ESP32 Soil pH Monitor

// ESP32 Soil pH Monitor - Advanced (PID dosing + EC + MQTT)
#include <WiFi.h>
#include <PubSubClient.h>
#include <ArduinoJson.h>
#include <OneWire.h>
#include <DallasTemperature.h>

OneWire ow(4); DallasTemperature ds(&ow);
WiFiClient wifiClient; PubSubClient mqtt(wifiClient);

const char* SSID="YourSSID", *PASS="YourPass";
const char* MQTT_HOST="192.168.1.100";
const int PH_PIN=34, EC_PIN=35, PUMP_LIME=25, PUMP_ACID=26;
const float CAL_PH7_RAW=2048.0, CAL_PH4_RAW=1024.0;
const float SLOPE=(7.0f-4.0f)/(CAL_PH7_RAW-CAL_PH4_RAW);
const float INTERCEPT=7.0f-SLOPE*CAL_PH7_RAW;
const float TARGET_PH=6.5f;

// PID coefficients (tune to your soil volume and pump rate)
const float KP=2.0f, KI=0.1f, KD=0.5f;
float integral=0.0f, prevError=0.0f;

float readPH(){
  long s=0; for(int i=0;i<20;i++){s+=analogRead(PH_PIN);delay(10);}
  float raw=s/20.0f; return SLOPE*raw+INTERCEPT;
}
float readEC(){
  // Simplified: voltage divides into EC range; calibrate with known solution
  long s=0; for(int i=0;i<10;i++){s+=analogRead(EC_PIN);delay(5);}
  return (s/10.0f)/4095.0f*2000.0f; // 0-2000 uS/cm approximate
}

void doPID(float ph){
  float err=TARGET_PH-ph;
  integral+=err;
  float deriv=err-prevError;
  float output=KP*err+KI*integral+KD*deriv;
  prevError=err;
  int pumpMs=(int)constrain(abs(output)*100,0,5000);
  if(output>0.2f){ // pH too low, add lime
    digitalWrite(PUMP_LIME,LOW); delay(pumpMs); digitalWrite(PUMP_LIME,HIGH);
    Serial.printf("Lime dose: %d msn",pumpMs);
  } else if(output<-0.2f){ // pH too high, add acid
    digitalWrite(PUMP_ACID,LOW); delay(pumpMs); digitalWrite(PUMP_ACID,HIGH);
    Serial.printf("Acid dose: %d msn",pumpMs);
  }
}

void publishAll(float ph, float ec, float temp){
  StaticJsonDocument<128> doc;
  doc["ph"]=ph; doc["ec"]=ec; doc["temp"]=temp;
  char buf[128]; serializeJson(doc,buf);
  mqtt.publish("soil/sensors",buf);
}

void setup(){
  Serial.begin(115200);
  ds.begin();
  analogReadResolution(12);
  pinMode(PUMP_LIME,OUTPUT); digitalWrite(PUMP_LIME,HIGH);
  pinMode(PUMP_ACID,OUTPUT); digitalWrite(PUMP_ACID,HIGH);
  WiFi.begin(SSID,PASS);
  while(WiFi.status()!=WL_CONNECTED) delay(500);
  mqtt.setServer(MQTT_HOST,1883);
}

void loop(){
  if(!mqtt.connected()) mqtt.connect("SoilMonitor");
  mqtt.loop();
  ds.requestTemperatures();
  float temp=ds.getTempCByIndex(0);
  float rawPH=readPH();
  float ph=(temp!=-127.0f)?rawPH+0.003f*(temp-25.0f):rawPH;
  float ec=readEC();
  publishAll(ph,ec,temp);
  doPID(ph);
  delay(300000); // Dose cycle every 5 minutes
}