Generator Remote Monitor

#include <Arduino.h>
#include <WiFi.h>
#include <WebServer.h>
#include <Preferences.h>
#include <esp_system.h>

// DFR0473: HIGH energizes coil; external 10k pull-down holds OFF at reset.
constexpr uint8_t RELAY_PIN=26, ENABLE_PIN=27, RUN_PIN=32, ALARM_PIN=33, MAINS_PIN=25;
constexpr uint32_t LEASE_MS=20000, MAX_RUN_MS=30UL*60UL*1000UL, FEEDBACK_MS=90000;
// ADC1 works while Wi-Fi is active; GPIO34 is input-only by design.
constexpr uint8_t FUEL_PIN=34;
int fuelPercent=-1;
float fuelOhms=0;
String fuelState="Waiting for sender";
uint32_t fuelSampleAt=0, fuelStableAt=0;
int fuelCandidate=-1;
WebServer server(80);
Preferences prefs;
String ssid, wifiPassword, adminPassword, csrf, setupPassword;
bool setupMode=false, requested=false;
uint32_t leaseAt=0, startAt=0, missingAt=0, restartAt=0;
String events[24];
uint8_t logHead=0, logCount=0;
struct Contact {
  uint8_t pin; bool raw=false, closed=false; uint32_t changed=0;
  void begin(){pinMode(pin,INPUT_PULLUP);raw=digitalRead(pin)==LOW;closed=raw;changed=millis();}
  bool update(){bool v=digitalRead(pin)==LOW;if(v!=raw){raw=v;changed=millis();}if(closed!=raw && millis()-changed>=100){closed=raw;return true;}return false;}
};
Contact running{RUN_PIN}, alarmContact{ALARM_PIN}, mainsContact{MAINS_PIN}, key{ENABLE_PIN};
bool connected(){return !setupMode && WiFi.status()==WL_CONNECTED;}
void logEvent(const String &s){events[logHead]=String(millis()/1000)+"s: "+s;logHead=(logHead+1)%24;if(logCount<24)++logCount;Serial.println(s);}
// KUS American curve is NONLINEAR. These five points are from the maker.
// Percentage is approximate indicated level, NOT calibrated tank volume.
int levelFromOhms(float r){
 const float ohms[]={240,142.5f,105,67.5f,33};
 if(r>=240)return 0;if(r<=33)return 100;
 for(int i=0;i<4;i++)if(r<=ohms[i] && r>=ohms[i+1])
  return (int)roundf(i*25.0f+25.0f*(ohms[i]-r)/(ohms[i]-ohms[i+1]));
 return 0;
}
void updateFuel(uint32_t now){
 if(now-fuelSampleAt<500)return;
 fuelSampleAt=now;
 uint32_t sum=0;for(int i=0;i<16;i++)sum+=analogReadMilliVolts(FUEL_PIN);
 float mv=sum/16.0f;
 // Nominal 3.3 V excitation; ADC/supply/lead resistance introduce error.
 float r=mv<3250?330.0f*mv/(3300.0f-mv):100000;
 int candidate=(mv<100)?-2:((mv>2200 || r>280 || r<20)?-3:levelFromOhms(r));
 // Confirm five seconds to suppress float slosh and transient contact changes.
 // Quantize to 5% steps; resolution is also limited by the sender reed spacing.
