XLChain Jun, 2018

#include <Adafruit_NeoPixel.h>

const int LED = 1;
const int GND = 2;

const int NUMPIXELS = 1;
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, LED, NEO_GRB + NEO_KHZ800);

// the setup routine runs once when you press reset:
void setup() {
  // init digital ground
  pinMode(GND, OUTPUT);
  digitalWrite(GND, LOW);
  // initialize the digital pin as an output.
  pinMode(LED, OUTPUT);
  pixels.begin();
  showGreenLED(); 
}

// the loop routine runs over and over again forever:
void loop() { 
}

void showGreenLED() {
    pixels.setPixelColor(0, pixels.Color(0,150,0)); // Moderately bright green color.
    pixels.show(); // This sends the updated pixel color to the hardware.
}

#include <Adafruit_NeoPixel.h>

const int LASERSENSOR = 0;
const int LED = 1;
const int GND0 = 2;
const int GND1 = 3;
const int USB = 4;
int SensorReading = HIGH;

const int NUMPIXELS = 1;
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, LED, NEO_GRB + NEO_KHZ800);

// the setup routine runs once when you press reset:
void setup() {
  // set up digital ground and 5v
  pinMode(GND0, OUTPUT);
  pinMode(GND1, OUTPUT);
  pinMode(USB, OUTPUT);
  digitalWrite(GND0, LOW);
  digitalWrite(GND1, LOW);
  digitalWrite(USB, HIGH);
  // initialize the digital pin as an output.
  pinMode(LED, OUTPUT);
  pinMode(LASERSENSOR, INPUT);
  pixels.begin();
}

// the loop routine runs over and over again forever:
void loop() {
  SensorReading = digitalRead(LASERSENSOR);
  if(SensorReading == LOW) {  // init status
    showWhiteLED();                        
  } else {  // when chain pass through
    showGreenLED();                    
  }
}

void showWhiteLED() {
    pixels.setPixelColor(0, pixels.Color(255,255,255)); 
    pixels.show();
}

void showGreenLED() {
    pixels.setPixelColor(0, pixels.Color(0,150,0)); // Moderately bright green color.
    pixels.show(); // This sends the updated pixel color to the hardware.
}

/*
   --------------------------------------------------------------------------------------------------------------------
   Example sketch/program showing how to read new NUID from a PICC to serial.
   --------------------------------------------------------------------------------------------------------------------
    pin layout used:
    RFID Reader:
   -----------------------------------
               MFRC522      Arduino
               Reader/PCD   Uno/101
   Signal      Pin          Pin
   -----------------------------------
   RST/Reset   RST          9
   SPI SS      SDA(SS)      10
   SPI MOSI    MOSI         11 / ICSP-4
   SPI MISO    MISO         12 / ICSP-1
   SPI SCK     SCK          13 / ICSP-3

   Neopixel strip:
   ------------------------------------
   VCC         VCC          5V
   CND         GND          GND
   DIN         DI           8
*/

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

#define PIXEL_PIN   8    // Digital IO pin connected to the NeoPixels.

#define PIXEL_COUNT 5   //number of pixel on the strip

constexpr uint8_t RST_PIN = 9;     // Configurable, see typical pin layout above
constexpr uint8_t SS_PIN = 10;     // Configurable, see typical pin layout above

MFRC522 rfid(SS_PIN, RST_PIN); // Instance of the class
int count = 0;// to delay the connection

// Parameter 1 = number of pixels in strip,  neopixel stick has 8
// Parameter 2 = pin number (most are valid)
// Parameter 3 = pixel type flags, add together as needed:
//   NEO_RGB     Pixels are wired for RGB bitstream
//   NEO_GRB     Pixels are wired for GRB bitstream, correct for neopixel stick
//   NEO_KHZ400  400 KHz bitstream (e.g. FLORA pixels)
//   NEO_KHZ800  800 KHz bitstream (e.g. High Density LED strip), correct for neopixel stick
Adafruit_NeoPixel strip = Adafruit_NeoPixel(PIXEL_COUNT, PIXEL_PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  Serial.begin(9600);
  SPI.begin(); // Init SPI bus
  rfid.PCD_Init(); // Init MFRC522
  strip.begin();
  strip.show(); // Initialize all pixels to 'off'
}

void loop() {
  // Looking for RFID tag
  byte bufferATQA[2];
  byte bufferSize = sizeof(bufferATQA);
  MFRC522::StatusCode result = rfid.PICC_RequestA(bufferATQA, &bufferSize);

  //if tag found, showing running green pixels for 5 times, then steady green display
  if ( result == 0) {
    if (count < 5) {
      colorWipe(strip.Color(0, 255, 0), 5000); // green
      colorWipe(strip.Color(0, 0, 0), 5000);  //running mode
      count ++;
    }
    else {
      colorWipe(strip.Color(0, 255, 0), 5000);
    }

    rfid.PCD_StopCrypto1(); // Stop encryption on PCD

    //reopen the antenna to guarantee the reading success
    rfid.PCD_AntennaOff();
    rfid.PCD_AntennaOn();
  }
  //if no tag found, show only one white pixel and if the tag removed, show a running white mode one tiems and then back to one white pixel display.
  else {
    if (count >= 5) {
      colorWipe(strip.Color(127, 127, 127), 5000); // white
    }
    strip.setPixelColor(0, strip.Color(127, 127, 127)); // bright color.
    strip.setPixelColor(1, strip.Color(0, 0, 0)); // off
    strip.setPixelColor(2, strip.Color(0, 0, 0)); // off
    strip.setPixelColor(3, strip.Color(0, 0, 0)); // off
    strip.setPixelColor(4, strip.Color(0, 0, 0)); // off
    strip.show(); // This sends the updated pixel color to the hardware.
    count = 0;
  }
  delay(500);
}

// Fill the dots one after the other with a color
void colorWipe(uint32_t c, uint8_t wait) {
  for (uint16_t i = 0; i < strip.numPixels(); i++) {
    strip.setPixelColor(i, c);
    strip.show();
    delay(wait);
  }
}