Thank you for providing this code. I am now able to run my 20x4 display on an ESP32 ...
KR Bernd
[quote=sequel post_id=14375 time=1475289361 user_id=1911]
Hi Electra,
So sorry for the late reply.
Here is the code,
esp8266_i2c_lcd.py :
[code]
"""Implements a character based lcd connected via PCF8574 on i2c."""
from lcd import LcdApi
from machine import I2C
from time import sleep_ms
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 character based lcd connected via PCF8574 on i2c."""
def __init__(self, i2c, i2c_addr, num_lines, num_columns):
self.i2c = i2c
self.i2c_addr = i2c_addr
self.i2c.writeto(self.i2c_addr, bytes([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 intiialization.
"""
byte=((nibble >> 4) & 0x0f) << SHIFT_DATA
self.i2c.writeto(self.i2c_addr, bytes([byte | MASK_E]))
self.i2c.writeto(self.i2c_addr, bytes([byte]))
def hal_backlight_on(self):
"""Allows the hal layer to turn the backlight on."""
self.i2c.writeto(self.i2c_addr, bytes([1 << SHIFT_BACKLIGHT]))
def hal_backlight_off(self):
"""Allows the hal layer to turn the backlight off."""
self.i2c.writeto(self.i2c_addr, bytes([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, bytes([byte | MASK_E]))
self.i2c.writeto(self.i2c_addr, bytes([byte]))
byte=((self.backlight << SHIFT_BACKLIGHT) |
((cmd & 0x0f) << SHIFT_DATA))
self.i2c.writeto(self.i2c_addr, bytes([byte | MASK_E]))
self.i2c.writeto(self.i2c_addr, bytes([byte]))
if cmd <= 3:
# The home and clear commands require a worst
# case sleep_ms 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, bytes([byte | MASK_E]))
self.i2c.writeto(self.i2c_addr, bytes([byte]))
byte=(MASK_RS |
(self.backlight << SHIFT_BACKLIGHT) |
((data & 0x0f) << SHIFT_DATA))
self.i2c.writeto(self.i2c_addr, bytes([byte | MASK_E]))
self.i2c.writeto(self.i2c_addr, bytes([byte]))
[/code]
lcd.py :
[code]
"""Provides an API for talking to HD44780 style character LCDs."""
class LcdApi(object):
"""Implements the API for talking with n LCD. This class only knows what
commands to send to the LCD, and not how t 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, however, I changed the definitions from bit numbers
# 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.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:
addr += 0x14 # Lines 2 & 3 add 0x14
self.hal_write_command(self.LCD_DDRAM | addr)
def putchar(self, char):
"""Writes the indicated charcter to the LCD at the current cursor
position, and advances the cursor by one position.
"""
if self.cursor_x >= self.num_columns or char == '\n':
self.cursor_x = 0
self.cursor_y += 1
if self.cursor_y >= self.num_lines:
self.cursor_y = 0
self.move_to(self.cursor_x, self.cursor_y)
if char != '\n':
self.hal_write_data(ord(char))
self.cursor_x += 1
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 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
[/code]
[/quote]