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.

Raspberry Pi

Tutorial de Rapberry Pi en español.
- Juan Antonio Villalpando -

Volver al índice del tutorial

____________________________

5.- Pantalla LCD con bus I2C.

GPIO2 es SDA
GPIO3 es SCL

______________________________
1.- Conexión.

http://www.circuitbasics.com/raspberry-pi-i2c-lcd-set-up-and-programming/

- Habilitamos el reconocimiento de I2C, para ello escribimos

$ sudo su
# raspi-config

- Seleccionamos lo indicado en las siguientes imágenes.

- Instalación de herramientas para obtener la dirección I2C de la pantalla LCD.

- Mediante este programa podremos obtener la dirección de los dispositivos conectado al bus I2C.

$ sudo su
# apt-get install i2c-tool

- Instalamos la librería para acceder al bus I2C:

# apt-get install python-smbus

- Conectamos nuestra la pantalla LCD al bus I2C. Para detectar la dirección I2C de nuestra pantalla LCD escribimos:

# i2cdetect -y 1

- La dirección I2C de esta pantalla LCD es la 27.

_____________________
- Librería.

[ https://gist.github.com/DenisFromHR/cc863375a6e19dce359d ]

- Crea un archivo llamado I2C_LCD_driver.py y copia el contenido siguiente.

- Este archivo deberá estar en la misma carpeta que las aplicaciones realizadas para la pantalla LCD.

- Observa la LCD Address es la 0x27

I2C_LCD_driver.py

# -*- coding: utf-8 -*-
# Original code found at:
# https://gist.github.com/DenisFromHR/cc863375a6e19dce359d

"""
Compiled, mashed and generally mutilated 2014-2015 by Denis Pleic
Made available under GNU GENERAL PUBLIC LICENSE

# Modified Python I2C library for Raspberry Pi
# as found on http://www.recantha.co.uk/blog/?p=4849
# Joined existing 'i2c_lib.py' and 'lcddriver.py' into a single library
# added bits and pieces from various sources
# By DenisFromHR (Denis Pleic)
# 2015-02-10, ver 0.1

"""

# i2c bus (0 -- original Pi, 1 -- Rev 2 Pi)
I2CBUS = 1

# LCD Address
ADDRESS = 0x27

import smbus
from time import sleep

class i2c_device:
   def __init__(self, addr, port=I2CBUS):
      self.addr = addr
      self.bus = smbus.SMBus(port)

# Write a single command
   def write_cmd(self, cmd):
      self.bus.write_byte(self.addr, cmd)
      sleep(0.0001)

# Write a command and argument
   def write_cmd_arg(self, cmd, data):
      self.bus.write_byte_data(self.addr, cmd, data)
      sleep(0.0001)

# Write a block of data
   def write_block_data(self, cmd, data):
      self.bus.write_block_data(self.addr, cmd, data)
      sleep(0.0001)

# Read a single byte
   def read(self):
      return self.bus.read_byte(self.addr)

# Read
   def read_data(self, cmd):
      return self.bus.read_byte_data(self.addr, cmd)

# Read a block of data
   def read_block_data(self, cmd):
      return self.bus.read_block_data(self.addr, cmd)


# commands
LCD_CLEARDISPLAY = 0x01
LCD_RETURNHOME = 0x02
LCD_ENTRYMODESET = 0x04
LCD_DISPLAYCONTROL = 0x08
LCD_CURSORSHIFT = 0x10
LCD_FUNCTIONSET = 0x20
LCD_SETCGRAMADDR = 0x40
LCD_SETDDRAMADDR = 0x80

# flags for display entry mode
LCD_ENTRYRIGHT = 0x00
LCD_ENTRYLEFT = 0x02
LCD_ENTRYSHIFTINCREMENT = 0x01
LCD_ENTRYSHIFTDECREMENT = 0x00

# flags for display on/off control
LCD_DISPLAYON = 0x04
LCD_DISPLAYOFF = 0x00
LCD_CURSORON = 0x02
LCD_CURSOROFF = 0x00
LCD_BLINKON = 0x01
LCD_BLINKOFF = 0x00

