Merge pull request 'nfc-module' (#10) from nfc-module into main

Reviewed-on: #10
Reviewed-by: Matthias Blankertz <matthias@blankertz.org>

software/boards/RPI_PICO_W/manifest.py

@@ -9,7 +9,10 @@ module("rp2_neopixel.py", "../../src")
 require("sdcard")
 require("aiorepl")
 
+# Third party modules
 module("mfrc522.py", "../../lib/micropython-mfrc522/")
 module("microdot.py", "../../lib/microdot/src/microdot/")
 
+# TonberryPico modules
 module("audiocore.py", "../../src/audiocore")
+package("nfc", base_path="../../src/")

software/src/nfc/__init__.py

@@ -0,0 +1,7 @@
+'''
+SPDX-License-Identifier: MIT
+Copyright (c) 2025 Stefan Kratochwil (Kratochwil-LA@gmx.de)
+'''
+from nfc.nfc import Nfc
+
+__all__ = ['Nfc']

software/src/nfc/nfc.py

@@ -0,0 +1,76 @@
+'''
+SPDX-License-Identifier: MIT
+Copyright (c) 2025 Stefan Kratochwil (Kratochwil-LA@gmx.de)
+'''
+
+import asyncio
+import time
+
+from mfrc522 import MFRC522
+
+
+class Nfc:
+    '''
+    This class implements an asyncio task which continuously polls the mfrc522 nfc reader. If a new
+    nfc tag was detected, the uid of the tag is stored alongside with the current system time. This
+    information can be retrieved again.
+
+    Usage example:
+
+    import asyncio
+    from nfc import Nfc
+
+    async def main():
+        n = Nfc()
+        while True:
+            await asyncio.sleep_ms(500)
+            print(f'{n.get_last_uid()}')
+
+    asyncio.run(main())
+    '''
+    def __init__(self, reader: MFRC522):
+        self.reader = reader
+        self.last_uid = None
+        self.last_uid_timestamp = None
+        self.task = asyncio.create_task(self._reader_poll_task())
+
+    @staticmethod
+    def uid_to_string(uid: list):
+        '''
+        Helper function to convert a nfc tag uid to a readable string.
+        '''
+        return '0x' + ''.join(f'{i:02x}' for i in uid)
+
+    async def _reader_poll_task(self, poll_interval_ms: int = 50):
+        '''
+        Periodically polls the nfc reader. Stores tag uid and timestamp if a new tag was found.
+        '''
+        while True:
+            self.reader.init()
+
+            # For now we omit the tag type
+            (stat, _) = self.reader.request(self.reader.REQIDL)
+            if stat == self.reader.OK:
+                (stat, uid) = self.reader.SelectTagSN()
+                if stat == self.reader.OK:
+                    self.last_uid = uid
+                    self.last_uid_timestamp = time.ticks_us()
+
+            await asyncio.sleep_ms(poll_interval_ms)
+
+    def get_last_uid(self):
+        '''
+        Returns the last read nfc tag uid alongside with the timestamp it was stored at.
+        '''
+        return self.last_uid, self.last_uid_timestamp
+
+
+if __name__ == '__main__':
+    async def main():
+        reader = MFRC522(spi_id=1, sck=10, miso=12, mosi=11, cs=13, rst=9, tocard_retries=20)
+        n = Nfc(reader=reader)
+        while True:
+            await asyncio.sleep_ms(500)
+            print(f'{n.get_last_uid()}')
+
+    asyncio.run(main())