I have an 20x4 char LCD with an I2C convertor board. But when I'm connecting to it(I2C board), raspberry pi pico raises:
OSError: [Errno 5] EIO
I've double checked my wires - and my code too. and I've connected and disconnected many times but it didn't work
In internet wasn't any complete answer for that.
thanks.
lcd_api.py:
"""Provides an API for talking to HD44780 compatible character LCDs."""
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, 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.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.
self.implied_newline = False
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
# This is a default implementation of hal_sleep_us which is suitable
# for most micropython implementations. For platforms which don't
# support `time.sleep_us()` they should provide their own implementation
# of hal_sleep_us in their hal layer and it will be used instead.
def hal_sleep_us(self, usecs):
"""Sleep for some time (given in microseconds)."""
time.sleep_us(usecs) # NOTE this is not part of Standard Python library, specific hal layers will need to override this
i2cLcd.py(my library for connecting to i2c LCD)(I've chosen thin name for it):
import utime
import gc
from lcd_api import LcdApi
from machine import I2C
# PCF8574 pin definitions
MASK_RS = 0x01 # P0
MASK_RW = 0x02 # P1
MASK_E = 0x04 # P2
SHIFT_BACKLIGHT = 3 # P3
SHIFT_DATA = 4 # P4-P7
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 = i2c
self.i2c_addr = int(hex(i2c_addr))
self.i2c.writeto(self.i2c_addr, bytes([0]))
utime.sleep_ms(20) # Allow LCD time to powerup
# Send reset 3 times
self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
utime.sleep_ms(5) # Need to delay at least 4.1 msec
self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
utime.sleep_ms(1)
self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
utime.sleep_ms(1)
# Put LCD into 4-bit mode
self.hal_write_init_nibble(self.LCD_FUNCTION)
utime.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)
gc.collect()
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, bytes([byte | MASK_E]))
self.i2c.writeto(self.i2c_addr, bytes([byte]))
gc.collect()
def hal_backlight_on(self):
# Allows the hal layer to turn the backlight on
self.i2c.writeto(self.i2c_addr, bytes([1 << SHIFT_BACKLIGHT]))
gc.collect()
def hal_backlight_off(self):
#Allows the hal layer to turn the backlight off
self.i2c.writeto(self.i2c_addr, bytes([0]))
gc.collect()
def hal_write_command(self, cmd):
# Write 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 delay of 4.1 msec
utime.sleep_ms(5)
gc.collect()
def hal_write_data(self, data):
# Write data to the LCD. Data is latched on the falling edge of E.
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]))
gc.collect()
my part of code that raises error:
i2c = I2C(0, sda=Pin(8), scl=Pin(9), freq=400000)
I2C_ADDR = i2c.scan()[0]
lcd = I2cLcd(i2c, I2C_ADDR, 4, 20)
OSError: [Errno 5] EIO shows a communication problem, may be caused by wrong wirings or missing pull-up resistors in sda/scl lines.