ESP32-CAM QR Code Scanner

// ESP32-CAM QR Scanner - Advanced (MQTT access control)
#include "esp_camera.h"
#include <quirc.h>
#include <WiFi.h>
#include <PubSubClient.h>
#include <ArduinoJson.h>
#include "SD_MMC.h"
#include <time.h>

#define RELAY  12
#define LED_G  13
#define LED_R  15
#define BUZZER 14
#define PWDN_GPIO_NUM 32
// ... other pin defines

const char* SSID="YourSSID", *PASS="YourPass";
const char* MQTT_HOST="192.168.1.100";
const char* TOPIC_SCAN  ="qr/scan";
const char* TOPIC_RESULT="qr/result";

WiFiClient wifiClient;
PubSubClient mqtt(wifiClient);
struct quirc *qr;

bool waitingResult=false;
String pendingPayload="";

void grantAccess(){
  digitalWrite(LED_G,HIGH); digitalWrite(RELAY,LOW); // relay active LOW
  tone(BUZZER,1000,200);
  delay(3000);
  digitalWrite(LED_G,LOW); digitalWrite(RELAY,HIGH);
}

void denyAccess(){
  digitalWrite(LED_R,HIGH);
  tone(BUZZER,400,500);
  delay(1000);
  digitalWrite(LED_R,LOW);
}

void mqttCallback(char* topic, byte* payload, unsigned int len){
  String result((char*)payload,len);
  if(result=="ALLOW") grantAccess();
  else denyAccess();
  waitingResult=false;
  // Log to SD
  time_t now=time(nullptr); String ts=ctime(&now); ts.trim();
  File f=SD_MMC.open("/access.csv",FILE_APPEND);
  if(f){ f.println(ts+","+pendingPayload+","+result); f.close(); }
}

void setup(){
  Serial.begin(115200);
  pinMode(RELAY,OUTPUT); digitalWrite(RELAY,HIGH); // start locked
  pinMode(LED_G,OUTPUT); pinMode(LED_R,OUTPUT); pinMode(BUZZER,OUTPUT);
  // camera init GRAYSCALE QVGA
  WiFi.begin(SSID,PASS);
  while(WiFi.status()!=WL_CONNECTED) delay(500);
  configTime(0,0,"pool.ntp.org");
  SD_MMC.begin();
  mqtt.setServer(MQTT_HOST,1883);
  mqtt.setCallback(mqttCallback);
  qr=quirc_new(); quirc_resize(qr,320,240);
}

void loop(){
  if(!mqtt.connected()){ mqtt.connect("ESP32QR"); mqtt.subscribe(TOPIC_RESULT); }
  mqtt.loop();
  if(waitingResult){ delay(50); return; }

  camera_fb_t *fb=esp_camera_fb_get();
  if(!fb){ delay(50); return; }
  uint8_t *buf=quirc_begin(qr,NULL,NULL);
  memcpy(buf,fb->buf,fb->len);
  quirc_end(qr);
  esp_camera_fb_return(fb);

  int n=quirc_count(qr);
  for(int i=0;i<n;i++){
    struct quirc_code code; struct quirc_data data;
    quirc_extract(qr,i,&code);
    if(quirc_decode(&code,&data)==QUIRC_SUCCESS){
      pendingPayload=(char*)data.payload;
      mqtt.publish(TOPIC_SCAN,pendingPayload.c_str());
      waitingResult=true;
      break;
    }
  }
  delay(100);
}