SPI read_passive_target timeout

adafruit_pn532/spi.py

@@ -51,12 +51,7 @@
 def reverse_bit(num):
     """Turn an LSB byte to an MSB byte, and vice versa. Used for SPI as
     it is LSB for the PN532, but 99% of SPI implementations are MSB only!"""
-    result = 0
-    for _ in range(8):
-        result <<= 1
-        result += (num & 1)
-        num >>= 1
-    return result
+    return int('{:08b}'.format(num)[::-1], 2)
 
 class PN532_SPI(PN532):
     """Driver for the PN532 connected over SPI. Pass in a hardware or bitbang
@@ -81,14 +76,14 @@ def _wait_ready(self, timeout=1):
         status = bytearray([reverse_bit(_SPI_STATREAD), 0])
 
         timestamp = time.monotonic()
-        while (time.monotonic() - timestamp) < timeout:
-            with self._spi as spi:
-                time.sleep(0.02)   # required
+        with self._spi as spi:
+            while (time.monotonic() - timestamp) < timeout:
+                time.sleep(0.02)   # required (not needed when tested on rPi 3)
                 spi.write_readinto(status, status) #pylint: disable=no-member
-            if reverse_bit(status[1]) == 0x01:  # LSB data is read in MSB
-                return True      # Not busy anymore!
-            else:
-                time.sleep(0.01)  # pause a bit till we ask again
+                if reverse_bit(status[1]) == 0x01:  # LSB data is read in MSB
+                    return True      # Not busy anymore!
+                else: # (not needed when tested on rPi 3)
+                    time.sleep(0.01)  # pause a bit till we ask again
         # We timed out!
         return False
 
@@ -100,7 +95,7 @@ def _read_data(self, count):
         frame[0] = reverse_bit(_SPI_DATAREAD)
 
         with self._spi as spi:
-            time.sleep(0.02)   # required
+            time.sleep(0.02)   # required (not needed when tested on rPi 3)
             spi.write_readinto(frame, frame) #pylint: disable=no-member
         for i, val in enumerate(frame):
             frame[i] = reverse_bit(val) # turn LSB data to MSB
@@ -116,5 +111,5 @@ def _write_data(self, framebytes):
         if self.debug:
             print("Writing: ", [hex(i) for i in rev_frame])
         with self._spi as spi:
-            time.sleep(0.02)   # required
+            time.sleep(0.02)   # required (not needed when tested on rPi 3)
             spi.write(bytes(rev_frame)) #pylint: disable=no-member