No idea what I'm committing here, but it goes on github

aabiot/wiegand.py

@@ -0,0 +1,73 @@
+"""
+weigand.py - read card IDs from a wiegand card reader
+
+(C) 2017 Paul Jimenez - released under LGPLv3+
+"""
+
+from machine import Pin, Timer
+import utime
+
+CARD_MASK = 0b11111111111111110 # 16 ones
+FACILITY_MASK = 0b1111111100000000000000000 # 8 ones
+
+# Max pulse interval: 2ms
+# pulse width: 50us
+
+class Wiegand:
+    def __init__(self, pin0, pin1, callback):
+        """
+        pin0 - the GPIO that goes high when a zero is sent by the reader
+        pin1 - the GPIO that goes high when a one is sent by the reader
+        callback - the function called (with two args: card ID and cardcount)
+                   when a card is detected.  Note that micropython interrupt
+                   implementation limitations apply to the callback!
+        """
+        self.pin0 = Pin(pin0, Pin.IN)
+        self.pin1 = Pin(pin1, Pin.IN)
+        self.callback = callback
+        self.last_card = None
+        self.next_card = 0
+        self._bits = 0
+        self.pin0.irq(trigger=Pin.IRQ_FALLING, handler=self._on_pin0)
+        self.pin1.irq(trigger=Pin.IRQ_FALLING, handler=self._on_pin1)
+        self.last_bit_read = None
+        self.timer = Timer(-1)
+        self.timer.init(period=50, mode=Timer.PERIODIC, callback=self._cardcheck)
+        self.cards_read = 0
+
+    def _on_pin0(self, newstate): self._on_pin(0, newstate)
+    def _on_pin1(self, newstate): self._on_pin(1, newstate)
+
+    def _on_pin(self, is_one, newstate):
+        now = utime.ticks_ms()
+        if self.last_bit_read is not None and now - self.last_bit_read < 2:
+            # too fast
+            return
+
+        self.last_bit_read = now
+        self.next_card <<= 1
+        if is_one: self.next_card |= 1
+        self._bits += 1
+
+    def get_card(self):
+        if self.last_card is None:
+            return None
+        return ( self.last_card & CARD_MASK ) >> 1
+        
+    def get_facility_code(self):
+        if self.last_card is None:
+            return None
+        # Specific to standard 26bit wiegand
+        return ( self.last_card & FACILITY_MASK ) >> 17
+
+    def _cardcheck(self, t):
+        if self.last_bit_read is None: return
+        now = utime.ticks_ms()
+        if now - self.last_bit_read > 50:
+            # too slow - new start!
+            self.last_bit_read = None
+            self.last_card = self.next_card
+            self.next_card = 0
+            self._bits = 0
+            self.cards_read += 1
+            self.callback(self.get_card(), self.get_facility_code(), self.cards_read)