 if(candidate>=0)candidate=constrain((candidate+2)/5*5,0,100);
 if(candidate!=fuelCandidate){fuelCandidate=candidate;fuelStableAt=now;}
 if(now-fuelStableAt<5000)return;
 String next=candidate==-2?"FAULT: short or wrong sender":candidate==-3?"FAULT: open wire or out of range":candidate<=20?"LOW DIESEL (20% or less)":"Normal";
 fuelPercent=candidate>=0?candidate:-1;fuelOhms=r;
 if(next!=fuelState){fuelState=next;logEvent("Fuel: "+next);}
}
void stopRequest(const String &reason){digitalWrite(RELAY_PIN,LOW);if(requested){requested=false;logEvent(reason);}}
bool safeToStart(){return millis()>2000 && connected() && key.closed && digitalRead(ENABLE_PIN)==LOW && !alarmContact.closed && digitalRead(ALARM_PIN)==HIGH;}
bool auth(){if(server.authenticate("admin",adminPassword.c_str()))return true;server.requestAuthentication();return false;}
bool postAuth(){if(!auth())return false;if(!server.hasArg("token")||server.arg("token")!=csrf){server.send(403,"text/plain","Invalid session. Reload dashboard.");return false;}return true;}
String htmlEscape(String s){s.replace("&","&amp;");s.replace("<","&lt;");s.replace(">","&gt;");s.replace("\"","&quot;");s.replace("'","&#39;");return s;}
void noCache(){server.sendHeader("Cache-Control","no-store");server.sendHeader("X-Frame-Options","DENY");server.sendHeader("X-Content-Type-Options","nosniff");}
const char PAGE[] PROGMEM=R"HTML(<!doctype html><html><head><meta name="viewport" content="width=device-width, initial-scale=1"><title>Generator gateway</title><style>body{font:17px system-ui;max-width:760px;margin:24px auto;padding:16px;background:#eef3f8}button{padding:14px;margin:6px}pre{white-space:pre-wrap;background:white;padding:16px}.warn{color:#963600}</style></head><body><h1>Generator gateway</h1><p class="warn">Run request only. Controller and ATS retain protection and transfer control. STOP withdraws this request, not an emergency stop.</p><pre id="state">Connecting...</pre><button onclick="command('start')">Request RUN (30 min maximum)</button><button onclick="command('stop')">Withdraw request</button><p id="result"></p><p>Fuel is approximate sender level, not litres. Low fuel warning at 20%; monitoring only, no automatic engine stop. A stuck float may not be detected.</p><h2>Recent events (lost on reset)</h2><pre id="logs"></pre><p>Keep this page open while requesting RUN. Loss of this page/network withdraws the request within about 20 seconds. No automatic restart.</p><p>Use LAN or a router VPN only. Never forward this web port to the internet.</p><script>
const token='TOKEN_VALUE';let alive=false,lastState='',lastLog='';
async function command(action){try{let r=await fetch('/command',{method:'POST',headers:{'Content-Type':'application/x-www-form-urlencoded'},body:new URLSearchParams({token,action})});let text=await r.text();document.getElementById('result').textContent=text;if(r.ok)alive=action==='start';}catch(e){alive=false;document.getElementById('result').textContent='Network lost; status is stale.';}}
async function poll(){try{let r=await fetch('/status',{cache:'no-store'});if(!r.ok)throw Error();let s=await r.json();let text='Remote key: '+(s.key?'ENABLED':'OFF')+'\nRunning contact: '+(s.running?'CLOSED / asserted':'OPEN / not asserted')+'\nAlarm contact: '+(s.alarm?'CLOSED / asserted':'OPEN / not asserted')+'\nMains available contact: '+(s.mains?'CLOSED / asserted':'OPEN / not asserted')+'\nDiesel level (approx.): '+(s.fuel_pct===null?'UNKNOWN':s.fuel_pct+'%')+'\nFuel status: '+s.fuel_status+'\nRun request: '+(s.request?'ON':'OFF')+'\nLease remaining: '+s.lease+' s\nRun limit remaining: '+s.remaining+' s\nUptime: '+s.uptime+' s';if(text!==lastState){document.getElementById('state').textContent=text;lastState=text;}if(s.log!==lastLog){document.getElementById('logs').textContent=s.log;lastLog=s.log;}if(!s.request)alive=false;}catch(e){document.getElementById('state').textContent='OFFLINE - last status is not current. Check generator locally.';lastState='';}}
setInterval(poll,2000);setInterval(async()=>{if(alive){try{let r=await fetch('/heartbeat',{method:'POST',headers:{'Content-Type':'application/x-www-form-urlencoded'},body:new URLSearchParams({token})});if(!r.ok)alive=false;}catch(e){alive=false;}}},5000);poll();
</script></body></html>)HTML";
void routes(){
