Merge pull request #80 from dhalbert/faster-I2C

Speed up I2C by not setting the MCP23008 bits one at a time.

Author: dhalbert

.pre-commit-config.yaml

@@ -18,7 +18,7 @@ repos:
       - id: end-of-file-fixer
       - id: trailing-whitespace
   - repo: https://github.com/pycqa/pylint
-    rev: v2.17.4
+    rev: v3.3.1
     hooks:
       - id: pylint
         name: pylint (library code)

.pylintrc

@@ -361,7 +361,7 @@ valid-metaclass-classmethod-first-arg=mcs
 [DESIGN]
 
 # Maximum number of arguments for function / method
-max-args=5
+max-args=13
 
 # Maximum number of attributes for a class (see R0902).
 # max-attributes=7

adafruit_character_lcd/character_lcd.py

@@ -103,7 +103,7 @@ def _map(
     return ret
 
 
-# pylint: disable-msg=too-many-instance-attributes
+# pylint: disable=too-many-instance-attributes
 class Character_LCD:
     """Base class for character LCD.
 
@@ -121,7 +121,7 @@ class Character_LCD:
     LEFT_TO_RIGHT = const(0)
     RIGHT_TO_LEFT = const(1)
 
-    # pylint: disable-msg=too-many-arguments
+    # pylint: disable=too-many-positional-arguments
     def __init__(
         self,
         reset_dio: digitalio.DigitalInOut,
@@ -163,9 +163,10 @@ def __init__(
         # Set entry mode
         self._write8(_LCD_ENTRYMODESET | self.displaymode)
         self.clear()
-        self._message = None
-        self._enable = None
-        self._direction = None
+
+        self._message = ""
+        self._backlight_on = False
+        self._direction = self.LEFT_TO_RIGHT
         # track row and column used in cursor_position
         # initialize to 0,0
         self.row = 0
@@ -535,7 +536,7 @@ def _pulse_enable(self) -> None:
 # pylint: enable-msg=too-many-instance-attributes
 
 
-# pylint: disable-msg=too-many-instance-attributes
+# pylint: disable=too-many-instance-attributes
 class Character_LCD_Mono(Character_LCD):
     """Interfaces with monochromatic character LCDs.
 
@@ -554,7 +555,7 @@ class Character_LCD_Mono(Character_LCD):
 
     """
 
-    # pylint: disable-msg=too-many-arguments
+    # pylint: disable=too-many-positional-arguments
     def __init__(
         self,
         reset_dio: digitalio.DigitalInOut,
@@ -607,15 +608,12 @@ def backlight(self) -> Optional[bool]:
             time.sleep(5)
 
         """
-        return self._enable
+        return self._backlight_on
 
     @backlight.setter
-    def backlight(self, enable: bool) -> None:
-        self._enable = enable
-        if enable:
-            self.backlight_pin.value = not self.backlight_inverted
-        else:
-            self.backlight_pin.value = self.backlight_inverted
+    def backlight(self, enable):
+        self._backlight_on = enable
+        self.backlight_pin.value = enable ^ self.backlight_inverted
 
 
 class Character_LCD_RGB(Character_LCD):
@@ -637,7 +635,7 @@ class Character_LCD_RGB(Character_LCD):
 
     """
 
-    # pylint: disable-msg=too-many-arguments
+    # pylint: disable=too-many-positional-arguments
     def __init__(
         self,
         reset_dio: digitalio.DigitalInOut,

adafruit_character_lcd/character_lcd_i2c.py

@@ -27,6 +27,8 @@
   https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
 
 """
+import time
+
 try:
     from typing import Optional
     import busio
@@ -41,7 +43,7 @@
 
 
 class Character_LCD_I2C(Character_LCD_Mono):
-    # pylint: disable=too-few-public-methods, too-many-arguments
+    # pylint: disable=too-few-public-methods
     """Character LCD connected to I2C/SPI backpack using its I2C connection.
     This is a subclass of `Character_LCD_Mono` and implements all the same
     functions and functionality.
@@ -57,6 +59,7 @@ class Character_LCD_I2C(Character_LCD_Mono):
         lcd = Character_LCD_I2C(i2c, 16, 2)
     """
 
+    # pylint: disable=too-many-positional-arguments
     def __init__(
         self,
         i2c: busio.I2C,
@@ -71,18 +74,51 @@ def __init__(
         """
 
         if address:
-            mcp = MCP23008(i2c, address=address)
+            self.mcp = MCP23008(i2c, address=address)
         else:
-            mcp = MCP23008(i2c)
+            self.mcp = MCP23008(i2c)
         super().__init__(
-            mcp.get_pin(1),
-            mcp.get_pin(2),
-            mcp.get_pin(3),
-            mcp.get_pin(4),
-            mcp.get_pin(5),
-            mcp.get_pin(6),
+            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=mcp.get_pin(7),
+            backlight_pin=self.mcp.get_pin(7),
             backlight_inverted=backlight_inverted,
         )
+
+    def _write8(self, value: int, char_mode: bool = False) -> None:
+        # Sends 8b ``value`` in ``char_mode``.
+        # :param value: bytes
+        # :param char_mode: character/data mode selector. False (default) for
+        # data only, True for character bits.
+        #  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
+        self._pulse_enable()

adafruit_character_lcd/character_lcd_spi.py

@@ -59,7 +59,8 @@ class Character_LCD_SPI(Character_LCD_Mono):  # pylint: disable=too-few-public-m
         lcd = character_lcd.Character_LCD_SPI(spi, latch, 16, 2)
     """
 
-    def __init__(  # pylint: disable=too-many-arguments
+    # pylint: disable=too-many-positional-arguments
+    def __init__(
         self,
         spi: busio.SPI,
         latch: digitalio.DigitalInOut,