Writing large Peer to Peer NFC messages from Arduino

generate_ndef_bytes.js

// generate raw NDEF bytes for cut and paste into an Arduino sketch
//
// $ npm install ndef
// $ node generate_ndef_bytes.js 10
// cut and paste the output into your Arduino sketch

var ndef = require('ndef');
var NUM_CHARS = process.argv[2] || 226;

var data = "";
for (var i = 0; i < NUM_CHARS; i++) {
  data += "a";
}

var record = ndef.textRecord(data);
var bytes = ndef.encodeMessage([record]);

console.log('// NDEF message with ' + NUM_CHARS + ' char string (TNF WELL_KNOWN, RTD Text)')
console.log('uint8_t ndef_buffer[] = {' + bytes.join() + '};');

P2P_Send_LongRecord.ino

// Sends a NDEF Message to a Peer
// Requires SPI. Tested with Seeed Studio NFC Shield v2

#include "SPI.h"
#include "PN532_SPI.h"
#include "snep.h"
#include "NdefMessage.h"

#define TEXT_SIZE 226
#define LANGUAGE_ENCODING_SIZE 3
#define PAYLOAD_SIZE (TEXT_SIZE + LANGUAGE_ENCODING_SIZE)
#define MESSAGE_ENCODING_SIZE 4
#define NDEF_BUFFER_SIZE (PAYLOAD_SIZE + MESSAGE_ENCODING_SIZE)

PN532_SPI pn532spi(SPI, 10);
SNEP nfc(pn532spi);
uint8_t ndefBuf[NDEF_BUFFER_SIZE];
int messageSize;

void setup() {
  Serial.begin(9600);
  Serial.println("NFC Peer to Peer Example - Send Message");

  NdefMessage message = NdefMessage();

  // manually create a record, so Uno doesn't run out of memory
  NdefRecord record = NdefRecord();
  record.setTnf(TNF_WELL_KNOWN);
  
  uint8_t recordType[] = { 0x54 }; // "T" Text Record
  record.setType(recordType, sizeof(recordType));
  
  uint8_t payload[PAYLOAD_SIZE];
  // fill buffer with the character "b"
  memset(payload, 0x62, sizeof(payload));
  // manually add language encoding for TNF_WELL_KNOWN RTD_TEXT
  payload[0] = 0x02;
  payload[1] = 0x65; // e
  payload[2] = 0x6e; // n
  record.setPayload(payload, sizeof(payload));
  message.addRecord(record);

  messageSize = message.getEncodedSize();
  if (messageSize != NDEF_BUFFER_SIZE) {
    Serial.println("Buffer size is incorrect!");
    while (1) {
    }
  }
  
  message.encode(ndefBuf);
}

void loop() {
  Serial.println("Send a message to Peer");
  Serial.println(messageSize);
  
  if (0 >= nfc.write(ndefBuf, messageSize)) {
    Serial.println("Failed");
  } else {
    Serial.println("Success");
  }

  delay(3000);
}

P2P_Send_LongString.ino

// Sends a NDEF Message to a Peer
// Requires SPI. Tested with Seeed Studio NFC Shield v2
// Requires Arduino Due (or maybe another board with lots of memory)

#include "SPI.h"
#include "PN532_SPI.h"
#include "snep.h"
#include "NdefMessage.h"

PN532_SPI pn532spi(SPI, 10);
SNEP nfc(pn532spi);
uint8_t ndefBuf[233];
int messageSize;

void setup() {
    Serial.begin(9600);
    Serial.println("NFC Peer to Peer Example - Send Message");

    NdefMessage message = NdefMessage();
    // 226 character string creates 233 byte message
    // need to run on a Due, since encoding the message run an Uno out of memory
    message.addTextRecord("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
    
    messageSize = message.getEncodedSize();
    if (messageSize > sizeof(ndefBuf)) {
        Serial.println("ndefBuf is too small");
        while (1) {
        }
    }

    message.encode(ndefBuf);
}

void loop() {
    Serial.println("Send a message to Peer");
    Serial.println(messageSize);
    
    if (0 >= nfc.write(ndefBuf, messageSize)) {
        Serial.println("Failed");
    } else {
        Serial.println("Success");
    }

    delay(3000);
}

P2P_Send_Raw.ino

// Sends a NDEF Message to a Peer
// Requires SPI. Tested with Seeed Studio NFC Shield v2

// Send Raw Bytes to see if the size limit of PN532

#include "SPI.h"
#include "PN532_SPI.h"
#include "snep.h"

PN532_SPI pn532spi(SPI, 10);
SNEP nfc(pn532spi);

// WELL_KNOWN T "hello"
//uint8_t ndef_buffer[] = {209, 1, 8, 84, 2, 101, 110, 104, 101, 108, 108, 111};

// 226 char string works, 227 char string fails

// NDEF message with 226 char string (TNF WELL_KNOWN, RTD Text)
uint8_t ndef_buffer[] = {209,1,229,84,2,101,110,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97};

// NDEF message with 227 char string (TNF WELL_KNOWN, RTD Text)
// uint8_t ndef_buffer[] = {209,1,230,84,2,101,110,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97,97};

void setup() {
    Serial.begin(9600);
    Serial.println("NFC Peer to Peer Example - Send Message");
}

void loop() {
    Serial.println("Send a message to Peer");
    Serial.println(sizeof(ndef_buffer));
    
    if (0 >= nfc.write(ndef_buffer, sizeof(ndef_buffer))) {
        Serial.println("Failed");
    } else {
        Serial.println("Success");
    }

    delay(3000);
}