 server.on("/",HTTP_GET,[]{if(!auth())return;noCache();if(setupMode){String page="<!doctype html><meta name='viewport' content='width=device-width'><h1>Generator gateway setup</h1><p>Run output is disabled during setup. Use your private 2.4 GHz Wi-Fi.</p><form method='POST' action='/configure'><input type='hidden' name='token' value='"+csrf+"'><p>Wi-Fi name <input name='ssid' required maxlength='32'></p><p>Wi-Fi password <input name='wifi' type='password' maxlength='63'></p><p>New dashboard password (12+ characters) <input name='admin' type='password' minlength='12' maxlength='63' required></p><button>Save and restart</button></form>";server.send(200,"text/html",page);}else{String page=FPSTR(PAGE);page.replace("TOKEN_VALUE",csrf);server.send(200,"text/html",page);}});
 server.on("/configure",HTTP_POST,[]{if(!postAuth())return;if(!setupMode){server.send(403,"text/plain","Setup mode only");return;}String s=server.arg("ssid"),p=server.arg("wifi"),a=server.arg("admin");if(s.length()<1||s.length()>32||p.length()>63||(p.length()>0&&p.length()<8)||a.length()<12||a.length()>63){server.send(400,"text/plain","Check Wi-Fi and password lengths.");return;}prefs.putString("ssid",s);prefs.putString("wifi",p);prefs.putString("admin",a);server.send(200,"text/plain","Saved. Reconnecting. Find the gateway address in serial output or your router's client list.");restartAt=millis()+1500;});
 server.on("/status",HTTP_GET,[]{if(!auth())return;noCache();uint32_t now=millis();String logs;for(int i=0;i<logCount;i++){if(i)logs+="\\n";String e=events[(logHead+24-logCount+i)%24];e.replace("\\","\\\\");e.replace("\"","\\\"");logs+=e;}uint32_t lease=requested && now-leaseAt<LEASE_MS?(LEASE_MS-(now-leaseAt))/1000:0;uint32_t remain=requested && now-startAt<MAX_RUN_MS?(MAX_RUN_MS-(now-startAt))/1000:0;String json="{\"fuel_pct\":"+(fuelPercent<0?String("null"):String(fuelPercent))+",\"fuel_status\":\""+fuelState+"\",\"fuel_ohms\":"+String(fuelOhms,1)+",\"key\":"+String(key.closed?"true":"false")+",\"running\":"+String(running.closed?"true":"false")+",\"alarm\":"+String(alarmContact.closed?"true":"false")+",\"mains\":"+String(mainsContact.closed?"true":"false")+",\"request\":"+String(requested?"true":"false")+",\"lease\":"+String(lease)+",\"remaining\":"+String(remain)+",\"uptime\":"+String(now/1000)+",\"log\":\""+logs+"\"}";server.send(200,"application/json",json);});
 server.on("/command",HTTP_POST,[]{if(!postAuth())return;String action=server.arg("action");if(action=="stop"){stopRequest("Operator withdrew run request");server.send(200,"text/plain","Run request OFF. Engine may continue under controller/ATS control.");}else if(action=="start"){if(!safeToStart()){server.send(409,"text/plain","Blocked: check key, alarm and Wi-Fi. Setup mode cannot start.");return;}if(!requested){startAt=millis();missingAt=millis();requested=true;digitalWrite(RELAY_PIN,HIGH);logEvent("Operator requested RUN");}leaseAt=millis();server.send(200,"text/plain","RUN requested; this does not confirm engine running.");}else server.send(400,"text/plain","Unknown command");});
 server.on("/heartbeat",HTTP_POST,[]{if(!postAuth())return;if(requested&&safeToStart()){leaseAt=millis();server.send(200,"text/plain","Renewed");}else server.send(409,"text/plain","No active run request");});
 server.onNotFound([]{server.send(404,"text/plain","Not found");});server.begin();
}
void setup(){
 digitalWrite(RELAY_PIN,LOW);pinMode(RELAY_PIN,OUTPUT);
 pinMode(FUEL_PIN,INPUT);analogReadResolution(12);analogSetPinAttenuation(FUEL_PIN,ADC_11db);
 Serial.begin(115200);running.begin();alarmContact.begin();mainsContact.begin();key.begin();
 prefs.begin("generator",false);
 setupPassword=prefs.getString("setup","");if(setupPassword.length()<16){char secret[25];snprintf(secret,sizeof(secret),"%08lx%08lx%08lx",(unsigned long)esp_random(),(unsigned long)esp_random(),(unsigned long)esp_random());setupPassword=secret;prefs.putString("setup",setupPassword);}
 char tok[33];snprintf(tok,sizeof(tok),"%08lx%08lx%08lx%08lx",(unsigned long)esp_random(),(unsigned long)esp_random(),(unsigned long)esp_random(),(unsigned long)esp_random());csrf=tok;
 ssid=prefs.getString("ssid","");wifiPassword=prefs.getString("wifi","");adminPassword=prefs.getString("admin",setupPassword);
 // USB serial recovery is local only and requires the physical key OFF.
