
Raspberry Pi Pico Weather Station Using Dht11 Sensor
Table of Contents
Introduction
In this tutorial we will learn How to make Raspberry Pi Pico Weather Station using Dht11 Humidity Sensor, weather station to monitor the temperature and humidity in your home or office We will use 16×2 LCD Display and display the DHT11 temperature and Humidity value on it.
Raspberry Pi Pico Weather Station
The DHT11 Sensor is aa cheap cost digital temperature and humidity sensor.we used Raspberry Pi Pico board to read the temperature, humidity data of Dht11 Sensor. The data is displayed on a 16×2 LCD screen.
Materials Required
- Raspberry Pi Pico
- 16×2 LCD
- DHT11 Temperature and Humidity Sensor
- Jumper Wires
Schematics for Raspberry Pi Pico Weather Station
The hardware setup and Mapping guide for DHT11 Sensor with Raspberry Pi Pico board & 16×2 LCD is super easy. The connection diagram is given Below.
Connect the DHT11 digital output pin to GP15 of Raspberry Pi Pico Board. Connect the SCL & SDA pin of OLED Display to Raspberry Pi Pico GP27 & GP26 Pin. Supply DHT11 & 16×2 Display with VBUS(SV) VCC & Connect their GND(-) pins to Raspberry Pi Pico GND(-) Pin.
LCD -> Pico
- GND -> GND
- VCC -> VBUS(SV)
- SDA -> GP26
- SCL -> GP27
DHT11 -> Pico
- Vcc(+) -> 3.3V
- Out(o) -> GP15
- GND(-) -> GND
Source Code for Raspberry Pi Pico Weather Station
The code comprises of 4 parts:
- dht.py
- lcd_api.py
- pico_i2c_lcd.py
- main.py
dht.py
import array import micropython import utime from machine import Pin from micropython import const class InvalidChecksum(Exception): pass class InvalidPulseCount(Exception): pass MAX_UNCHANGED = const(100) MIN_INTERVAL_US = const(200000) HIGH_LEVEL = const(50) EXPECTED_PULSES = const(84) class DHT11: _temperature: float _humidity: float def __init__(self, pin): self._pin = pin self._last_measure = utime.ticks_us() self._temperature = -1 self._humidity = -1 def measure(self): current_ticks = utime.ticks_us() if utime.ticks_diff(current_ticks, self._last_measure) < MIN_INTERVAL_US and ( self._temperature > -1 or self._humidity > -1 ): # Less than a second since last read, which is too soon according # to the datasheet return self._send_init_signal() pulses = self._capture_pulses() buffer = self._convert_pulses_to_buffer(pulses) self._verify_checksum(buffer) self._humidity = buffer[0] + buffer[1] / 10 self._temperature = buffer[2] + buffer[3] / 10 self._last_measure = utime.ticks_us() @property def humidity(self): self.measure() return self._humidity @property def temperature(self): self.measure() return self._temperature def _send_init_signal(self): self._pin.init(Pin.OUT, Pin.PULL_DOWN) self._pin.value(1) utime.sleep_ms(50) self._pin.value(0) utime.sleep_ms(18) @micropython.native def _capture_pulses(self): pin = self._pin pin.init(Pin.IN, Pin.PULL_UP) val = 1 idx = 0 transitions = bytearray(EXPECTED_PULSES) unchanged = 0 timestamp = utime.ticks_us() while unchanged < MAX_UNCHANGED: if val != pin.value(): if idx >= EXPECTED_PULSES: raise InvalidPulseCount( "Got more than {} pulses".format(EXPECTED_PULSES) ) now = utime.ticks_us() transitions[idx] = now - timestamp timestamp = now idx += 1 val = 1 - val unchanged = 0 else: unchanged += 1 pin.init(Pin.OUT, Pin.PULL_DOWN) if idx != EXPECTED_PULSES: raise InvalidPulseCount( "Expected {} but got {} pulses".format(EXPECTED_PULSES, idx) ) return transitions[4:] def _convert_pulses_to_buffer(self, pulses): """Convert a list of 80 pulses into a 5 byte buffer The resulting 5 bytes in the buffer will be: 0: Integral relative humidity data 1: Decimal relative humidity data 2: Integral temperature data 3: Decimal temperature data 4: Checksum """ # Convert the pulses to 40 bits binary = 0 for idx in range(0, len(pulses), 2): binary = binary << 1 | int(pulses[idx] > HIGH_LEVEL) # Split into 5 bytes buffer = array.array("B") for shift in range(4, -1, -1): buffer.append(binary >> shift * 8 & 0xFF) return buffer def _verify_checksum(self, buffer): # Calculate checksum checksum = 0 for buf in buffer[0:4]: checksum += buf if checksum & 0xFF != buffer[4]: raise InvalidChecksum()
lcd_api.py
import time class LcdApi: 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. pass 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 def hal_sleep_us(self, usecs): """Sleep for some time (given in microseconds).""" time.sleep_us(usecs)
pico_i2c_lcd.py
from lcd_api import LcdApi from machine import I2C from time import sleep_ms DEFAULT_I2C_ADDR = 0x27 # 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 character based 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 intiialization. """ 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]))
main.py
from machine import Pin import utime as time from pico_i2c_lcd import I2cLcd from machine import I2C from dht import DHT11, InvalidChecksum i2c = I2C(id=1,scl=Pin(27),sda=Pin(26),freq=100000) lcd = I2cLcd(i2c, 0x27, 2, 16) while True: time.sleep(1) pin = Pin(15, Pin.OUT, Pin.PULL_DOWN) sensor = DHT11(pin) t = (sensor.temperature) h = (sensor.humidity) print("Temperature: {}".format(sensor.temperature)) print("Humidity: {}".format(sensor.humidity)) time.sleep(1) lcd.clear() lcd.move_to(0,0) lcd.putstr('Temp :') lcd.move_to(7,0) lcd.putstr(str(t)+" C") lcd.move_to(0,1) lcd.putstr('Humi :') lcd.move_to(7,1) lcd.putstr(str(h)+" %")