from machine import Pin, SoftI2C, PWM
from utime import sleep_ms
from hcsr04 import HCSR04
from i2c_lcd import I2cLcd

# Initialize Ultrasonic Sensor
trig_pin = Pin(12, Pin.OUT)
echo_pin = Pin(14, Pin.IN)
ultrasonic = HCSR04(trig_pin, echo_pin)

# Initialize Servo Motor
servo_pin = Pin(13, Pin.OUT)
servo_pwm = PWM(servo_pin)
servo_pwm.freq(50)  # Set PWM frequency to 50Hz
servo_min_duty = 10  # Minimum duty cycle for servo (adjust as needed)
servo_max_duty = 90  # Maximum duty cycle for servo (adjust as needed)

# Initialize LCD
i2c = SoftI2C(sda=Pin(21), scl=Pin(22))
lcd = I2cLcd(i2c, 0x27, 2, 16)  # Adjust address and rows/columns if needed

def read_distance():
    try:
        distance = ultrasonic.distance_cm()
        return distance
    except OSError:
        return None

def activate_servo():
    # Move servo to a specific angle (adjust as needed)
    servo_pwm.duty(servo_min_duty)  # Move servo to minimum angle
    sleep_ms(500)  # Wait for servo to reach the position
    servo_pwm.duty(servo_max_duty)  # Move servo to maximum angle
    sleep_ms(500)  # Wait for servo to reach the position

while True:
    distance = read_distance()
    if distance is not None:
        print("Distance: %.2f cm" % distance)
        lcd.clear()
        #LCD Display
        lcd.move_to(0, 0)
        lcd.putstr('Distance: ')
        lcd.move_to(0, 1)
        lcd.putstr('%.2f cm' % distance)
        if distance < 100:
            activate_servo()
    sleep_ms(500)

main.py

diagram.json

"""Implements a HD44780 character LCD connected via PCF8574 on I2C. 
   This was tested with: https://www.wemos.cc/product/d1-mini.html""" 
from lcd_api import LcdApi 
from machine import I2C 
from time import sleep_ms 
# The PCF8574 has a jumper selectable address: 0x20 - 0x27 
#DEFAULT_I2C_ADDR = 0x20 
# 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 HD44780 character 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, bytearray([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 initialization. 
        """ 
        byte = ((nibble >> 4) & 0x0f) << SHIFT_DATA 
        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E])) 
        self.i2c.writeto(self.i2c_addr, bytearray([byte])) 
    def hal_backlight_on(self): 
        """Allows the hal layer to turn the backlight on.""" 
        self.i2c.writeto(self.i2c_addr, bytearray([1 << SHIFT_BACKLIGHT])) 
    def hal_backlight_off(self): 
        """Allows the hal layer to turn the backlight off.""" 
        self.i2c.writeto(self.i2c_addr, bytearray([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, bytearray([byte | MASK_E])) 
        self.i2c.writeto(self.i2c_addr, bytearray([byte])) 
        byte = ((self.backlight << SHIFT_BACKLIGHT) | ((cmd & 0x0f) << SHIFT_DATA)) 
        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E])) 
        self.i2c.writeto(self.i2c_addr, bytearray([byte])) 
        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.""" 
        byte = (MASK_RS | (self.backlight << SHIFT_BACKLIGHT) | (((data >> 4) & 0x0f) << SHIFT_DATA)) 
        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E])) 
        self.i2c.writeto(self.i2c_addr, bytearray([byte])) 
        byte = (MASK_RS | (self.backlight << SHIFT_BACKLIGHT) | ((data & 0x0f) << SHIFT_DATA)) 
        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E])) 
        self.i2c.writeto(self.i2c_addr, bytearray([byte]))

i2c_lcd.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


lcd_api.py

from machine import Pin, time_pulse_us
from utime import sleep_us

__version__ = '0.2.1'
__author__ = 'Roberto Sánchez'
__license__ = "Apache License 2.0. https://www.apache.org/licenses/LICENSE-2.0"

class HCSR04:
    """
    Driver to use the untrasonic sensor HC-SR04.
    The sensor range is between 2cm and 4m.

