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"""Implements a HD44780 character LCD connected via NodeMCU GPIO pins."""
from lcd_api import LcdApi
from machine import Pin
from utime import sleep_ms, sleep_us
class GpioLcd(LcdApi):
"""Implements a HD44780 character LCD connected via NodeMCU GPIO pins."""
def __init__(self, rs_pin, enable_pin, d0_pin=None, d1_pin=None,
d2_pin=None, d3_pin=None, d4_pin=None, d5_pin=None,
d6_pin=None, d7_pin=None, rw_pin=None, backlight_pin=None,
num_lines=2, num_columns=16):
"""Constructs the GpioLcd object. All of the arguments must be Pin
objects which describe which pin the given line from the LCD is
connected to.
When used in 4-bit mode, only D4, D5, D6, and D7 are physically
connected to the LCD panel. This function allows you call it like
GpioLcd(rs, enable, D4, D5, D6, D7) and it will interpret that as
if you had actually called:
GpioLcd(rs, enable, d4=D4, d5=D5, d6=D6, d7=D7)
The enable 8-bit mode, you need pass d0 through d7.
The rw pin isn't used by this library, but if you specify it, then
it will be set low.
"""
self.rs_pin = rs_pin
self.enable_pin = enable_pin
self.rw_pin = rw_pin
self.backlight_pin = backlight_pin
self._4bit = True
if d4_pin and d5_pin and d6_pin and d7_pin:
self.d0_pin = d0_pin
self.d1_pin = d1_pin
self.d2_pin = d2_pin
self.d3_pin = d3_pin
self.d4_pin = d4_pin
self.d5_pin = d5_pin
self.d6_pin = d6_pin
self.d7_pin = d7_pin
if self.d0_pin and self.d1_pin and self.d2_pin and self.d3_pin:
self._4bit = False
else:
# This is really 4-bit mode, and the 4 data pins were just
# passed as the first 4 arguments, so we switch things around.
self.d0_pin = None
self.d1_pin = None
self.d2_pin = None
self.d3_pin = None
self.d4_pin = d0_pin
self.d5_pin = d1_pin
self.d6_pin = d2_pin
self.d7_pin = d3_pin
self.rs_pin.init(Pin.OUT)
self.rs_pin.value(0)
if self.rw_pin:
self.rw_pin.init(Pin.OUT)
self.rw_pin.value(0)
self.enable_pin.init(Pin.OUT)
self.enable_pin.value(0)
self.d4_pin.init(Pin.OUT)
self.d5_pin.init(Pin.OUT)
self.d6_pin.init(Pin.OUT)
self.d7_pin.init(Pin.OUT)
self.d4_pin.value(0)
self.d5_pin.value(0)
self.d6_pin.value(0)
self.d7_pin.value(0)
if not self._4bit:
self.d0_pin.init(Pin.OUT)
self.d1_pin.init(Pin.OUT)
self.d2_pin.init(Pin.OUT)
self.d3_pin.init(Pin.OUT)
self.d0_pin.value(0)
self.d1_pin.value(0)
self.d2_pin.value(0)
self.d3_pin.value(0)
if self.backlight_pin is not None:
self.backlight_pin.init(Pin.OUT)
self.backlight_pin.value(0)
# See about splitting this into begin
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)
cmd = self.LCD_FUNCTION
if not self._4bit:
cmd |= self.LCD_FUNCTION_8BIT
self.hal_write_init_nibble(cmd)
sleep_ms(1)
LcdApi.__init__(self, num_lines, num_columns)
if num_lines > 1:
cmd |= self.LCD_FUNCTION_2LINES
self.hal_write_command(cmd)
def hal_pulse_enable(self):
"""Pulse the enable line high, and then low again."""
self.enable_pin.value(0)
sleep_us(1)
self.enable_pin.value(1)
sleep_us(1) # Enable pulse needs to be > 450 nsec
self.enable_pin.value(0)
sleep_us(100) # Commands need > 37us to settle
def hal_write_init_nibble(self, nibble):
"""Writes an initialization nibble to the LCD.
This particular function is only used during initialization.
"""
self.hal_write_4bits(nibble >> 4)
def hal_backlight_on(self):
"""Allows the hal layer to turn the backlight on."""
if self.backlight_pin:
self.backlight_pin.value(1)
def hal_backlight_off(self):
"""Allows the hal layer to turn the backlight off."""
if self.backlight_pin:
self.backlight_pin.value(0)
def hal_write_command(self, cmd):
"""Writes a command to the LCD.
Data is latched on the falling edge of E.
"""
self.rs_pin.value(0)
self.hal_write_8bits(cmd)
if cmd <= 3:
# The home and clear commands require a worst
# case delay of 4.1 msec
sleep_ms(5)
def hal_write_data(self, data):
"""Write data to the LCD."""
self.rs_pin.value(1)
self.hal_write_8bits(data)
def hal_write_8bits(self, value):
"""Writes 8 bits of data to the LCD."""
if self.rw_pin:
self.rw_pin.value(0)
if self._4bit:
self.hal_write_4bits(value >> 4)
self.hal_write_4bits(value)
else:
self.d3_pin.value(value & 0x08)
self.d2_pin.value(value & 0x04)
self.d1_pin.value(value & 0x02)
self.d0_pin.value(value & 0x01)
self.hal_write_4bits(value >> 4)
def hal_write_4bits(self, nibble):
"""Writes 4 bits of data to the LCD."""
self.d7_pin.value(nibble & 0x08)
self.d6_pin.value(nibble & 0x04)
self.d5_pin.value(nibble & 0x02)
self.d4_pin.value(nibble & 0x01)
self.hal_pulse_enable()
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