Smart Temperature Locker

// Smart Locker: 3.3V logic with isolated external 5V load rail.
#include <Arduino.h>
#include <WiFi.h>
#include <WebServer.h>
#include <DHT.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <ESP32Servo.h>
#include <Preferences.h>
#include <esp_system.h>
#include "locker_ui.h"
DHT sensor(4,DHT22);
LiquidCrystal_I2C lcd(0x27,16,2);
float distanceCm=NAN;
String previousLine1,previousLine2;
Servo latch;
WebServer server(80);
Preferences prefs;
const char* admin="locker-demo-2026";
String state="empty", otp="", category="normal";
float temperature=NAN, humidity=NAN, target=30;
bool fan=false, closed=false, rawClosed=false, lastRaw=false, openingSeen=false;
uint32_t edge=0, sample=0, issued=0, unlockedAt=0, blockedAt=0;
int failures=0;
bool pending=false, blocked=false;
void save(){prefs.putString("state",state); prefs.putString("category",category);}
void reply(int code,String text){server.send(code,"application/json",text);}
bool auth(){if(server.header("X-Admin-Key")==admin)return true;reply(403,"{\"error\":\"admin_key\"}");return false;}
void mint(){char b[7];snprintf(b,sizeof(b),"%06lu",(unsigned long)(100000+esp_random()%900000));otp=b;issued=millis();failures=0;}
void status(){
 String j="{\"state\":\""+state+"\",\"category\":\""+category+"\",\"temperature\":";
 j+=isnan(temperature)?String("null"):String(temperature,2);
 j+=",\"humidity\":"+(isnan(humidity)?String("null"):String(humidity,1));
 j+=",\"distanceCm\":"+(isnan(distanceCm)?String("null"):String(distanceCm,1));
 // Demo occupancy threshold: calibrate to the actual empty compartment.
 j+=",\"packagePresent\":"+(isnan(distanceCm)?String("null"):String(distanceCm<20?"true":"false"));
 j+=",\"target\":"+String(target)+",\"fan\":"+(fan?"true":"false")+",\"doorClosed\":"+(closed?"true":"false")+",\"sensorFault\":"+(isnan(temperature)?"true":"false")+"}";
 reply(200,j);
}
void setup(){
 Serial.begin(115200);pinMode(14,OUTPUT);digitalWrite(14,LOW);pinMode(23,OUTPUT);pinMode(19,OUTPUT);pinMode(26,OUTPUT);pinMode(25,OUTPUT);digitalWrite(25,LOW);pinMode(18,INPUT);pinMode(27,INPUT_PULLUP);
 closed=lastRaw=digitalRead(27)==LOW;
 latch.setPeriodHertz(50);latch.attach(13,500,2400);latch.write(closed?10:90);
 prefs.begin("locker",false);state=prefs.getString("state","empty");category=prefs.getString("category","normal");target=category=="ventilated"?28:30;
 // Interrupted transactions need admin inspection; never infer delivery from reboot.
 if(state!="empty" && state!="waiting")state="recovery";
 sensor.begin();Wire.begin(21,22);Wire.setClock(100000);lcd.init();lcd.backlight();
 WiFi.mode(WIFI_AP);WiFi.softAP("SmartLocker-Demo","LockerDemo2026");
 const char* headers[]={"X-Admin-Key"};server.collectHeaders(headers,1);
 server.on("/",HTTP_GET,[](){server.send_P(200,"text/html; charset=utf-8",LOCKER_UI);});
 server.on("/status",HTTP_GET,status);
 server.on("/deposit",HTTP_POST,[](){
  if(!auth())return;
  if(state!="empty"||!closed){reply(409,"{\"error\":\"not_empty_or_door_open\"}");return;}
  category=server.arg("category");if(category!="normal"&&category!="ventilated"){reply(400,"{\"error\":\"category\"}");return;}
  target=category=="ventilated"?28:30;state="loading";openingSeen=false;unlockedAt=millis();latch.write(90);save();status();
 });
 server.on("/otp",HTTP_POST,[](){if(!auth())return;if(state!="waiting"){reply(409,"{}");return;}mint();reply(200,"{\"otp\":\""+otp+"\",\"expiresSeconds\":300}");});
 server.on("/unlock",HTTP_POST,[](){
  if(blocked){reply(429,"{\"error\":\"wait_60_seconds\"}");return;}
  if(state!="waiting"||otp.length()!=6||millis()-issued>=300000){otp="";reply(403,"{\"error\":\"expired_or_missing\"}");return;}
  if(server.arg("otp")!=otp){if(++failures>=5){blocked=true;blockedAt=millis();otp="";}reply(403,"{\"error\":\"wrong_otp\"}");return;}
  otp="";state="collecting";openingSeen=false;unlockedAt=millis();latch.write(90);save();status();
 });
 server.on("/reset",HTTP_POST,[](){if(!auth())return;if(!closed){reply(409,"{}");return;}state="empty";otp="";latch.write(10);save();status();});
 server.begin();Serial.println("WiFi SmartLocker-Demo / LockerDemo2026; http://192.168.4.1");
}
void loop(){
 server.handleClient();uint32_t now=millis();
 rawClosed=digitalRead(27)==LOW;if(rawClosed!=lastRaw){lastRaw=rawClosed;edge=now;}if(now-edge>80)closed=rawClosed;
 if(blocked&&now-blockedAt>=60000){blocked=false;failures=0;}
 if(state=="loading"||state=="collecting"){
  if(!closed)openingSeen=true;
  if(closed && openingSeen){latch.write(10);state=state=="loading"?"waiting":"empty";save();}
  else if(closed && now-unlockedAt>30000){latch.write(10);state=state=="loading"?"empty":"waiting";save();}
 }
 if(now-sample>=2500){
  sample=now;temperature=sensor.readTemperature();humidity=sensor.readHumidity();
  digitalWrite(25,HIGH);delayMicroseconds(10);digitalWrite(25,LOW);
  unsigned long duration=pulseIn(18,HIGH,25000);distanceCm=duration?duration/58.0f:NAN;
 }
 bool next=fan;
 if(isnan(temperature))next=true;
 else if(temperature>=target+0.5f)next=true;
 else if(temperature<=target-0.5f)next=false;
 fan=next;digitalWrite(14,fan?HIGH:LOW);
 // LEDs simulate thermal modes only: no Peltier is connected.
 digitalWrite(23,!isnan(temperature)&&fan);
 digitalWrite(19,!isnan(temperature)&&temperature<target-0.5f);
 static uint32_t alarmAt=0;
 if((!closed && now-unlockedAt>30000)||isnan(temperature)){
  if(now-alarmAt>3000){tone(26,4000,100);alarmAt=now;}
 }
 String line1=isnan(temperature)?"TEMP ERROR":String(temperature,1)+"C "+(fan?"FAN ON":"FAN OFF");
 String line2=(closed?String("Closed "):String("Open "))+(isnan(distanceCm)?"--":String(distanceCm,0))+"cm";
 if(line1!=previousLine1){lcd.setCursor(0,0);lcd.print("                ");lcd.setCursor(0,0);lcd.print(line1);previousLine1=line1;}
 if(line2!=previousLine2){lcd.setCursor(0,1);lcd.print("                ");lcd.setCursor(0,1);lcd.print(line2);previousLine2=line2;}
}

// Pin mapping confirmed: TRIG25 ECHO18 servo13 relay14 door27 buzzer26 SDA21 SCL22.