# flags for display/cursor shift
LCD_DISPLAYMOVE = 0x08
LCD_CURSORMOVE = 0x00
LCD_MOVERIGHT = 0x04
LCD_MOVELEFT = 0x00

# flags for function set
LCD_8BITMODE = 0x10
LCD_4BITMODE = 0x00
LCD_2LINE = 0x08
LCD_1LINE = 0x00
LCD_5x10DOTS = 0x04
LCD_5x8DOTS = 0x00

# flags for backlight control
LCD_BACKLIGHT = 0x08
LCD_NOBACKLIGHT = 0x00

En = 0b00000100 # Enable bit
Rw = 0b00000010 # Read/Write bit
Rs = 0b00000001 # Register select bit

class lcd:
   #initializes objects and lcd
   def __init__(self):
      self.lcd_device = i2c_device(ADDRESS)

      self.lcd_write(0x03)
      self.lcd_write(0x03)
      self.lcd_write(0x03)
      self.lcd_write(0x02)

      self.lcd_write(LCD_FUNCTIONSET | LCD_2LINE | LCD_5x8DOTS | LCD_4BITMODE)
      self.lcd_write(LCD_DISPLAYCONTROL | LCD_DISPLAYON)
      self.lcd_write(LCD_CLEARDISPLAY)
      self.lcd_write(LCD_ENTRYMODESET | LCD_ENTRYLEFT)
      sleep(0.2)


   # clocks EN to latch command
   def lcd_strobe(self, data):
      self.lcd_device.write_cmd(data | En | LCD_BACKLIGHT)
      sleep(.0005)
      self.lcd_device.write_cmd(((data & ~En) | LCD_BACKLIGHT))
      sleep(.0001)

   def lcd_write_four_bits(self, data):
      self.lcd_device.write_cmd(data | LCD_BACKLIGHT)
      self.lcd_strobe(data)

   # write a command to lcd
   def lcd_write(self, cmd, mode=0):
      self.lcd_write_four_bits(mode | (cmd & 0xF0))
      self.lcd_write_four_bits(mode | ((cmd << 4) & 0xF0))

   # write a character to lcd (or character rom) 0x09: backlight | RS=DR<
   # works!
   def lcd_write_char(self, charvalue, mode=1):
      self.lcd_write_four_bits(mode | (charvalue & 0xF0))
      self.lcd_write_four_bits(mode | ((charvalue << 4) & 0xF0))
  
   # put string function with optional char positioning
   def lcd_display_string(self, string, line=1, pos=0):
    if line == 1:
      pos_new = pos
    elif line == 2:
      pos_new = 0x40 + pos
    elif line == 3:
      pos_new = 0x14 + pos
    elif line == 4:
      pos_new = 0x54 + pos

    self.lcd_write(0x80 + pos_new)

    for char in string:
      self.lcd_write(ord(char), Rs)

   # clear lcd and set to home
   def lcd_clear(self):
      self.lcd_write(LCD_CLEARDISPLAY)
      self.lcd_write(LCD_RETURNHOME)

   # define backlight on/off (lcd.backlight(1); off= lcd.backlight(0)
   def backlight(self, state): # for state, 1 = on, 0 = off
      if state == 1:
         self.lcd_device.write_cmd(LCD_BACKLIGHT)
      elif state == 0:
         self.lcd_device.write_cmd(LCD_NOBACKLIGHT)

   # add custom characters (0 - 7)
   def lcd_load_custom_chars(self, fontdata):
      self.lcd_write(0x40);
      for char in fontdata:
         for line in char:
            self.lcd_write_char(line)         
         

______________________________
2.- Códigos.

hola.py

import I2C_LCD_driver
from time import *

mylcd = I2C_LCD_driver.lcd()

mylcd.lcd_display_string("Hola mundo.", 1)

- "Hola mundo" comienza en la fila 2, columna 3.

hola_2.py

import I2C_LCD_driver
from time import *

mylcd = I2C_LCD_driver.lcd()

mylcd.lcd_display_string("Hola mundo.", 2, 3)

- Limpiar pantalla.

