water-sensor/water_sensor.ino

#include <ArduinoMqttClient.h>
#include <ESP8266WiFi.h>

#include "secrets.h"

#define ADC_PIN             A0
#define RELAY_PIN           13
#define RELAY_OFF           LOW
#define RELAY_ON            HIGH

#define NUM_SAMPLES         20
#define SAMPLE_TIME         100
#define WATER_THRESHOLD     750

#define MESSAGE_INTERVAL    1000 * 60 * 60  // one hour

WiFiClient wifiClient;
MqttClient mqttClient(wifiClient);

const char broker[] = BROKER;
int        port     = 1883;
const char topic[]  = "iot/water";

String macAddress = String(ESP.getChipId(), HEX);
String shortName = macAddress.substring(0, 4);
String deviceName = "ws_" + shortName;


void relayOn() {
	Serial.println("Setting relay ON");
	digitalWrite(RELAY_PIN, RELAY_ON);
}

void relayOff() {
	Serial.println("Setting relay OFF");
	digitalWrite(RELAY_PIN, RELAY_OFF);
}

bool sampleWater() {
	bool waterDetected = true;

	Serial.print("Samples: ");

	for (int i = 0; i < NUM_SAMPLES; i++) {
		int sample = analogRead(ADC_PIN);
		Serial.print(sample);
		Serial.print(",\t");

		if (sample < WATER_THRESHOLD) {
			waterDetected = false;
		}

		delay(SAMPLE_TIME);
	}

	Serial.println(waterDetected ? "POS" : "NEG");

	return waterDetected;
}

void sendWaterLeakTrue() {
	mqttClient.beginMessage(topic);
	mqttClient.print("{\"id\": \"");
	mqttClient.print(deviceName);
	mqttClient.print("\", \"water_leak\": true}");
	mqttClient.endMessage();
}

void sendWaterLeakFalse() {
	mqttClient.beginMessage(topic);
	mqttClient.print("{\"id\": \"");
	mqttClient.print(deviceName);
	mqttClient.print("\", \"water_leak\": false}");
	mqttClient.endMessage();
}

void setup() {
	pinMode(RELAY_PIN, OUTPUT);

	Serial.begin(115200);
	delay(1000);

	Serial.println();
	Serial.println();
	Serial.println();
	Serial.println("===== BOOT UP =====");

	WiFi.mode(WIFI_STA);
	WiFi.begin(SECRET_SSID, SECRET_PASS);
	Serial.print("[WIFI] Attempting to connect to wifi");
	while (WiFi.status() != WL_CONNECTED) {
		delay(500);
		Serial.print(".");
	}

	Serial.println("");
	Serial.println("[WIFI] Connected to the network");
	Serial.println();

	mqttClient.setId(deviceName);

	Serial.print("[MQTT] Attempting to connect to the MQTT broker: ");
	Serial.println(broker);

	while (!mqttClient.connect(broker, port)) {
		Serial.print("MQTT connection failed! Error code = ");
		Serial.println(mqttClient.connectError());
		delay(5000);
	}

	Serial.println("[MQTT] Connected to the MQTT broker.");

	Serial.println("Turning relay on.");
	relayOn();
}

void loop() {
	static unsigned long last_pos_message = 0;
	static unsigned long last_neg_message = 0;

	bool leakDetected = sampleWater();

	if (leakDetected) {
		relayOff();
		Serial.println("Leak detected");
	}

	mqttClient.poll();

	if (WiFi.status() != WL_CONNECTED) {
		Serial.println("[WIFI] Lost connection. Reconnecting...");
		WiFi.begin(SECRET_SSID, SECRET_PASS);
		return;
	} else if (!mqttClient.connected()) {
		Serial.print("[MQTT] Not connected! Error code = ");
		Serial.println(mqttClient.connectError());
		Serial.println("[MQTT] Reconnecting...");
		mqttClient.connect(broker, port);
		return;
	}

	// TODO: replace this spaghetti with a state machine
	if (leakDetected) {
		if (!last_pos_message || millis() - last_pos_message > MESSAGE_INTERVAL) {
			last_pos_message = millis();
			last_neg_message = 0;
			sendWaterLeakTrue();
		}
	} else {
		if (!last_neg_message || millis() - last_neg_message > MESSAGE_INTERVAL) {
			last_pos_message = 0;
			last_neg_message = millis();
			sendWaterLeakFalse();
		}
	}
}