Merge pull request 'micropython-mfrc522' (#4) from micropython-mfrc522 into main

Reviewed-on: #4
Reviewed-by: Matthias Blankertz <matthias@blankertz.org>

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "software/lib/micropython"]
 	path = software/lib/micropython
-	url = ssh://git@git.ka.blankertz.org:2222/TonBERRY/micropython.git
+	url = ../micropython.git
+[submodule "software/lib/micropython-mfrc522"]
+	path = software/lib/micropython-mfrc522
+	url = ../micropython-mfrc522.git

software/boards/RPI_PICO_W/manifest.py

@@ -8,3 +8,5 @@ require("aioble")
 module("rp2_neopixel.py", "../../src")
 require("sdcard")
 require("aiorepl")
+
+module("mfrc522.py", "../../lib/micropython-mfrc522/")

software/src/mfrc522/main.py

@@ -0,0 +1,73 @@
+from mfrc522 import MFRC522
+import asyncio
+import time
+
+delay_sum = 0
+delay_count = 0
+max_delay = 0
+
+
+async def latency_test():
+    global delay_sum
+    global delay_count
+    global max_delay
+    global min_delay
+    min_delay = 0xffffffff
+    await asyncio.sleep_ms(1)
+    while True:
+        for _ in range(2000):
+            before = time.ticks_us()
+            await asyncio.sleep(0)
+            after = time.ticks_us()
+            delay = after - before
+            delay_sum += delay
+            delay_count += 1
+            if delay > max_delay:
+                max_delay = delay
+            if delay < min_delay:
+                min_delay = delay
+            await asyncio.sleep_ms(1)
+        print(f"delay (min / max / avg) [µs]: ({min_delay} / {max_delay} / {delay/delay_sum})")
+
+
+def uid_to_string(uid: list):
+    return '0x' + ''.join(f'{i:02x}' for i in uid)
+
+
+async def get_tag_uid(reader: MFRC522, poll_interval_ms: int = 50) -> list:
+    '''
+    The maximum measured delay with poll_interval_ms=50 and a reader with tocard_retries=5 is
+    15.9 ms:
+        delay (min / max / avg) [µs]: (360 / 15945 / 1.892923e-06)
+
+    The maximum measured delay dropped to 11.6 ms by setting tocard_retries=1:
+        delay (min / max / avg) [µs]: (368 / 11696 / 6.204211e-06)
+    '''
+    while True:
+        reader.init()
+
+        # For now we omit the tag type
+        (stat, _) = reader.request(reader.REQIDL)
+        if stat == reader.OK:
+            (stat, uid) = reader.SelectTagSN()
+            if stat == reader.OK:
+                print(f"uid={uid_to_string(uid)}")
+
+        await asyncio.sleep_ms(poll_interval_ms)
+
+
+def main():
+    reader = MFRC522(spi_id=1, sck=10, miso=12, mosi=11, cs=13, rst=9, tocard_retries=1)
+
+    print("")
+    print("Please place card on reader")
+    print("")
+
+    asyncio.create_task(get_tag_uid(reader))
+    asyncio.create_task(latency_test())
+
+    asyncio.get_event_loop().run_forever()
+
+
+if __name__ == "__main__":
+    main()