limpia.py

import I2C_LCD_driver
from time import *

mylcd = I2C_LCD_driver.lcd()

mylcd.lcd_display_string("Texto en pantalla", 1)
sleep(1)

mylcd.lcd_clear()

mylcd.lcd_display_string("Limpia pantalla", 1)
sleep(1)

mylcd.lcd_clear()

 

parpadeo.py

import time
import I2C_LCD_driver
mylcd = I2C_LCD_driver.lcd()

while True:
    mylcd.lcd_display_string(u"Hola mundo.")
    time.sleep(1)
    mylcd.lcd_clear()
    time.sleep(1)

- Fecha y hora.

fecha.py

import I2C_LCD_driver
import time
mylcd = I2C_LCD_driver.lcd()


while True:
    mylcd.lcd_display_string("Hora: %s" %time.strftime("%H:%M:%S"), 1)
    
    mylcd.lcd_display_string("Fecha: %s" %time.strftime("%m/%d/%Y"), 2)

- Dirección IP.

ip.py

import I2C_LCD_driver
import subprocess

mylcd = I2C_LCD_driver.lcd()

IP = subprocess.check_output(["hostname", "-I"]).split()[0]

mylcd.lcd_display_string("IP:", 1) 
mylcd.lcd_display_string(str(IP),2)

- Otras formas de ver la IP desde el terminal
ifconfig wlan0 | grep init | awk ‘{print $2}’
hostname -I

- Desplazamiento de caracteres y caracteres personalizados, lo puedes encontrar en:

http://www.circuitbasics.com/raspberry-pi-i2c-lcd-set-up-and-programming/

__________________________________________________
- Sensor de Temperatura y Humedad DHT11. Pantalla LCD. Librería dht11.

temperatura.py

import RPi.GPIO as GPIO
import dht11
import I2C_LCD_driver

from time import *

mylcd = I2C_LCD_driver.lcd()

GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)
GPIO.cleanup()

while True:
  
  instance = dht11.DHT11(pin = 4)
  result = instance.read()

# Uncomment for Fahrenheit:
# result.temperature = (result.temperature * 1.8) + 32 

  if result.is_valid():
    mylcd.lcd_display_string("Temp: %d%s C" % (result.temperature, chr(223)), 1)
    mylcd.lcd_display_string("Humidity: %d %%" % result.humidity, 2)
    

- Para el código anterior utilizaremos la librería dht11 obtenida de...

https://github.com/szazo/DHT11_Python/blob/master/dht11.py

- Este archivo de librería debe estar en el mismo directorio que el archivo anterior temperatura.py

dht11.py

import time
import RPi


class DHT11Result:
    'DHT11 sensor result returned by DHT11.read() method'

    ERR_NO_ERROR = 0
    ERR_MISSING_DATA = 1
    ERR_CRC = 2

    error_code = ERR_NO_ERROR
    temperature = -1
    humidity = -1

    def __init__(self, error_code, temperature, humidity):
        self.error_code = error_code
        self.temperature = temperature
        self.humidity = humidity

    def is_valid(self):
        return self.error_code == DHT11Result.ERR_NO_ERROR


class DHT11:
    'DHT11 sensor reader class for Raspberry'

    __pin = 0

    def __init__(self, pin):
        self.__pin = pin

    def read(self):
        RPi.GPIO.setup(self.__pin, RPi.GPIO.OUT)

        # send initial high
        self.__send_and_sleep(RPi.GPIO.HIGH, 0.05)

        # pull down to low
        self.__send_and_sleep(RPi.GPIO.LOW, 0.02)

        # change to input using pull up
        RPi.GPIO.setup(self.__pin, RPi.GPIO.IN, RPi.GPIO.PUD_UP)

        # collect data into an array
        data = self.__collect_input()

        # parse lengths of all data pull up periods
        pull_up_lengths = self.__parse_data_pull_up_lengths(data)

        # if bit count mismatch, return error (4 byte data + 1 byte checksum)
        if len(pull_up_lengths) != 40:
            return DHT11Result(DHT11Result.ERR_MISSING_DATA, 0, 0)