    The timeouts received listening to echo pin are converted to OSError('Out of range')

    """
    # echo_timeout_us is based in chip range limit (400cm)
    def __init__(self, trigger_pin, echo_pin, echo_timeout_us=500*2*30):
        """
        trigger_pin: Output pin to send pulses
        echo_pin: Readonly pin to measure the distance. The pin should be protected with 1k resistor
        echo_timeout_us: Timeout in microseconds to listen to echo pin. 
        By default is based in sensor limit range (4m)
        """
        self.echo_timeout_us = echo_timeout_us
        # Init trigger pin (out)
        self.trigger = Pin(trigger_pin, mode=Pin.OUT, pull=None)
        self.trigger.value(0)

        # Init echo pin (in)
        self.echo = Pin(echo_pin, mode=Pin.IN, pull=None)

    def _send_pulse_and_wait(self):
        """
        Send the pulse to trigger and listen on echo pin.
        We use the method `machine.time_pulse_us()` to get the microseconds until the echo is received.
        """
        self.trigger.value(0) # Stabilize the sensor
        sleep_us(5)
        self.trigger.value(1)
        # Send a 10us pulse.
        sleep_us(10)
        self.trigger.value(0)
        try:
            pulse_time = time_pulse_us(self.echo, 1, self.echo_timeout_us)
            # time_pulse_us returns -2 if there was timeout waiting for condition; and -1 if there was timeout during the main measurement. It DOES NOT raise an exception
            # ...as of MicroPython 1.17: http://docs.micropython.org/en/v1.17/library/machine.html#machine.time_pulse_us
            if pulse_time < 0:
                MAX_RANGE_IN_CM = const(500) # it's really ~400 but I've read people say they see it working up to ~460
                pulse_time = int(MAX_RANGE_IN_CM * 29.1) # 1cm each 29.1us
            return pulse_time
        except OSError as ex:
            if ex.args[0] == 110: # 110 = ETIMEDOUT
                raise OSError('Out of range')
            raise ex

    def distance_mm(self):
        """
        Get the distance in milimeters without floating point operations.
        """
        pulse_time = self._send_pulse_and_wait()

        # To calculate the distance we get the pulse_time and divide it by 2 
        # (the pulse walk the distance twice) and by 29.1 becasue
        # the sound speed on air (343.2 m/s), that It's equivalent to
        # 0.34320 mm/us that is 1mm each 2.91us
        # pulse_time // 2 // 2.91 -> pulse_time // 5.82 -> pulse_time * 100 // 582 
        mm = pulse_time * 100 // 582
        return mm

    def distance_cm(self):
        """
        Get the distance in centimeters with floating point operations.
        It returns a float
        """
        pulse_time = self._send_pulse_and_wait()

        # To calculate the distance we get the pulse_time and divide it by 2 
        # (the pulse walk the distance twice) and by 29.1 becasue
        # the sound speed on air (343.2 m/s), that It's equivalent to
        # 0.034320 cm/us that is 1cm each 29.1us
        cms = (pulse_time / 2) / 29.1
        return cms


hcsr04.py

from machine import Pin, PWM

class Servo:
    # these defaults work for the standard TowerPro SG90
    __servo_pwm_freq = 50
    __min_u10_duty = 26 - 0 # offset for correction
    __max_u10_duty = 123- 0  # offset for correction
    min_angle = 0
    max_angle = 180
    current_angle = 0.001


    def __init__(self, pin):
        self.__initialise(pin)


    def update_settings(self, servo_pwm_freq, min_u10_duty, max_u10_duty, min_angle, max_angle, pin):
        self.__servo_pwm_freq = servo_pwm_freq
        self.__min_u10_duty = min_u10_duty
        self.__max_u10_duty = max_u10_duty
        self.min_angle = min_angle
        self.max_angle = max_angle
        self.__initialise(pin)


    def move(self, angle):
        # round to 2 decimal places, so we have a chance of reducing unwanted servo adjustments
        angle = round(angle, 2)
        # do we need to move?
        if angle == self.current_angle:
            return
        self.current_angle = angle
        # calculate the new duty cycle and move the motor
        duty_u10 = self.__angle_to_u10_duty(angle)
        self.__motor.duty(duty_u10)

    def __angle_to_u10_duty(self, angle):
        return int((angle - self.min_angle) * self.__angle_conversion_factor) + self.__min_u10_duty


    def __initialise(self, pin):
        self.current_angle = -0.001
        self.__angle_conversion_factor = (self.__max_u10_duty - self.__min_u10_duty) / (self.max_angle - self.min_angle)
        self.__motor = PWM(Pin(pin))
        self.__motor.freq(self.__servo_pwm_freq)