"""Program 3-3: Blink message "Hello" using 4-bit data mode and write only"""

import time
from machine import Pin

# Enable pin
LCD_E  = Pin(26, Pin.OUT)
LCD_E.off()
# Register Select pin, 1 - data, 0 - command
LCD_RS = Pin(27, Pin.OUT)

# Four bit data pins
dataPins = (18, 19, 20, 21)

# Empty list for data pin objects
LCD_D = []
# Construct the list of data pin objects
for p in dataPins:
    LCD_D.append(Pin(p, Pin.OUT))

def lcd_set_data_bits(data):
    """Set the eight data pins according to parameter data"""
    for i in range(0, 4):
        # For each pin set the value according to the corresponding bit
        LCD_D[i].value(data & (1 << (i + 4)))

def lcd_write_nibble(data):
    """Write the upper nibble of the data byte"""
    lcd_set_data_bits(data)
    LCD_E.on()
    time.sleep_us(1)
    LCD_E.off()

def lcd_write_byte(data):
    """Write a byte of data to the LCD controller"""
    lcd_write_nibble(data)       # write upper nibble
    lcd_write_nibble(data << 4)  # write lower nibble

def lcd_command(data):
    """write a command to the LCD controller"""
    # RS pin = 0, write to command register
    LCD_RS.off()
    # Write the command
    lcd_write_byte(data)
    time.sleep_ms(2)

def lcd_data(data):
    """Write data to the LCD controller"""
    # RS pin = 1, write to data register
    LCD_RS.on()
    # Write the data
    lcd_write_byte(data)

def lcd_init():
    """Initialization sequence of HD44780"""
    LCD_RS.off()     # These are all commands
    time.sleep_ms(20)
    lcd_write_nibble(0x30)
    time.sleep_ms(5)
    lcd_write_nibble(0x30)
    time.sleep_ms(1)
    lcd_write_nibble(0x30)
    time.sleep_ms(1)
    lcd_write_nibble(0x20)
    time.sleep_ms(1)
    lcd_command(0x28)    # 4-bit, 2 lines, 5x7 pixels
    lcd_command(0x06)    # increment, no shift
    lcd_command(0x01)    # clear display
    lcd_command(0x0F)    # display on, curson on and blinking


# Send initialization sequence
lcd_init()

# Infinite loop to blink "Hello" on the LCD
while True:
    # Write "Hello" on the LCD
    lcd_data(ord('H'))
    lcd_data(ord('e'))
    lcd_data(ord('l'))
    lcd_data(ord('l'))
    lcd_data(ord('o'))
    time.sleep_ms(1000)    # wait for 1 second
    lcd_command(1)         # clear display
    time.sleep_ms(1000)    # wait for 1 second then repeat