Home Assistant and NFC Tags

Source: Wikimedia Commons

I am experimenting with NFC Tags and automation on Home Assistant. I have bought a few writeable NFC tags for these experiments. They are cheap, but I wouldn’t say I like wasting them while testing.

Since Flipper Zero can simulate NFC tags, I decided to use it for my tests.

If you want to do the same, here is what you need to do.

Flipper Zero stores NFC Tag data in a plain text file with a .nfc extension. There is a simple command line python script that allows you to write an NFC tag in the Flipper Zero format. Thank you to evilpete for making this available.

#!/usr/bin/env python """     Generates NFC with URL address data and outputs Flipper NFC "save" file     this is a 5 min hack, No Guarantees      ./nfc_gen_url.py https://youtu.be/dQw4w9WgXcQ "Rick Roll" > rickroll.nfc      requires ndeflib      Written By: Peter Shipley github.com/evilpete      From pkg https://github.com/evilpete/flipper_toolbox """  import sys  try:     import ndef except ImportError as e:     print("Failed to import ndef")     print("https://github.com/nfcpy/ndeflib")     sys.exit(0)  # make sure output is utf-8 sys.stdout.reconfigure(encoding='utf-8')  # for debuging verbose = 0  nfc_header = """Filetype: Flipper NFC device Version: 2 # generated with flipper_toolbox Device type: NTAG215 # UID, ATQA and SAK are common for all formats UID: 04 10 56 01 74 48 03 ATQA: 44 00 SAK: 00 # Mifare Ultralight specific data Signature: A5 80 A4 CC A0 C3 A1 F6 8B BE 6F EE 83 A6 B9 EE 36 F8 FB C8 14 5A 23 AA 29 DB 78 56 07 B9 6B 92 Mifare version: 00 04 04 02 01 00 11 03 Counter 0: 0 Tearing 0: 00 Counter 1: 0 Tearing 1: 00 Counter 2: 0 Tearing 2: 00 Pages total: 135 """  data_static = [     0x04, 0x10, 0x56, 0xCA,     # 01 serial number     0x01, 0x74, 0x48, 0x03,     # 02 serial number     0x3E, 0x48, 0x00, 0x00,     # 03 serial number, internal, lock bytes, lock bytes     0xE1, 0x10, 0x3E, 0x00,     # 04 Capability Container ]  conf_pages = [     0x00, 0x00, 0x00, 0xBD,      # 130     0x04, 0x00, 0x00, 0xFF,      # 131     0x00, 0x05, 0x00, 0x00,      # 132     0x00, 0x00, 0x00, 0x00,      # 133     0x00, 0x00, 0x00, 0x00,      # 134 ]   def print_nfc_sub(t_data, file=sys.stdout):      print(nfc_header, end='', file=file)      p = 0     for x in range(0, 540, 4):         print(f"Page {p}: {t_data[x]:02X} {t_data[x + 1]:02X} "               f"{t_data[x + 2]:02X} {t_data[x + 3]:02X}", file=file)         p = p + 1   def gen_nfc_sub(tag_data):      tag_message = []     data_list = []      for x in tag_data:         if x[0] == 'txt':             tag_message.append(ndef.TextRecord(x[1], "en"))         elif x[0] == 'url':             tag_message.append(ndef.UriRecord(x[1]))          if verbose:             print(x, file=sys.stderr)             print(tag_message[-1:], file=sys.stderr)      buf = b"".join((ndef.message_encoder(tag_message)))      m_len = len(buf)      if verbose:         print("buf", m_len, hex(m_len), buf, file=sys.stderr)      data_list.extend(data_static)     data_list.append(3)         # Message Flags     if m_len < 255:         data_list.append(m_len)         # Type Length     else:         data_list.append(0xFF)         lenStr = hex(m_len)[2:].rjust(4, "0")         data_list.append(int(lenStr[0:2], 16))         data_list.append(int(lenStr[2:4], 16))     data_list.extend(list(buf))      data_list.append(0xFE)      # end of Data      data_len = len(data_list)      if verbose:         print("data_list", data_len, data_list, file=sys.stderr)      x = 520 - data_len     data_list.extend([0] * x)     data_list.extend(conf_pages)      return data_list   # url_str = "https://youtu.be/dQw4w9WgXcQ" # title_str = "Rick Roll"  if __name__ == '__main__':      arg_data = []      for a in sys.argv[1:]:         if a.startswith("http"):             arg_data.append(("url", a))         else:             arg_data.append(("txt", a))      if not arg_data:         print("requires at least one URL argument\n"               "Please provide URL and optional Title\n\n"               f"{sys.argv[0]} : https://some.url  'Title'")         sys.exit()      nfc_data = gen_nfc_sub(arg_data)      print_nfc_sub(nfc_data)      sys.exit()  

Copy the script on your computer (e.g. nfcdata.py) and run it:

python3 nfcdata.py "Test data" 

This will create a file that you can upload to your Flipper Zero using the qFlipper desktop application.

You will now be able to emulate the tag on the Flipper Zero.

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