Add support for the old, deprecated MCP23016 expander, too.

The main difference with the '17 is that it lacks advanced interrupt
control features, and pull-up configuration.

This includes changes to DigitalInOut to raise ValueError when trying to
set pull-up configuration as well as pull-down, on the MCP23016 only.

Author: Flameeyes

adafruit_mcp230xx/digital_inout.py

@@ -32,9 +32,13 @@ def _clear_bit(val, bit):
 
 class DigitalInOut:
     """Digital input/output of the MCP230xx.  The interface is exactly the
-    same as the digitalio.DigitalInOut class (however the MCP230xx does not
-    support pull-down resistors and an exception will be thrown
-    attempting to set one).
+    same as the digitalio.DigitalInOut class, however:
+
+      * MCP230xx family does not support pull-down resistors;
+      * MCP23016 does not support pull-up resistors.
+
+    Exceptions will be thrown when attempting to set unsupported pull
+    configurations.
     """
 
     def __init__(self, pin_number, mcp230xx):
@@ -105,17 +109,25 @@ def pull(self):
         value of digitalio.Pull.UP will enable a pull-up resistor, and None will
         disable it.  Pull-down resistors are NOT supported!
         """
-        if _get_bit(self._mcp.gppu, self._pin):
-            return digitalio.Pull.UP
+        try:
+            if _get_bit(self._mcp.gppu, self._pin):
+                return digitalio.Pull.UP
+        except AttributeError:
+            # MCP23016 doesn't have a `gppu` register.
+            raise ValueError("Pull-up/pull-down resistors not supported.")
         return None
 
     @pull.setter
     def pull(self, val):
-        if val is None:
-            self._mcp.gppu = _clear_bit(self._mcp.gppu, self._pin)
-        elif val == digitalio.Pull.UP:
-            self._mcp.gppu = _enable_bit(self._mcp.gppu, self._pin)
-        elif val == digitalio.Pull.DOWN:
-            raise ValueError("Pull-down resistors are not supported!")
-        else:
-            raise ValueError("Expected UP, DOWN, or None for pull state!")
+        try:
+            if val is None:
+                self._mcp.gppu = _clear_bit(self._mcp.gppu, self._pin)
+            elif val == digitalio.Pull.UP:
+                self._mcp.gppu = _enable_bit(self._mcp.gppu, self._pin)
+            elif val == digitalio.Pull.DOWN:
+                raise ValueError("Pull-down resistors are not supported!")
+            else:
+                raise ValueError("Expected UP, DOWN, or None for pull state!")
+        except AttributeError:
+            # MCP23016 doesn't have a `gppu` register.
+            raise ValueError("Pull-up/pull-down resistors not supported.")

adafruit_mcp230xx/mcp23016.py

@@ -0,0 +1,131 @@
+# SPDX-FileCopyrightText: 2017 Tony DiCola for Adafruit Industries
+# SPDX-FileCopyrightText: 2019 Carter Nelson
+# SPDX-FileCopyrightText: 2020 Facebook Inc.
+#
+# SPDX-License-Identifier: MIT
+
+"""
+`mcp23016`
+====================================================
+
+CircuitPython module for the MCP23016 I2C I/O extenders.
+
+* Author(s): Diego Elio Pettenò (based on MCP23017.py)
+"""
+
+from micropython import const
+from .mcp230xx import MCP230XX
+from .digital_inout import DigitalInOut
+
+__version__ = "0.0.0-auto.0"
+__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_MCP230xx.git"
+
+# pylint: disable=bad-whitespace
+_MCP23016_ADDRESS = const(0x20)
+_MCP23016_GPIO0 = const(0x00)
+_MCP23016_GPIO1 = const(0x01)
+_MCP23016_IPOL0 = const(0x04)
+_MCP23016_IPOL1 = const(0x05)
+_MCP23016_IODIR0 = const(0x06)
+_MCP23016_IODIR1 = const(0x07)
+_MCP23016_INTCAP0 = const(0x08)
+_MCP23016_INTCAP1 = const(0x09)
+_MCP23016_IOCON0 = const(0x0A)
+_MCP23016_IOCON1 = const(0x0B)
+
+
+class MCP23016(MCP230XX):
+    """Supports MCP23016 instance on specified I2C bus and optionally
+    at the specified I2C address.
+    """
+
+    def __init__(self, i2c, address=_MCP23016_ADDRESS):
+        super().__init__(i2c, address)
+
+        # Reset to all inputs and no inverted polarity.
+        self.iodir = 0xFFFF
+        self._write_u16le(_MCP23016_IPOL0, 0x0000)
+
+    @property
+    def gpio(self):
+        """The raw GPIO output register.  Each bit represents the
+        output value of the associated pin (0 = low, 1 = high), assuming that
+        pin has been configured as an output previously.
+        """
+        return self._read_u16le(_MCP23016_GPIO0)
+
+    @gpio.setter
+    def gpio(self, val):
+        self._write_u16le(_MCP23016_GPIO0, val)
+
+    @property
+    def gpio0(self):
+        """The raw GPIO 0 output register.  Each bit represents the
+        output value of the associated pin (0 = low, 1 = high), assuming that
+        pin has been configured as an output previously.
+        """
+        return self._read_u8(_MCP23016_GPIO0)
+
+    @gpio0.setter
+    def gpio0(self, val):
+        self._write_u8(_MCP23016_GPIO0, val)
+
+    @property
+    def gpio1(self):
+        """The raw GPIO 1 output register.  Each bit represents the
+        output value of the associated pin (0 = low, 1 = high), assuming that
+        pin has been configured as an output previously.
+        """
+        return self._read_u8(_MCP23016_GPIO1)
+
+    @gpio1.setter
+    def gpio1(self, val):
+        self._write_u8(_MCP23016_GPIO1, val)
+
+    @property
+    def iodir(self):
+        """The raw IODIR direction register.  Each bit represents
+        direction of a pin, either 1 for an input or 0 for an output mode.
+        """
+        return self._read_u16le(_MCP23016_IODIR0)
+
+    @iodir.setter
+    def iodir(self, val):
+        self._write_u16le(_MCP23016_IODIR0, val)
+
+    @property
+    def iodir0(self):
+        """The raw IODIR0 direction register.  Each bit represents
+        direction of a pin, either 1 for an input or 0 for an output mode.
+        """
+        return self._read_u8(_MCP23016_IODIR0)
+
+    @iodir0.setter
+    def iodir0(self, val):
+        self._write_u8(_MCP23016_IODIR0, val)
+
+    @property
+    def iodir1(self):
+        """The raw IODIR0 direction register.  Each bit represents
+        direction of a pin, either 1 for an input or 0 for an output mode.
+        """
+        return self._read_u8(_MCP23016_IODIR1)
+
+    @iodir1.setter
+    def iodir1(self, val):
+        self._write_u8(_MCP23016_IODIR1, val)
+
+    def get_pin(self, pin):
+        """Convenience function to create an instance of the DigitalInOut class
+        pointing at the specified pin of this MCP23017 device.
+        """
+        assert 0 <= pin <= 15
+        return DigitalInOut(pin, self)
+
+    def clear_int0(self):
+        """Clears port 0 interrupts."""
+        self._read_u8(_MCP23016_INTCAP0)
+
+    def clear_int1(self):
+        """Clears port 1 interrupts."""
+        self._read_u8(_MCP23016_INTCAP1)