 setupMode=ssid.isEmpty();
 if(setupMode){adminPassword=setupPassword;WiFi.mode(WIFI_AP);WiFi.softAP("Generator-Setup",setupPassword.c_str());Serial.println("SETUP AP: Generator-Setup");Serial.println("Setup Wi-Fi and admin password: "+setupPassword);Serial.println("Open http://192.168.4.1 ; username admin.");}
 else{WiFi.mode(WIFI_STA);WiFi.setAutoReconnect(true);WiFi.begin(ssid.c_str(),wifiPassword.c_str());Serial.println("Connecting to saved Wi-Fi; no run request restored.");}
 Serial.println("Local recovery: key OFF, send SETUP followed by newline over USB serial at 115200 baud.");
 routes();logEvent("Boot: run request OFF");
}
void loop(){
 uint32_t now=millis();
 updateFuel(now);
 if(running.update())logEvent(running.closed?"Running contact asserted":"Running contact not asserted");
 if(alarmContact.update())logEvent(alarmContact.closed?"Alarm contact asserted":"Alarm contact not asserted");
 if(mainsContact.update())logEvent(mainsContact.closed?"Mains available contact asserted":"Mains available contact not asserted");
 if(key.update())logEvent(key.closed?"Remote key ON":"Remote key OFF");
 static bool wasConnected=false;bool online=connected();if(online!=wasConnected){wasConnected=online;if(online){Serial.print("Dashboard: http://");Serial.println(WiFi.localIP());logEvent("Wi-Fi connected");}else logEvent("Wi-Fi disconnected");}
 if(requested){
  if(digitalRead(ENABLE_PIN)!=LOW)stopRequest("Key OFF: request withdrawn");
  else if(digitalRead(ALARM_PIN)==LOW)stopRequest("Alarm: request withdrawn");
  else if(!online)stopRequest("Wi-Fi lost: request withdrawn");
  else if(now-leaseAt>=LEASE_MS)stopRequest("Dashboard lease expired: request withdrawn");
  else if(now-startAt>=MAX_RUN_MS)stopRequest("30 minute limit: request withdrawn");
  else {if(running.closed)missingAt=now;else if(now-missingAt>=FEEDBACK_MS)stopRequest("No running feedback for 90 seconds: request withdrawn");}
 }
 static String serialCommand;
 while(Serial.available()){
  char c=Serial.read();
  if(c=='\n'){
   serialCommand.trim();
   if(serialCommand=="SETUP" && digitalRead(ENABLE_PIN)==HIGH){stopRequest("Local setup recovery");prefs.remove("ssid");restartAt=millis()+500;}
   serialCommand="";
  }else if(serialCommand.length()<32)serialCommand+=c;
 }
 server.handleClient();
 if(restartAt && (int32_t)(millis()-restartAt)>=0){stopRequest("Restart");ESP.restart();}
 delay(2);
}