Text Update Proto

The problem

My specific setup is a Home Assistant integration with ESPHome.

The Nextion firmware has more than 15 text elements that rely on home assistant for their content.

The "original" way of updating the text elements is to use the text_sensor component in ESPHome and update the text elements in the Nextion firmware using the on_value trigger.

But this approach requires a text_sensor per component hence the code becomes a mess really fast...

The solution involves 2 parts:

• Home Assistant side: a text sensor that holds all the text elements in a single string
• ESPHome side: a script that parses the string and updates the text elements in the Nextion display

It's important to note that this approach can be used standalone and there is nothing in this project that relies on this approach/protocol.

I just found it useful for my specific use case. So documenting it here sounds like a good idea.

The protocol

To fix my issue I had to invent a text format that could be easily parsed by the ESPHome script(see below) and HomeAssistant printable.

One caveat I found is that text sensor in Home Assistant does not support states longer than 255 characters. So I used an attribute instead.

The text format is as follows:

$page.$componentName,$value|
$page.$componentName,$value|
|

• $page: is the page name in the Nextion display. If the page is the same for all the components you can omit it.
• $componentName: is the component name in the Nextion display
• $value: is the value to be set in the text component

Between each component there is a |\n separator. The end is marked by a | character.

EspHome side

script:
  - id: restore_nspanel_texts
    then:
      - lambda: |-
          std::string main = id(nspanel_texts).state;   
          std::string md = "| ";   

          size_t pos = 0;   
          int index = 0;   
          while ((pos = main.find(md)) != std::string::npos) {   
            std::string s = main.substr(0, pos);   
            main.erase(0, pos + md.length());  
            std::string delimiter = ",";   
            std::string key = s.substr(0, s.find(delimiter));   
            std::string value = s.substr(key.length() + 1, s.rfind(delimiter) - key.length()  - 1); 
            id(disp1).set_component_text_printf(key.c_str(), "%s", value.c_str());
          }

text_sensor:
  - platform: homeassistant
    id: nspanel_texts
    entity_id: sensor.nspanel_texts
    attribute: value
    on_value:
      then:
        - script.execute: restore_nspanel_texts

Home Assistant side

Home assistant side obviously depends on your personal setup both in HA and Nextion.

Anyways here is a simple example of how to create such sensor.

template:
  - sensor:
    - name: "NSPanel Texts"
      state: >-
        {{ now().strftime('%d-%m-%Y %H:%M:%S') }}
      attributes:
        value: >-
          weather_now.temp_out,{{states('sensor.nspanel_outside_temp')}}|
          weather_now.humidity_out,{{states('sensor.nspanel_outside_humidity')}}|
          weather_now.wind_speed,{{states('sensor.nspanel_outside_windspeed')}}|
          weather_now.sunset,{{states('sensor.nspanel_next_sunset')}}|
          weather_now.sunrise,{{states('sensor.nspanel_next_sunrise')}}|
          |

This is a simple example of how to update the weather information in the Nextion display updating the weather_now page components.

Caveats

As already said a Home Assistant attribute must be used because the state is limited to 255 characters. Also, keep in mind that nextion components should be marked as global.