Add named support for the PCAL9538

The PCAL9538 is identical to the PCAL9554 except for different default register values and i2c address.

Author: ilikecake

i2c_expanders/PCAL9538.py

@@ -0,0 +1,117 @@
+# SPDX-FileCopyrightText: 2023 Pat Satyshur
+# SPDX-FileCopyrightText: 2017 Tony DiCola for Adafruit Industries
+# SPDX-FileCopyrightText: 2019 Carter Nelson
+#
+# SPDX-License-Identifier: MIT
+
+# pylint: disable=too-many-public-methods, duplicate-code
+# Note: there is a bit of duplicated code between this and the other PCAL parts. This code is
+#       duplicated for these two expanders, but may not be if other expanders are added to this
+#       library. I therefore  want to keep is separate in these two classes. The line above
+#       disables the pylint check for this.
+
+"""
+`PCAL9538`
+====================================================
+
+CircuitPython module for the PCAL9538 I2C I/O extenders.
+The PCAL9554 is a 8 pin IO Expander. It is software compatible with the PCA9554, but has a
+bunch of added functions.
+
+Added features of these expanders include:
+
+* Built in pull up and pull down resistors.
+* Per pin selectable drive strength.
+* Maskable interrupt pins
+* Latching interrupt option
+* Per bank push-pull/open drain pin setup.
+
+Required library files (.py or their .mpy equivalent):
+
+* PCAL9538.py
+* PCAL9554.py
+* PCA9554.py
+* i2c_expander.py
+* digital_inout.py
+* helpers.py
+
+Compatible Devices
+
+* PCAL9554
+* PCAL9538
+
+These are devices I have specifically tested and know work. There appear to be a lot more devices
+with similar naming schemes that use the same register map. These should also be compatible, but
+make sure you check the i2c address and default register state.
+
+:Note: By default if an (non-latched) interrupt enabled pin changes state, but changes back before
+       the GPIO state register is read, the interrupt state will be cleared. Setting the interrupt
+       latch will cause the device to latch on a state change of the input pin. With latching
+       enabled, on a state change to the pin, the interrupt pin will be asserted and will not
+       deassert until the input register is read. The value read from the input register will be
+       the value that caused the interrupt, not nessecarially the current value of the pin. If the
+       pin changed state, but changed back before the input register was read, the changed state
+       will be what is returned in the register. The state change back to the original state will
+       not trigger another interrupt as long as it happens before the input register is read. If
+       the input register is read before the pin state changes back to the original value, both
+       state changes will cause an interrupt.
+
+Heavily based on the code written by Tony DiCola for the MCP230xx library.
+
+* Author(s): Pat Satyshur
+"""
+
+# TODO: Disable unused imports here. After I finish this code, turn that off and see if they
+# are still unused.
+# pylint: disable=unused-import
+from micropython import const
+import digitalio
+
+from i2c_expanders.PCAL9554 import PCAL9554
+from i2c_expanders.helpers import Capability, _get_bit, _enable_bit, _clear_bit
+
+
+__version__ = "0.0.0+auto.0"
+__repo__ = "https://github.com/ilikecake/CircuitPython_I2C_Expanders.git"
+
+# This is the default address for the PCA9538 with all addr pins grounded.
+_PCAL9538_DEFAULT_ADDRESS = const(0x70)
+
+
+class PCAL9538(PCAL9554):
+    """The class for the PCAL9538 expander. Instantiate one of these for each expander on the bus.
+    Make sure you get the address right.
+    """
+
+    def __init__(self, i2c, address=_PCAL9538_DEFAULT_ADDRESS, reset=True):
+        super().__init__(
+            i2c, address, False
+        )  # This initializes the PCA9554 compatible registers.
+        self._capability = (
+            _enable_bit(0x00, Capability.PULL_UP)
+            | _enable_bit(0x00, Capability.PULL_DOWN)
+            | _enable_bit(0x00, Capability.INVERT_POL)
+        )
+
+        if reset:
+            self.reset_to_defaults()
+
+    def reset_to_defaults(self):
+        """Reset all registers to their default state. This is also
+        done with a power cycle, but it can be called by software here.
+
+        :return:        Nothing.
+        """
+        # TODO: Should I make some sort of 'register' class to handle
+        #  memory addresses and default states?
+        # Input port and interrupt status registers are read only.
+        self.gpio = 0xFF
+        self.ipol = 0x00
+        self.iodir = 0xFF
+
+        self.out_drive = 0xFFFF
+        self.input_latch = 0x00
+        self.pupd_en = 0x00
+        self.pupd_sel = 0xFF
+        self.irq_mask = 0xFF
+        self.out_port_config = 0x00

i2c_expanders/PCAL9554.py

@@ -305,7 +305,7 @@ def reset_to_defaults(self):
 
         self.out_drive = 0xFFFF
         self.input_latch = 0x00
-        self.pupd_en = 0x00  # TODO: 0xFF for PCAL9554, 0x00 for PCAL9538
+        self.pupd_en = 0xFF
         self.pupd_sel = 0xFF
         self.irq_mask = 0xFF
         self.out_port_config = 0x00