ESP8266 PN532 NDEF reader/writer

Explanation.md

Explanation:

• Setup WiFi and PN532: Connect to the WiFi network and initialize the PN532 NFC reader.
• Reading NFC Tags: The readNFC function reads NFC tags, decodes the URI and text fields, and sends them to a specified HTTP endpoint.
• HTTP Server: The ESP8266 hosts an HTTP server with a /writeNDEF endpoint to receive JSON payloads to write to NFC tags.
• Writing to NFC Tags: The writeNDEFToTag function writes the received URI and description to a new NFC tag.

Notes:

• Ensure you replace YOUR_SSID, YOUR_PASSWORD, and http://yourserver.com/endpoint with your actual WiFi credentials and server URL.
• The code uses NdefRecord for creating URI and text records. Adjust as needed based on your NFC library's API.

main.cpp

#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#include <ESP8266WebServer.h>
#include <ArduinoJson.h>
#include <Wire.h>
#include <Adafruit_PN532.h>
#include <NdefMessage.h>
#include <Ndef.h>
#include <NfcAdapter.h>

// Replace these with your network credentials
const char* ssid = "YOUR_SSID";
const char* password = "YOUR_PASSWORD";

// Your server endpoint to send the read tag data
const char* serverUrl = "http://yourserver.com/endpoint";

// PN532 configuration
#define SDA_PIN 4  // D2 on NodeMCU
#define SCL_PIN 5  // D1 on NodeMCU

Adafruit_PN532 nfc(SDA_PIN, SCL_PIN);
NfcAdapter nfcAdapter(nfc);

ESP8266WebServer server(80);

void setup() {
  Serial.begin(115200);
  delay(10);

  // Connect to Wi-Fi
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());

  // Initialize NFC reader
  nfc.begin();
  uint32_t versiondata = nfc.getFirmwareVersion();
  if (!versiondata) {
    Serial.print("Didn't find PN53x board");
    while (1);
  }
  
  nfc.SAMConfig();
  nfcAdapter.begin();

  // Setup web server endpoints
  server.on("/writeNDEF", HTTP_POST, handleWriteNDEF);
  server.begin();
  Serial.println("HTTP server started");
}

void loop() {
  server.handleClient();
  readNFC();
}

void readNFC() {
  if (nfcAdapter.tagPresent()) {
    NfcTag tag = nfcAdapter.read();
    Serial.println("Found an NFC tag");

    String uri = "";
    String description = "";

    if (tag.hasNdefMessage()) {
      NdefMessage ndefMessage = tag.getNdefMessage();
      for (int i = 0; i < ndefMessage.getRecordCount(); i++) {
        NdefRecord record = ndefMessage.getRecord(i);
        if (record.getType() == "U") {
          uri = record.getUri();
        } else if (record.getType() == "T") {
          description = record.getText();
        }
      }

      if (!uri.isEmpty() && !description.isEmpty()) {
        sendToServer(uri, description);
      }
    }
    delay(1000); // Add a delay to prevent reading the same tag multiple times
  }
}

void sendToServer(String uri, String description) {
  if (WiFi.status() == WL_CONNECTED) {
    HTTPClient http;
    http.begin(serverUrl);
    http.addHeader("Content-Type", "application/json");

    StaticJsonDocument<256> doc;
    doc["uri"] = uri;
    doc["description"] = description;
    String requestBody;
    serializeJson(doc, requestBody);

    int httpResponseCode = http.POST(requestBody);

    if (httpResponseCode > 0) {
      String response = http.getString();
      Serial.println(httpResponseCode);
      Serial.println(response);
    } else {
      Serial.print("Error on sending POST: ");
      Serial.println(httpResponseCode);
    }

    http.end();
  }
}

void handleWriteNDEF() {
  if (server.hasArg("plain") == false) {
    server.send(400, "application/json", "{\"error\":\"Invalid request\"}");
    return;
  }

  String body = server.arg("plain");
  StaticJsonDocument<256> doc;
  DeserializationError error = deserializeJson(doc, body);

  if (error) {
    server.send(400, "application/json", "{\"error\":\"Invalid JSON\"}");
    return;
  }

  const char* uri = doc["uri"];
  const char* description = doc["description"];

  if (writeNDEFToTag(uri, description)) {
    server.send(200, "application/json", "{\"status\":\"Tag written successfully\"}");
  } else {
    server.send(500, "application/json", "{\"error\":\"Failed to write tag\"}");
  }
}

bool writeNDEFToTag(const char* uri, const char* description) {
  NdefMessage message = NdefMessage();
  
  NdefRecord uriRecord = NdefRecord(NdefRecord::Uri, uri);
  NdefRecord textRecord = NdefRecord(NdefRecord::Text, description);

  message.addRecord(uriRecord);
  message.addRecord(textRecord);

  bool success = nfcAdapter.write(message);
  return success;
}