do a hardware reset before I2C, tested with raspi

Author: ladyada

adafruit_pn532.py

@@ -176,6 +176,14 @@
 # pylint: enable=bad-whitespace
 
 
+def _reset(pin):
+    pin.direction = Direction.OUTPUT
+    pin.value = True
+    time.sleep(0.1)
+    pin.value = False
+    time.sleep(0.5)
+    pin.value = True
+    time.sleep(0.1)
 
 def reverse_bit(num):
     """Turn an LSB byte to an MSB byte, and vice versa. Used for SPI as
@@ -201,13 +209,10 @@ def __init__(self, *, debug=False, reset=None):
         """
         self.debug = debug
         if reset:
-            reset.direction = Direction.OUTPUT
-            reset.value = True
-            time.sleep(0.1)
-            reset.value = False
-            time.sleep(0.5)
-            reset.value = True
-            time.sleep(0.1)
+            if debug:
+                print("Resetting")
+            _reset(reset)
+
         try:
             self._wakeup()
             self.get_firmware_version() # first time often fails, try 2ce
@@ -311,7 +316,11 @@ def call_function(self, command, response_length=0, params=[], timeout=1): # pyl
         for i, val in enumerate(params):
             data[2+i] = val
         # Send frame and wait for response.
-        self._write_frame(data)
+        try:
+            self._write_frame(data)
+        except OSError:
+            self._wakeup()
+            return None
         if not self._wait_ready(timeout):
             return None
         # Verify ACK response and wait to be ready for function response.
@@ -470,27 +479,41 @@ def _write_data(self, framebytes):
 
 class PN532_I2C(PN532):
     """Driver for the PN532 connected over I2C."""
-    def __init__(self, i2c, *, irq=None, reset=None, debug=False):
+    def __init__(self, i2c, *, irq=None, reset=None, req=None, debug=False):
         """Create an instance of the PN532 class using I2C. Note that PN532
         uses clock stretching. Optional IRQ pin (not used),
         reset pin and debugging output.
         """
         self.debug = debug
         self._irq = irq
+        self._req = req
+        if reset:
+            _reset(reset)
         self._i2c = i2c_device.I2CDevice(i2c, _I2C_ADDRESS)
         super().__init__(debug=debug, reset=reset)
 
     def _wakeup(self): # pylint: disable=no-self-use
         """Send any special commands/data to wake up PN532"""
+        if self._req:
+            self._req.direction = Direction.OUTPUT
+            self._req.value = True
+            time.sleep(0.1)
+            self._req.value = False
+            time.sleep(0.1)
+            self._req.value = True
         time.sleep(0.5)
 
     def _wait_ready(self, timeout=1):
         """Poll PN532 if status byte is ready, up to `timeout` seconds"""
         status = bytearray(1)
         timestamp = time.monotonic()
         while (time.monotonic() - timestamp) < timeout:
-            with self._i2c:
-                self._i2c.readinto(status)
+            try:
+                with self._i2c:
+                    self._i2c.readinto(status)
+            except OSError:
+                self._wakeup()
+                continue
             if status == b'\x01':
                 return True  # No longer busy
             else:

examples/pn532_simpletest.py

@@ -10,20 +10,28 @@
 from digitalio import DigitalInOut
 from Adafruit_Circuitpython_PN532 import adafruit_pn532
 
-reset_pin = DigitalInOut(board.D6)
-
 # I2C connection:
 i2c = busio.I2C(board.SCL, board.SDA)
-pn532 = adafruit_pn532.PN532_I2C(i2c, debug=False, reset=reset_pin)
+
+# Non-hardware 
+#pn532 = adafruit_pn532.PN532_I2C(i2c, debug=False)
+
+# With I2C, we recommend connecting RSTPD_N (reset) to a digital pin for manual
+# harware reset
+reset_pin = DigitalInOut(board.D6)
+# On Raspberry Pi, you must also connect a pin to P32 "H_Request" for hardware
+# wakeup! this means we don't need to do the I2C clock-stretch thing
+req_pin = DigitalInOut(board.D12)
+pn532 = adafruit_pn532.PN532_I2C(i2c, debug=False, reset=reset_pin, req=req_pin)
 
 # SPI connection:
 #spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
 #cs_pin = DigitalInOut(board.D5)
-#pn532 = adafruit_pn532.PN532_SPI(spi, cs_pin, debug=False, reset=reset_pin)
+#pn532 = adafruit_pn532.PN532_SPI(spi, cs_pin, debug=False)
 
 # UART connection
 #uart = busio.UART(board.TX, board.RX, baudrate=115200, timeout=100)
-#pn532 = adafruit_pn532.PN532_UART(uart, debug=False, reset=reset_pin)
+#pn532 = adafruit_pn532.PN532_UART(uart, debug=False)
 
 ic, ver, rev, support = pn532.get_firmware_version()
 print('Found PN532 with firmware version: {0}.{1}'.format(ver, rev))
@@ -34,7 +42,7 @@
 print('Waiting for RFID/NFC card...')
 while True:
     # Check if a card is available to read
-    uid = pn532.read_passive_target(timeout=0.25)
+    uid = pn532.read_passive_target(timeout=0.5)
     print('.', end="", flush=True)
     # Try again if no card is available.
     if uid is None: