adafruit_pio_uart.receive() should return None on no bytes received (timeout), to match busio.UART

Author: todbot

adafruit_pio_uart.py

@@ -184,6 +184,8 @@ def read(self, n):
         else:
             buf = bytearray(n)
         n = self.readinto(buf)
+        if n == 0:
+            return None
         if n < len(buf):
             return buf[:n]
         return buf