Adding I2C Micropython code

README.md

@@ -67,7 +67,8 @@ Giuseppe Cassibba wrote up a [tutorial](https://peppe8o.com/using-i2c-lcd-displa
 | pyb_i2c_grove_rgb_lcd_test.py | Pyboard test using Grove I2C RGB LCD  |
 | pyb_i2c_lcd.py                | Pyboard PCF8574 I2C HAL               |
 | pyb_i2c_lcd_test.py           | Pyboard test using PCF8574 backpack   |
-
+| i2c_micropython_lcd.py        | Micropython I2C                       |
+| i2c_micropython_lcd_test.py   | Micropython I2C test using ESP32      |
 
 The files which end in **_test.py** are examples which show how the corresponding
 file is used.

lcd/i2c_micropython_lcd.py

@@ -0,0 +1,89 @@
+"""Implements a HD44780 character LCD connected via PCF8574 on I2C."""
+
+from lcd_api import LcdApi
+from machine import I2C
+import time
+
+# The PCF8574 has a jumper selectable address: 0x20 - 0x27
+DEFAULT_I2C_ADDR = 0x27
+
+# Defines shifts or masks for the various LCD line attached to the PCF8574
+
+MASK_RS = 0x01
+MASK_RW = 0x02
+MASK_E = 0x04
+SHIFT_BACKLIGHT = 3
+SHIFT_DATA = 4
+
+
+class I2cLcd(LcdApi):
+    """Implements a HD44780 character LCD connected via PCF8574 on I2C."""
+
+    def __init__(self, i2c, i2c_addr, num_lines, num_columns):
+        self.i2c_addr = i2c_addr
+        self.i2c = i2c
+        self.i2c.writeto(self.i2c_addr, bytearray([0]))
+        time.sleep(0.020)    # Allow LCD time to powerup
+        # Send reset 3 times
+        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
+        time.sleep(0.005)   # need to delay at least 4.1 msec
+        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
+        time.sleep(0.001)
+        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
+        time.sleep(0.001)
+        # Put LCD into 4 bit mode
+        self.hal_write_init_nibble(self.LCD_FUNCTION)
+        time.sleep(0.001)
+        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
+            time.sleep(0.005)
+
+    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]))

lcd/i2c_micropython_lcd_test.py

@@ -0,0 +1,65 @@
+"""Implements a HD44780 character LCD connected via PCF8574 on I2C."""
+
+from i2c_micropython_lcd import I2cLcd
+import machine
+import time
+
+# The PCF8574 has a jumper selectable address: 0x20 - 0x27
+DEFAULT_I2C_ADDR = 0x27
+
+def test_main():
+    """Test function for verifying basic functionality."""
+    sda = machine.Pin(18)
+    scl = machine.Pin(19)
+    i2c = machine.I2C(scl=scl, sda=sda, freq=100000)
+
+    lcd = I2cLcd(i2c, DEFAULT_I2C_ADDR, 4, 20)
+    lcd.blink_cursor_on()
+    lcd.putstr("It Works!\nSecond Line")
+    time.sleep(3)
+    lcd.clear()
+
+    # custom characters: battery icons - 5 wide, 8 tall
+    lcd.custom_char(0, bytearray([0x0E,0x1B,0x11,0x11,0x11,0x11,0x11,0x1F]))  # 0% Empty
+    lcd.custom_char(1, bytearray([0x0E,0x1B,0x11,0x11,0x11,0x11,0x1F,0x1F]))  # 16%
+    lcd.custom_char(2, bytearray([0x0E,0x1B,0x11,0x11,0x11,0x1F,0x1F,0x1F]))  # 33%
+    lcd.custom_char(3, bytearray([0x0E,0x1B,0x11,0x11,0x1F,0x1F,0x1F,0x1F]))  # 50%
+    lcd.custom_char(4, bytearray([0x0E,0x1B,0x11,0x1F,0x1F,0x1F,0x1F,0x1F]))  # 66%
+    lcd.custom_char(5, bytearray([0x0E,0x1B,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F]))  # 83%
+    lcd.custom_char(6, bytearray([0x0E,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F]))  # 100% Full
+    lcd.custom_char(7, bytearray([0x0E,0x1F,0x1B,0x1B,0x1B,0x1F,0x1B,0x1F]))  # ! Error
+    for i in range(8):
+        lcd.putchar(chr(i))
+    time.sleep(3)
+    lcd.clear()
+    lcd.blink_cursor_off()
+
+    count = 0
+    while True:
+        lcd.move_to(0, 0)
+        lcd.putstr("Time: " + str(time.time()))
+        time.sleep(1)
+        count += 1
+        if count % 10 == 3:
+            print("Turning backlight off")
+            lcd.backlight_off()
+        if count % 10 == 4:
+            print("Turning backlight on")
+            lcd.backlight_on()
+        if count % 10 == 5:
+            print("Turning display off")
+            lcd.display_off()
+        if count % 10 == 6:
+            print("Turning display on")
+            lcd.display_on()
+        if count % 10 == 7:
+            print("Turning display & backlight off")
+            lcd.backlight_off()
+            lcd.display_off()
+        if count % 10 == 8:
+            print("Turning display & backlight on")
+            lcd.backlight_on()
+            lcd.display_on()
+
+if __name__ == "__main__":
+    test_main()