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Gestion de l'interface I2C pour le lcd à nommer pico_i2c_lcd.py
import
utime
from
lcd_api
import
from
machine
import
# PCF8574 pin definitions
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
=
i2c
self.i2c_addr
self.i2c.writeto(self.i2c_addr, bytes([0]))
utime.sleep_ms(20)
# Send reset 3 times
self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
utime.sleep_ms(5)
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
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, 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):
# 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)
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]))
LcdApi
I2C
# P0
# P1
# P2
# P3
# P4-P7
=
i2c_addr
# Allow LCD time to powerup
# Need to delay at least 4.1 msec
> 1:
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