Custom settings

Homie for ESP8266 lets you implement custom settings that can be set from the JSON configuration file and the Configuration API. Below is an example of how to use this feature:

HomieSetting<long> percentageSetting("percentage", "A simple percentage");  // id, description

void setup() {
  percentageSetting.setDefaultValue(50).setValidator([] (long candidate) {
    return (candidate >= 0) && (candidate <= 100);


An HomieSetting instance can be of the following types:

Type Value
bool true or false
long An integer from -2,147,483,648 to 2,147,483,647
double A floating number that can fit into a real64_t
const char* Any string

By default, a setting is mandatory (you have to set it in the configuration file). If you give it a default value with setDefaultValue(), the setting becomes optional. You can validate a setting by giving a validator function to setValidator(). To get the setting from your code, use get(). To get whether the value returned is the optional one or the one provided, use wasProvided().

For this example, if you want to provide the percentage setting, you will have to put in your configuration file:

  "settings": {
    "percentage": 75

See the following example for a concrete use case:

GitHub logo CustomSettings.ino