NFC tag v1.0 & arduino UNO - arduino

Question

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.

Answer 1

The correct connection for the I2C pins is:
SCL - PC5 (Analog A5)
SDA - PC4 (Analog A4)
This part supports Uart communications as you wired it. The link you provided for the part you are using only support I2C and will not work as you wired it.