Character_LCD_I2C: add support for PCF8574 I2C expander backpack

README.rst

@@ -55,6 +55,7 @@ This driver depends on:
 * `Adafruit CircuitPython <https://github.com/adafruit/circuitpython>`_
 * `Adafruit CircuitPython BusDevice <https://github.com/adafruit/Adafruit_CircuitPython_BusDevice>`_
 * `Adafruit CircuitPython MCP230xx <https://github.com/adafruit/Adafruit_CircuitPython_MCP230xx>`_
+* `Adafruit CircuitPython PCF8574 <https://github.com/adafruit/Adafruit_CircuitPython_PCF8574>`_
 * `Adafruit CircuitPython 74HC595 <https://github.com/adafruit/Adafruit_CircuitPython_74HC595>`_
 
 I2C & SPI displays also depend on:

adafruit_character_lcd/character_lcd_i2c.py

@@ -36,12 +36,23 @@
     pass
 
 from adafruit_mcp230xx.mcp23008 import MCP23008
+from adafruit_pcf8574 import PCF8574
 from adafruit_character_lcd.character_lcd import Character_LCD_Mono
 
 __version__ = "0.0.0+auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_CharLCD.git"
 
 
+class I2C_Expander:
+    # pylint: disable=too-few-public-methods
+    """
+    I2C Expander ICs
+    """
+
+    MCP23008 = "MCP23008"
+    PCF8574 = "PCF8574"
+
+
 class Character_LCD_I2C(Character_LCD_Mono):
     # pylint: disable=too-few-public-methods
     """Character LCD connected to I2C/SPI backpack using its I2C connection.
@@ -67,28 +78,50 @@ def __init__(
         lines: int,
         address: Optional[int] = None,
         backlight_inverted: bool = False,
+        expander: I2C_Expander = I2C_Expander.MCP23008,
     ) -> None:
         """Initialize character LCD connected to backpack using I2C connection
         on the specified I2C bus with the specified number of columns and
         lines on the display. Optionally specify if backlight is inverted.
         """
 
-        if address:
-            self.mcp = MCP23008(i2c, address=address)
-        else:
-            self.mcp = MCP23008(i2c)
-        super().__init__(
-            self.mcp.get_pin(1),  # reset
-            self.mcp.get_pin(2),  # enable
-            self.mcp.get_pin(3),  # data line 4
-            self.mcp.get_pin(4),  # data line 5
-            self.mcp.get_pin(5),  # data line 6
-            self.mcp.get_pin(6),  # data line 7
-            columns,
-            lines,
-            backlight_pin=self.mcp.get_pin(7),
-            backlight_inverted=backlight_inverted,
-        )
+        if expander == I2C_Expander.MCP23008:
+            if address:
+                self.expander = MCP23008(i2c, address=address)
+            else:
+                self.expander = MCP23008(i2c)
+
+            super().__init__(
+                self.expander.get_pin(1),  # reset
+                self.expander.get_pin(2),  # enable
+                self.expander.get_pin(3),  # data line 4
+                self.expander.get_pin(4),  # data line 5
+                self.expander.get_pin(5),  # data line 6
+                self.expander.get_pin(6),  # data line 7
+                columns,
+                lines,
+                backlight_pin=self.expander.get_pin(7),
+                backlight_inverted=backlight_inverted,
+            )
+
+        elif expander == I2C_Expander.PCF8574:
+            if address:
+                self.expander = PCF8574(i2c, address=address)
+            else:
+                self.expander = PCF8574(i2c)
+
+            super().__init__(
+                self.expander.get_pin(0),  # reset
+                self.expander.get_pin(2),  # enable
+                self.expander.get_pin(4),  # data line 4
+                self.expander.get_pin(5),  # data line 5
+                self.expander.get_pin(6),  # data line 6
+                self.expander.get_pin(7),  # data line 7
+                columns,
+                lines,
+                backlight_pin=self.expander.get_pin(3),
+                backlight_inverted=backlight_inverted,
+            )
 
     def _write8(self, value: int, char_mode: bool = False) -> None:
         # Sends 8b ``value`` in ``char_mode``.
@@ -98,27 +131,47 @@ def _write8(self, value: int, char_mode: bool = False) -> None:
         #  one ms delay to prevent writing too quickly.
         time.sleep(0.001)
 
-        # bits are, MSB (7) to LSB (0)
-        # backlight:   bit 7
-        # data line 7: bit 6
-        # data line 6: bit 5
-        # data line 5: bit 4
-        # data line 4: bit 3
-        # enable:      bit 2
-        # reset:       bit 1
-        # (unused):    bit 0
-
-        reset_bit = int(char_mode) << 1
-        backlight_bit = int(self.backlight ^ self.backlight_inverted) << 7
-
-        # Write char_mode and upper 4 bits of data, shifted to the correct position.
-        self.mcp.gpio = reset_bit | backlight_bit | ((value & 0xF0) >> 1)
-
-        #  do command
-        self._pulse_enable()
-
-        # Write char_mode and lower 4 bits of data, shifted to the correct position.
-        self.mcp.gpio = reset_bit | backlight_bit | ((value & 0x0F) << 3)
-
-        # do command
+        if isinstance(self.expander, MCP23008):
+            # bits are, MSB (7) to LSB (0)
+            # backlight:   bit 7
+            # data line 7: bit 6
+            # data line 6: bit 5
+            # data line 5: bit 4
+            # data line 4: bit 3
+            # enable:      bit 2
+            # reset:       bit 1
+            # (unused):    bit 0
+
+            reset_bit = int(char_mode) << 1
+            backlight_bit = int(self.backlight ^ self.backlight_inverted) << 7
+
+            # Write char_mode and upper 4 bits of data, shifted to the correct position.
+            self.__write_command(reset_bit | backlight_bit | ((value & 0xF0) >> 1))
+            self.__write_command(reset_bit | backlight_bit | ((value & 0x0F) << 3))
+
+        elif isinstance(self.expander, PCF8574):
+            # bits are, MSB (7) to LSB (0)
+            # data line 7: bit 7
+            # data line 6: bit 6
+            # data line 5: bit 5
+            # data line 4: bit 4
+            # backlight:   bit 3
+            # enable:      bit 2
+            # write/read:  bit 1
+            # reset:       bit 0
+            reset_bit = int(char_mode)
+            backlight_bit = int(self.backlight ^ self.backlight_inverted) << 3
+
+            # Write char_mode and upper 4 bits of data, shifted to the correct position.
+            self.__write_command(reset_bit | backlight_bit | (value & 0xF0))
+            self.__write_command(reset_bit | backlight_bit | (value << 4))
+
+    def __write_command(self, value: int) -> None:
+        # Write command bits to expander.
+        if isinstance(self.expander, MCP23008):
+            self.expander.gpio = value
+        elif isinstance(self.expander, PCF8574):
+            self.expander.write_gpio(value)
+
+        # execute command
         self._pulse_enable()

requirements.txt

@@ -4,6 +4,7 @@
 
 Adafruit-Blinka
 adafruit-circuitpython-mcp230xx
+adafruit-circuitpython-pcf8574
 adafruit-circuitpython-busdevice
 adafruit-circuitpython-74hc595
 adafruit-circuitpython-typing~=1.5