diff --git a/adafruit_pn532/adafruit_pn532.py b/adafruit_pn532/adafruit_pn532.py
index 7379a5a..d6100e7 100644
--- a/adafruit_pn532/adafruit_pn532.py
+++ b/adafruit_pn532/adafruit_pn532.py
@@ -343,12 +343,12 @@ class PN532:
         hard power down is performed, if not, a soft power down is performed
         instead. Returns True if the PN532 was powered down successfully or
         False if not."""
-        if self._reset_pin: # Hard Power Down if the reset pin is connected
+        if self._reset_pin:  # Hard Power Down if the reset pin is connected
             self._reset_pin.value = False
             self.low_power = True
         else:
             # Soft Power Down otherwise. Enable wakeup on I2C, SPI, UART
-            response = self.call_function(_COMMAND_POWERDOWN, params=[0xb0, 0x00])
+            response = self.call_function(_COMMAND_POWERDOWN, params=[0xB0, 0x00])
             self.low_power = response[0] == 0x00
         time.sleep(0.005)
         return self.low_power
diff --git a/adafruit_pn532/i2c.py b/adafruit_pn532/i2c.py
index 9c3ee09..463b988 100644
--- a/adafruit_pn532/i2c.py
+++ b/adafruit_pn532/i2c.py
@@ -71,7 +71,7 @@ class PN532_I2C(PN532):
             self._req.value = True
             time.sleep(0.01)
         self.low_power = False
-        self.SAM_configuration() # Put the PN532 back in normal mode
+        self.SAM_configuration()  # Put the PN532 back in normal mode
 
     def _wait_ready(self, timeout=1):
         """Poll PN532 if status byte is ready, up to `timeout` seconds"""
diff --git a/adafruit_pn532/spi.py b/adafruit_pn532/spi.py
index 943dad5..627584b 100644
--- a/adafruit_pn532/spi.py
+++ b/adafruit_pn532/spi.py
@@ -79,7 +79,7 @@ class PN532_SPI(PN532):
             spi.write(bytearray([0x00]))  # pylint: disable=no-member
             time.sleep(0.01)
         self.low_power = False
-        self.SAM_configuration() # Put the PN532 back in normal mode
+        self.SAM_configuration()  # Put the PN532 back in normal mode
 
     def _wait_ready(self, timeout=1):
         """Poll PN532 if status byte is ready, up to `timeout` seconds"""
diff --git a/adafruit_pn532/uart.py b/adafruit_pn532/uart.py
index e52d22b..915bc5b 100644
--- a/adafruit_pn532/uart.py
+++ b/adafruit_pn532/uart.py
@@ -61,7 +61,7 @@ class PN532_UART(PN532):
         self.low_power = False
         self._uart.write(
             b"\x55\x55\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
-        ) # wake up!
+        )  # wake up!
         self.SAM_configuration()
 
     def _wait_ready(self, timeout=1):
@@ -69,7 +69,7 @@ class PN532_UART(PN532):
         timestamp = time.monotonic()
         while (time.monotonic() - timestamp) < timeout:
             if self._uart.in_waiting > 0:
-                return True # No Longer Busy
+                return True  # No Longer Busy
             time.sleep(0.01)  # lets ask again soon!
         # Timed out!
         return False