My teacher just gave me a NFC tag v1.0 for a project. I have to use my phone to unlock a door.

I searched on internet and I just found this code:

#include "NfcTag.h" #include <Wire.h>  NfcTag nfcTag; int led = 5; bool flag = false; bool preFlag = false; void setup(){   Serial.begin(9600);   pinMode(led,OUTPUT);   nfcTag.init(); }  void loop(){   flag = nfcTag.readByte(EEPROM_I2C_LENGTH-1) == 0xff?true:false;   if(flag != preFlag){     Serial.println("get remote NFC control signal!");     if(flag == true){       Serial.println("led will light up!");       digitalWrite(led,HIGH);     }else{       Serial.println("led will turn dark!");       digitalWrite(led,LOW);     }     preFlag = flag;   }   delay(5*1000); } 

This come from their wiki: http://wiki.seeed.cc/Grove-NFC_Tag/

I can connect with the phone and use it to change blocks. The problem is that when I try it, the LED just doesn’t work at all. I tried the LED and he is working, I also tried the Digital pin on the Arduino UNO with the LED and it works as well. Also, the monitor doesn’t show any off those printLn.

I used this way to connect them:

SCL – RX

SDA – TX

GND – GND

5V – VCC

I also used a code to debug, but no matter what address I use to readByte, I will always get the number 127 even after using the phone to change it with the app.

#include "NfcTag.h" #include <Wire.h>  NfcTag nfcTag; bool flag = false; bool preFlag = false;  void setup() {   // put your setup code here, to run once:   Serial.begin(115200);   Serial.println("starting sequence");   nfcTag.init(); }  void loop() {   // put your main code here, to run repeatedly:   Serial.println("checking for nfc");   //flag = nfcTag.readByte(EEPROM_I2C_LENGTH-1) == 0xff?true:false;   //Serial1.println(flag);   Serial.println(nfcTag.getICNumber());   Serial.println(nfcTag.getAFI());   Serial.println(nfcTag.getRFU());   Serial.println(nfcTag.getMemoryVolume());   Serial.println("result:");   Serial.println(nfcTag.readByte(EEPROM_I2C_LENGTH-1)); //I tried changeing manualy the value, but the output still 127.    delay(2000);  } 

Output:

checking for nfc 127 127 32639 8355711 result: 127 

If I could put the LED working, I have already a transistor with a power converter on the exit of the pin5, so the door can be unlocked.

By the way, I don’t know why sometimes the NFC doesn’t work and after some tries it start working again.

Any help will be appreciate 🙂 Thanks.