dht20.py

from machine import Pin, I2C
from utime import sleep

import time

from utime import sleep_ms


import utime
import gc

# 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 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


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, 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()



class DHT20:
    """Class for the DHT20 Temperature and Humidity Sensor.
    The datasheet can be found at http://www.aosong.com/userfiles/files/media/Data%20Sheet%20DHT20%20%20A1.pdf
    """
    def __init__(self, address: int, i2c: I2C):
        self._address = address
        self._i2c = i2c
        sleep_ms(100)
        if not self.is_ready:
            self._initialize()
            sleep_ms(100)
            if not self.is_ready:
                raise RuntimeError("Could not initialize the DHT20.")
    @property
    def is_ready(self) -> bool:
        """Check if the DHT20 is ready."""
        self._i2c.writeto(self._address, bytearray(b'\x71'))
        return self._i2c.readfrom(self._address, 1)[0] == 0x18
    def _initialize(self):
        buffer = bytearray(b'\x00\x00')
        self._i2c.writeto_mem(self._address, 0x1B, buffer)
        self._i2c.writeto_mem(self._address, 0x1C, buffer)
        self._i2c.writeto_mem(self._address, 0x1E, buffer)
    def _trigger_measurements(self):
        self._i2c.writeto_mem(self._address, 0xAC, bytearray(b'\x33\x00'))
    def _read_measurements(self):
        buffer = self._i2c.readfrom(self._address, 7)
        return buffer, buffer[0] & 0x80 == 0
    def _crc_check(self, input_bitstring: str, check_value: str) -> bool:
        """Calculate the CRC check of a string of bits using a fixed polynomial.

        See https://en.wikipedia.org/wiki/Cyclic_redundancy_check
            https://xcore.github.io/doc_tips_and_tricks/crc.html#the-initial-value

        Keyword arguments:
        input_bitstring -- the data to verify
        check_value -- the CRC received with the data
        """
        polynomial_bitstring = "100110001"
        len_input = len(input_bitstring)
        initial_padding = check_value
        input_padded_array = list(input_bitstring + initial_padding)
        while '1' in input_padded_array[:len_input]:
            cur_shift = input_padded_array.index('1')
            for i in range(len(polynomial_bitstring)):
                input_padded_array[cur_shift + i] = \
                    str(int(polynomial_bitstring[i] != input_padded_array[cur_shift + i]))
        return '1' not in ''.join(input_padded_array)[len_input:]
    @property
    def measurements(self) -> dict:
        """Get the temperature (°C) and relative humidity (%RH).

        Returns a dictionary with the most recent measurements.
        't': temperature (°C),
        't_adc': the 'raw' temperature as produced by the ADC,
        'rh': relative humidity (%RH),
        'rh_adc': the 'raw' relative humidity as produced by the ADC,
        'crc_ok': indicates if the data was received correctly
        """
        self._trigger_measurements()
        sleep_ms(50)
        data = self._read_measurements()
        retry = 3
        while not data[1]:
            if not retry:
                raise RuntimeError("Could not read measurements from the DHT20.")
            sleep_ms(10)
            data = self._read_measurements()
            retry -= 1
        buffer = data[0]
        s_rh = buffer[1] << 12 | buffer[2] << 4 | buffer[3] >> 4
        s_t = (buffer[3] << 16 | buffer[4] << 8 | buffer[5]) & 0xfffff
        rh = (s_rh / 2 ** 20) * 100
        t = ((s_t / 2 ** 20) * 200) - 50
        crc_ok = self._crc_check(
            f"{buffer[0] ^ 0xFF:08b}{buffer[1]:08b}{buffer[2]:08b}{buffer[3]:08b}{buffer[4]:08b}{buffer[5]:08b}",
            f"{buffer[6]:08b}")
        return {
            't': t,
            't_adc': s_t,
            'rh': rh,
            'rh_adc': s_rh,
            'crc_ok': crc_ok
        }


i2c0_sda = Pin(8)
i2c0_scl = Pin(9)
i2c0 = I2C(0, sda=i2c0_sda, scl=i2c0_scl)

dht20 = DHT20(0x38, i2c0)

lcd = I2cLcd(i2c0, 0x3e, 2, 16)

opto = Pin(22, Pin.IN, Pin.PULL_UP)

elapsed = 0
opto_status = 0
last_tick_opto_status = 0
trigger_refresh = 0

since_tmp_refresh = 0

cur = "0.00 km/h"

measurements = dht20.measurements

while True:
    if since_tmp_refresh > 5000:
        measurements = dht20.measurements
        print(f"Temperature: {measurements['t']} °C, humidity: {measurements['rh']} %RH")
        since_tmp_refresh = 0
    opto_status = opto.value()
    if (opto_status):
        if not last_tick_opto_status and (elapsed > 200):
            last_tick_opto_status = 1
            speed = 2170 / 1 / elapsed * 3.6
            cur = f"{speed:.2f}"
            elapsed = 0
            print(f"Current speed is {cur}\n")
    else:
        last_tick_opto_status = 0
    if trigger_refresh > 500:
        lcd.clear()
        lcd.putstr(f"Speed: {cur}\n")
        lcd.putstr(f"Tmp: {measurements['t']:.1f} Rh: {measurements['rh']:.1f}")
        trigger_refresh = 0
    sleep_ms(1)
    elapsed += 1
    trigger_refresh += 1
    since_tmp_refresh += 1