"""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()