Home Assistant multisensor on an ESP32-C3

// Home Assistant multisensor: temperature, humidity, light and motion.
//
// The four readings people put in nearly every room, on one ESP32-C3:
//   DHT22 on GPIO 3     temperature and humidity, read every 10 seconds
//   BH1750 on I2C       light in lux (SDA GPIO 4, SCL GPIO 5)
//   PIR on GPIO 18      motion, reported the moment it changes
//   LED on GPIO 19      lights while the PIR sees motion
//
// On a real device you would most likely flash ESPHome and write YAML instead
// of this sketch. Mokxi runs Arduino code, not ESPHome, so this sketch does by
// hand what ESPHome's dht, bh1750 and gpio binary_sensor components do, and
// the help page shows the YAML side by side.
//
// What reaches Home Assistant. The network here is SIMULATED and has no MQTT
// broker, so the sketch prints each message it would publish, one line per
// topic, and serves the same values as JSON at /state for the Web tab. Home
// Assistant's RESTful sensor can poll a URL like that on a real network.

#include <BH1750.h>
#include <DHT.h>
#include <WebServer.h>
#include <WiFi.h>
#include <Wire.h>

const int DHT_PIN = 3;
const int PIR_PIN = 18;
const int LED_PIN = 19;

const unsigned long CLIMATE_EVERY_MS = 10000;  // a DHT22 wants 2 s at least
const unsigned long LIGHT_EVERY_MS = 5000;
const float LUX_CHANGE = 10.0;  // only report light that has really changed

DHT dht(DHT_PIN, DHT22);
BH1750 lightMeter;
WebServer server(80);

float temperature = 0;
float humidity = 0;
float lux = 0;
float luxSent = -1000;
bool motion = false;
unsigned long lastClimate = 0;
unsigned long lastLight = 0;

// One line per message a real device would publish to its MQTT broker.
void publish(const char *topic, const String &payload) {
  Serial.print("publish home/multisensor/");
  Serial.print(topic);
  Serial.print(' ');
  Serial.println(payload);
}

void readClimate() {
  float t = dht.readTemperature();
  float h = dht.readHumidity();
  if (isnan(t) || isnan(h)) {
    Serial.println("DHT22: no answer, check the data wire and its pull-up");
    return;
  }
  temperature = t;
  humidity = h;
  publish("temperature", String(temperature, 1));
  publish("humidity", String(humidity, 1));
}

void readLight() {
  lux = lightMeter.readLightLevel();
  if (fabs(lux - luxSent) >= LUX_CHANGE) {
    luxSent = lux;
    publish("illuminance", String(lux, 0));
  }
}

void sendState() {
  String json = "{\"temperature\":";
  json += String(temperature, 1);
  json += ",\"humidity\":";
  json += String(humidity, 1);
  json += ",\"illuminance\":";
  json += String(lux, 0);
  json += ",\"motion\":";
  json += motion ? "true" : "false";
  json += "}";
  server.send(200, "application/json", json);
}

void sendPage() {
  String page = "<!doctype html><html><head><meta charset=\"utf-8\">";
  page += "<title>Multisensor</title></head><body><h1>Living room</h1><p>";
  page += String(temperature, 1);
  page += " &deg;C &middot; ";
  page += String(humidity, 0);
  page += "% &middot; ";
  page += String(lux, 0);
  page += " lx &middot; motion ";
  page += motion ? "detected" : "clear";
  page += "</p><p><a href=\"/state\">/state as JSON</a></p></body></html>";
  server.send(200, "text/html", page);
}

void setup() {
  Serial.begin(115200);
  pinMode(PIR_PIN, INPUT);
  pinMode(LED_PIN, OUTPUT);
  dht.begin();
  Wire.begin(4, 5);  // SDA, SCL
  lightMeter.begin();

  Serial.println("Multisensor: simulated WiFi, no MQTT broker in Mokxi.");
  WiFi.begin("Mokxi-Lab", "breadboard");
  while (WiFi.status() != WL_CONNECTED) {
    delay(250);
  }
  Serial.print("online at http://");
  Serial.print(WiFi.localIP());
  Serial.println("/state");
  server.on("/", sendPage);
  server.on("/state", sendState);
  server.begin();

  delay(2000);  // the DHT22 needs a moment after power-up
  readClimate();
  readLight();
  publish("motion", "OFF");
  lastClimate = lastLight = millis();
}

void loop() {
  server.handleClient();

  // Motion is the one reading worth sending the instant it changes.
  bool seen = digitalRead(PIR_PIN) == HIGH;
  if (seen != motion) {
    motion = seen;
    digitalWrite(LED_PIN, motion ? HIGH : LOW);
    publish("motion", motion ? "ON" : "OFF");
  }

  unsigned long now = millis();
  if (now - lastClimate >= CLIMATE_EVERY_MS) {
    lastClimate = now;
    readClimate();
  }
  if (now - lastLight >= LIGHT_EVERY_MS) {
    lastLight = now;
    readLight();
  }
  delay(5);
}