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06_MQTT_Control.md

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MQTT Control

MQTT Namespace

By default the device will subscribe to homeassistant/haswitchplate/<node_name>/# to accept incoming commands. There are two subtopics to send commands to and receive messages from the panel:

  • command will send commands or set attribute of the display, such as button text or screen dim. The specific attribute must be appended as a subtopic, with the value to be set delivered as the payload. For example, the following command will set the text displayed on page 1/button 4 to "Lamp On": mosquitto_pub -h mqtt -t homeassistant/haswitchplate/nodename/command/p[1].b[4].txt -m '"Lamp On"'
  • state topics will be sent by the panel in response to local user interactions or received commands which provide output in return. For example, a user pressing button 4 on page 1 will cause the panel to publish a message: 'homeassistant/haswitchplate/nodename/command/p[1].b[4]' 'ON'

command Syntax

Messages sent to the panel under the command topic will be handled based on the following rules:

  • '[...]/command' 'dim 100' A command with no subtopic will send the command in the payload to the panel directly.
  • '[...]/command/page' '1' The page command subtopic will set the current page on the device to the page number included in the payload.
  • '[...]/command/update' 'http://192.168.0.10:8123/local/HASwitchPlate.tft' The update command subtopic attempts to update the Nextion LCD from the file URL named in the payload.
  • '[...]/command/p[1].b[4].txt' '"Lamp On"' A command with a subtopic will set the attribute named in the subtopic to the value sent in the payload. You can send these messages with retain enabled and the broker will remember these settings for you.
  • '[...]/command/p[1].b[4].txt' '' A command with a subtopic and an empty payload will request the current value of the attribute named in the subtopic from the panel. The value will be returned under the state topic as '[...]/state/p[1].b[4].txt' '"Lamp On"'

Detailed documentation on the Nextion command instruction set can be found here. Note that some values require quotes, while others don't, and different shells (and Home Assistant config files) eat quotes differently. As a general rule, attributes which accept an numeric value cannot have quotes, all other attributes must be enclosed in double quotes.

Objects are referenced by page number (not page name) and object ID (not object name) as shown in the Nextion editor. The Nextion notation for each object is of the form p[1]b[2] meaning page number 1, object number 2. Confusingly, button objects will be named starting at b0 but it might be object 2, or 7, etc. Other objects will be named similarly with different letters. For example, the first text field on the page will be automatically named t0. These names have nothing to do with the object ID, and all objects regardless of type are still referenced as p[<page number>].b[<object id>]

Page and Object IDs

While it is possible to send command messages using the object or page names, all messages coming back from the panel under state will be using page numbers and object IDs. Save yourself the confusion and do everything in the format p[<page number>].b[<object id>] and things will go easier.