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lcd_api.py
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lcd_api.py
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# MIT License
# Copyright (c) 2023 Tyler Peppy
# https://github.com/T-622/RPI-PICO-I2C-LCD/blob/main/LICENSE.md
import time
class LcdApi:
# Implements the API for talking with HD44780 compatible character LCDs.
# This class only knows what commands to send to the LCD, and not how to get
# them to the LCD.
#
# It is expected that a derived class will implement the hal_xxx functions.
#
# The following constant names were lifted from the avrlib lcd.h header file,
# with bit numbers changed to bit masks.
# HD44780 LCD controller command set
LCD_CLR = 0x01 # DB0: clear display
LCD_HOME = 0x02 # DB1: return to home position
LCD_ENTRY_MODE = 0x04 # DB2: set entry mode
LCD_ENTRY_INC = 0x02 # DB1: increment
LCD_ENTRY_SHIFT = 0x01 # DB0: shift
LCD_ON_CTRL = 0x08 # DB3: turn lcd/cursor on
LCD_ON_DISPLAY = 0x04 # DB2: turn display on
LCD_ON_CURSOR = 0x02 # DB1: turn cursor on
LCD_ON_BLINK = 0x01 # DB0: blinking cursor
LCD_MOVE = 0x10 # DB4: move cursor/display
LCD_MOVE_DISP = 0x08 # DB3: move display (0-> move cursor)
LCD_MOVE_RIGHT = 0x04 # DB2: move right (0-> left)
LCD_FUNCTION = 0x20 # DB5: function set
LCD_FUNCTION_8BIT = 0x10 # DB4: set 8BIT mode (0->4BIT mode)
LCD_FUNCTION_2LINES = 0x08 # DB3: two lines (0->one line)
LCD_FUNCTION_10DOTS = 0x04 # DB2: 5x10 font (0->5x7 font)
LCD_FUNCTION_RESET = 0x30 # See "Initializing by Instruction" section
LCD_CGRAM = 0x40 # DB6: set CG RAM address
LCD_DDRAM = 0x80 # DB7: set DD RAM address
LCD_RS_CMD = 0
LCD_RS_DATA = 1
LCD_RW_WRITE = 0
LCD_RW_READ = 1
def __init__(self, num_lines, num_columns):
self.num_lines = num_lines
if self.num_lines > 4:
self.num_lines = 4
self.num_columns = num_columns
if self.num_columns > 40:
self.num_columns = 40
self.cursor_x = 0
self.cursor_y = 0
self.implied_newline = False
self.backlight = True
self.display_off()
self.backlight_on()
self.clear()
self.hal_write_command(self.LCD_ENTRY_MODE | self.LCD_ENTRY_INC)
self.hide_cursor()
self.display_on()
def clear(self):
# Clears the LCD display and moves the cursor to the top left corner
self.hal_write_command(self.LCD_CLR)
self.hal_write_command(self.LCD_HOME)
self.cursor_x = 0
self.cursor_y = 0
def show_cursor(self):
# Causes the cursor to be made visible
self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY |
self.LCD_ON_CURSOR)
def hide_cursor(self):
# Causes the cursor to be hidden
self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY)
def blink_cursor_on(self):
# Turns on the cursor, and makes it blink
self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY |
self.LCD_ON_CURSOR | self.LCD_ON_BLINK)
def blink_cursor_off(self):
# Turns on the cursor, and makes it no blink (i.e. be solid)
self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY |
self.LCD_ON_CURSOR)
def display_on(self):
# Turns on (i.e. unblanks) the LCD
self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY)
def display_off(self):
# Turns off (i.e. blanks) the LCD
self.hal_write_command(self.LCD_ON_CTRL)
def backlight_on(self):
# Turns the backlight on.
# This isn't really an LCD command, but some modules have backlight
# controls, so this allows the hal to pass through the command.
self.backlight = True
self.hal_backlight_on()
def backlight_off(self):
# Turns the backlight off.
# This isn't really an LCD command, but some modules have backlight
# controls, so this allows the hal to pass through the command.
self.backlight = False
self.hal_backlight_off()
def move_to(self, cursor_x, cursor_y):
# Moves the cursor position to the indicated position. The cursor
# position is zero based (i.e. cursor_x == 0 indicates first column).
self.cursor_x = cursor_x
self.cursor_y = cursor_y
addr = cursor_x & 0x3f
if cursor_y & 1:
addr += 0x40 # Lines 1 & 3 add 0x40
if cursor_y & 2: # Lines 2 & 3 add number of columns
addr += self.num_columns
self.hal_write_command(self.LCD_DDRAM | addr)
def putchar(self, char):
# Writes the indicated character to the LCD at the current cursor
# position, and advances the cursor by one position.
if char == '\n':
if self.implied_newline:
# self.implied_newline means we advanced due to a wraparound,
# so if we get a newline right after that we ignore it.
pass
else:
self.cursor_x = self.num_columns
else:
self.hal_write_data(ord(char))
self.cursor_x += 1
if self.cursor_x >= self.num_columns:
self.cursor_x = 0
self.cursor_y += 1
self.implied_newline = (char != '\n')
if self.cursor_y >= self.num_lines:
self.cursor_y = 0
self.move_to(self.cursor_x, self.cursor_y)
def putstr(self, string):
# Write the indicated string to the LCD at the current cursor
# position and advances the cursor position appropriately.
for char in string:
self.putchar(char)
def custom_char(self, location, charmap):
# Write a character to one of the 8 CGRAM locations, available
# as chr(0) through chr(7).
location &= 0x7
self.hal_write_command(self.LCD_CGRAM | (location << 3))
self.hal_sleep_us(40)
for i in range(8):
self.hal_write_data(charmap[i])
self.hal_sleep_us(40)
self.move_to(self.cursor_x, self.cursor_y)
def hal_backlight_on(self):
# Allows the hal layer to turn the backlight on.
# If desired, a derived HAL class will implement this function.
pass
def hal_backlight_off(self):
# Allows the hal layer to turn the backlight off.
# If desired, a derived HAL class will implement this function.
pass
def hal_write_command(self, cmd):
# Write a command to the LCD.
# It is expected that a derived HAL class will implement this function.
raise NotImplementedError
def hal_write_data(self, data):
# Write data to the LCD.
# It is expected that a derived HAL class will implement this function.
raise NotImplementedError
def hal_sleep_us(self, usecs):
# Sleep for some time (given in microseconds)
time.sleep_us(usecs)