge/state

Assuming you are using a Generic MQTT thing, create the item as a number type with UOM kW.

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3

A-ha! That fixed it! I’d tried every combination of dots and slashes in the incoming transformation except for having no transformation at all.

Thank you very much for your help :slight_smile:

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