ESP32 Greenhouse Automation Controller

// ESP32 Greenhouse - Advanced (PID CO2 + MQTT telemetry)
#include <WiFi.h>
#include <PubSubClient.h>
#include <ArduinoJson.h>
#include <DHT.h>
#include <time.h>

DHT dht(4,DHT22);
WiFiClient wc; PubSubClient mqtt(wc);
const char* SSID="YourSSID", *PASS="YourPass";
const char* MQTT_HOST="192.168.1.100";

const int CO2_VALVE_PWM=25, R_FAN=26, R_LIGHT=27;
const int LIGHT_ON=6, LIGHT_OFF=22;
const float CO2_TARGET=1000.0f; // ppm setpoint

// Simple PID for CO2 valve duty cycle
float pidKp=0.5f, pidKi=0.05f, pidKd=0.1f;
float pidIntegral=0, pidPrevErr=0;

float computePID(float measured, float dt){
  float err=CO2_TARGET-measured;
  if(measured>CO2_TARGET) err=0; // only inject, never extract
  pidIntegral+=err*dt;
  pidIntegral=constrain(pidIntegral,-200,200);
  float derivative=(err-pidPrevErr)/dt;
  pidPrevErr=err;
  float out=pidKp*err+pidKi*pidIntegral+pidKd*derivative;
  return constrain(out,0,255);
}

int readCO2(){
  uint8_t cmd[9]={0xFF,0x01,0x86,0,0,0,0,0,0x79};
  Serial2.write(cmd,9); delay(100);
  if(Serial2.available()<9) return -1;
  uint8_t r[9]; Serial2.readBytes(r,9);
  return (r[0]==0xFF&&r[1]==0x86)?(r[2]<<8)|r[3]:-1;
}

void publishTelemetry(float t,float h,int co2,int duty){
  StaticJsonDocument<192> doc;
  doc["temp"]=t; doc["hum"]=h; doc["co2"]=co2; doc["co2_duty"]=duty;
  char buf[192]; serializeJson(doc,buf);
  mqtt.publish("greenhouse/telemetry",buf);
}

void setup(){
  Serial.begin(115200);
  Serial2.begin(9600,SERIAL_8N1,16,17);
  dht.begin();
  ledcSetup(0,1000,8); ledcAttachPin(CO2_VALVE_PWM,0);
  pinMode(R_FAN,OUTPUT); digitalWrite(R_FAN,HIGH);
  pinMode(R_LIGHT,OUTPUT); digitalWrite(R_LIGHT,HIGH);
  WiFi.begin(SSID,PASS);
  while(WiFi.status()!=WL_CONNECTED) delay(500);
  configTime(0,0,"pool.ntp.org");
  mqtt.setServer(MQTT_HOST,1883);
}

unsigned long lastT=0;
void loop(){
  if(!mqtt.connected()) mqtt.connect("Greenhouse");
  mqtt.loop();
  unsigned long now=millis();
  float dt=(now-lastT)/1000.0f; lastT=now;

  float temp=dht.readTemperature(), hum=dht.readHumidity();
  int co2=readCO2();
  bool fanOn=(temp>28||hum>80);
  digitalWrite(R_FAN,fanOn?LOW:HIGH);

  int co2Duty=0;
  if(co2>0&&!fanOn) co2Duty=(int)computePID((float)co2,dt);
  ledcWrite(0,co2Duty);

  struct tm ti; getLocalTime(&ti);
  bool lightOn=(ti.tm_hour>=LIGHT_ON&&ti.tm_hour<LIGHT_OFF);
  digitalWrite(R_LIGHT,lightOn?LOW:HIGH);

  publishTelemetry(temp,hum,co2,co2Duty);
  Serial.printf("T:%.1f H:%.1f CO2:%d duty:%dn",temp,hum,co2,co2Duty);
  delay(30000);
}