Create I2C_LCD.py

Added LCD class for Micropython
Danielerikrust · Feb 21, 2023 · 409ef9f · 409ef9f
1 parent c014cf1
commit 409ef9f
Showing 1 changed file with 79 additions and 0 deletions.
diff --git a/I2C_LCD.py b/I2C_LCD.py
@@ -0,0 +1,79 @@
+from LCD_API import LcdApi
+from machine import I2C
+from time import sleep_ms
+
+# Defines shifts or masks for the various LCD line attached to the PCF8574
+# wire black to GND
+# wire white to VSYS
+# wire grey to GPIO 2
+# wire purple to GPIO 3
+
+# 8574AT chip = 0x3F address
+
+MASK_RS = 0x01
+MASK_RW = 0x02
+MASK_E = 0x04
+SHIFT_BACKLIGHT = 3
+SHIFT_DATA = 4
+
+
+class I2CLcd(LcdApi):
+    def __init__(self, i2c, i2c_addr, num_lines, num_columns):
+        self.i2c = i2c
+        self.i2c_addr = i2c_addr
+        self.i2c.writeto(self.i2c_addr, bytearray([0]))
+        sleep_ms(20)   # Allow LCD time to powerup
+        # Send reset 3 times
+        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
+        sleep_ms(5)    # need to delay at least 4.1 msec
+        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
+        sleep_ms(1)
+        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
+        sleep_ms(1)
+        # Put LCD into 4 bit mode
+        self.hal_write_init_nibble(self.LCD_FUNCTION)
+        sleep_ms(1)
+        LcdApi.__init__(self, num_lines, num_columns)
+        cmd = self.LCD_FUNCTION
+        if num_lines > 1:
+            cmd |= self.LCD_FUNCTION_2LINES
+        self.hal_write_command(cmd)
+
+    def hal_write_init_nibble(self, nibble):
+        """Writes an initialization nibble to the LCD.
+        This particular function is only used during initialization.
+        """
+        byte = ((nibble >> 4) & 0x0f) << SHIFT_DATA
+        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte]))
+
+    def hal_backlight_on(self):
+        """Allows the hal layer to turn the backlight on."""
+        self.i2c.writeto(self.i2c_addr, bytearray([1 << SHIFT_BACKLIGHT]))
+
+    def hal_backlight_off(self):
+        """Allows the hal layer to turn the backlight off."""
+        self.i2c.writeto(self.i2c_addr, bytearray([0]))
+
+    def hal_write_command(self, cmd):
+        """Writes a command to the LCD.
+        Data is latched on the falling edge of E.
+        """
+        byte = ((self.backlight << SHIFT_BACKLIGHT) | (((cmd >> 4) & 0x0f) << SHIFT_DATA))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte]))
+        byte = ((self.backlight << SHIFT_BACKLIGHT) | ((cmd & 0x0f) << SHIFT_DATA))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte]))
+        if cmd <= 3:
+            # The home and clear commands require a worst case delay of 4.1 msec
+            sleep_ms(5)
+
+    def hal_write_data(self, data):
+        """Write data to the LCD."""
+        byte = (MASK_RS | (self.backlight << SHIFT_BACKLIGHT) | (((data >> 4) & 0x0f) << SHIFT_DATA))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte]))
+        byte = (MASK_RS | (self.backlight << SHIFT_BACKLIGHT) | ((data & 0x0f) << SHIFT_DATA))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte]))