title: Converting between unsigned long and uint8_t array
body: <p>I am trying to read and write an unsigned long type value to an NFC card.</p>
  
  <p>I am working with the pn532 module, the MifareUltralight card, and the Adafruit library. The mifareultralight_WritePage function seems to accept only an array of type uint8_t which size of 4-byte.</p>
  
  <p>So I want to store a four-byte long type value in a Uint8_t array by one by one and convert a Uint8_t array of 4-byte length into one long type variable.</p>
  
  <pre><code>#include &lt;Adafruit_PN532.h&gt;
  
  ...
  
  uint8_t writeBuffer[4] = { 18, 52, 86, 120 };
  nfc.mifareultralight_WritePage(8, writeBuffer);
  </code></pre>
  
  <pre><code>uint8_t readBuffer[4];
  success = nfc.mifareultralight_ReadPage(i, &amp;readBuffer[0]);
      if (success) {
          nfc.PrintHex(readBuffer, 4);
  }
  </code></pre>