/*
  Arduino | Coding-help
  NeoPixel Ring stops MFRC522 RFID reader from reading

  hhero - Sunday, April 5, 2026 8:54 AM
  Hey everyone, I’m working on an Arduino Mega
  + MFRC522 RFID reader + 24-LED NeoPixel ring setup
  and I’m running into a weird timing issue I can’t solve.
*/

#include <SPI.h>
#include <MFRC522.h>
#include <Adafruit_NeoPixel.h>

#define RST_PIN 5
#define SS_PIN 53

#define IDLE_LED 7
#define CORRECT_LED 8
#define WRONG_LED 6

#define PIXEL_PIN 9
#define NUMPIXELS 24

MFRC522 mfrc522(SS_PIN, RST_PIN);
Adafruit_NeoPixel ring(NUMPIXELS, PIXEL_PIN, NEO_GRB + NEO_KHZ800);

// Correct UID
//byte correctUID[] = {0xA1, 0x96, 0x69, 0x06};
byte correctUID[] = {0x01, 0x02, 0x03, 0x04};

byte uidLength = 4;


// track current color
uint8_t currentR = 255;
uint8_t currentG = 150;
uint8_t currentB = 0;

uint16_t chaseIndex = 0;
unsigned long lastFrame = 0;

void runIdleAnimation() {

  if (millis() - lastFrame < 80) return;

  lastFrame = millis();

  for (int i = 0; i < NUMPIXELS; i++) {

    ring.setPixelColor(i, ring.Color(10, 5, 0));

  }

  ring.setPixelColor(chaseIndex, ring.Color(255, 150, 0));

  ring.show();

  chaseIndex++;

  if (chaseIndex >= NUMPIXELS) chaseIndex = 0;

}


// smooth fade function
void fadeToColor(uint8_t r, uint8_t g, uint8_t b) {

  int steps = 40;

  for (int i = 0; i <= steps; i++) {

    uint8_t newR = currentR + (r - currentR) * i / steps;
    uint8_t newG = currentG + (g - currentG) * i / steps;
    uint8_t newB = currentB + (b - currentB) * i / steps;

    for (int p = 0; p < NUMPIXELS; p++) {

      ring.setPixelColor(p, newR, newG, newB);

    }

    ring.show();
    delay(10);

  }

  currentR = r;
  currentG = g;
  currentB = b;

}


bool compareUID(byte *uid1, byte *uid2) {

  for (byte i = 0; i < uidLength; i++) {

    if (uid1[i] != uid2[i]) return false;

  }

  return true;

}

void setup() {

  Serial.begin(9600);

  SPI.begin();
  mfrc522.PCD_Init();

  pinMode(IDLE_LED, OUTPUT);
  pinMode(CORRECT_LED, OUTPUT);
  pinMode(WRONG_LED, OUTPUT);

  ring.begin();
  ring.show();

  fadeToColor(255, 150, 0);  // start yellow idle

  Serial.println("Plate reader ready.");

}


void loop() {

  digitalWrite(IDLE_LED, HIGH);
  digitalWrite(CORRECT_LED, LOW);
  digitalWrite(WRONG_LED, LOW);

  if (!mfrc522.PICC_IsNewCardPresent()) {

    runIdleAnimation();
    return;
    Serial.println("hi");

  }

  Serial.println("2");

  if (!mfrc522.PICC_ReadCardSerial()) return;


  Serial.println("Tag detected");

  digitalWrite(IDLE_LED, LOW);


  if (compareUID(mfrc522.uid.uidByte, correctUID)) {

    Serial.println("Correct plant");

    digitalWrite(CORRECT_LED, HIGH);

    fadeToColor(0, 255, 0);

  }

  else {

    Serial.println("Wrong plant");

    digitalWrite(WRONG_LED, HIGH);

    fadeToColor(255, 0, 0);

  }


  delay(1500);


  digitalWrite(IDLE_LED, HIGH);
  digitalWrite(CORRECT_LED, LOW);
  digitalWrite(WRONG_LED, LOW);

  fadeToColor(255, 150, 0);


  mfrc522.PICC_HaltA();

}