        # calculate bits from lengths of the pull up periods
        bits = self.__calculate_bits(pull_up_lengths)

        # we have the bits, calculate bytes
        the_bytes = self.__bits_to_bytes(bits)

        # calculate checksum and check
        checksum = self.__calculate_checksum(the_bytes)
        if the_bytes[4] != checksum:
            return DHT11Result(DHT11Result.ERR_CRC, 0, 0)

        # ok, we have valid data, return it
        return DHT11Result(DHT11Result.ERR_NO_ERROR, the_bytes[2], the_bytes[0])

    def __send_and_sleep(self, output, sleep):
        RPi.GPIO.output(self.__pin, output)
        time.sleep(sleep)

    def __collect_input(self):
        # collect the data while unchanged found
        unchanged_count = 0

        # this is used to determine where is the end of the data
        max_unchanged_count = 100

        last = -1
        data = []
        while True:
            current = RPi.GPIO.input(self.__pin)
            data.append(current)
            if last != current:
                unchanged_count = 0
                last = current
            else:
                unchanged_count += 1
                if unchanged_count > max_unchanged_count:
                    break

        return data

    def __parse_data_pull_up_lengths(self, data):
        STATE_INIT_PULL_DOWN = 1
        STATE_INIT_PULL_UP = 2
        STATE_DATA_FIRST_PULL_DOWN = 3
        STATE_DATA_PULL_UP = 4
        STATE_DATA_PULL_DOWN = 5

        state = STATE_INIT_PULL_DOWN

        lengths = [] # will contain the lengths of data pull up periods
        current_length = 0 # will contain the length of the previous period

        for i in range(len(data)):

            current = data[i]
            current_length += 1

            if state == STATE_INIT_PULL_DOWN:
                if current == RPi.GPIO.LOW:
                    # ok, we got the initial pull down
                    state = STATE_INIT_PULL_UP
                    continue
                else:
                    continue
            if state == STATE_INIT_PULL_UP:
                if current == RPi.GPIO.HIGH:
                    # ok, we got the initial pull up
                    state = STATE_DATA_FIRST_PULL_DOWN
                    continue
                else:
                    continue
            if state == STATE_DATA_FIRST_PULL_DOWN:
                if current == RPi.GPIO.LOW:
                    # we have the initial pull down, the next will be the data pull up
                    state = STATE_DATA_PULL_UP
                    continue
                else:
                    continue
            if state == STATE_DATA_PULL_UP:
                if current == RPi.GPIO.HIGH:
                    # data pulled up, the length of this pull up will determine whether it is 0 or 1
                    current_length = 0
                    state = STATE_DATA_PULL_DOWN
                    continue
                else:
                    continue
            if state == STATE_DATA_PULL_DOWN:
                if current == RPi.GPIO.LOW:
                    # pulled down, we store the length of the previous pull up period
                    lengths.append(current_length)
                    state = STATE_DATA_PULL_UP
                    continue
                else:
                    continue

        return lengths

    def __calculate_bits(self, pull_up_lengths):
        # find shortest and longest period
        shortest_pull_up = 1000
        longest_pull_up = 0

        for i in range(0, len(pull_up_lengths)):
            length = pull_up_lengths[i]
            if length < shortest_pull_up:
                shortest_pull_up = length
            if length > longest_pull_up:
                longest_pull_up = length

        # use the halfway to determine whether the period it is long or short
        halfway = shortest_pull_up + (longest_pull_up - shortest_pull_up) / 2
        bits = []

        for i in range(0, len(pull_up_lengths)):
            bit = False
            if pull_up_lengths[i] > halfway:
                bit = True
            bits.append(bit)

        return bits

    def __bits_to_bytes(self, bits):
        the_bytes = []
        byte = 0

        for i in range(0, len(bits)):
            byte = byte << 1
            if (bits[i]):
                byte = byte | 1
            else:
                byte = byte | 0
            if ((i + 1) % 8 == 0):
                the_bytes.append(byte)
                byte = 0

        return the_bytes

    def __calculate_checksum(self, the_bytes):
        return the_bytes[0] + the_bytes[1] + the_bytes[2] + the_bytes[3] & 255

 

_______________________________________________________
- Con la librería de Adafruit.

- Instalamos la librería para el sensor DHT11.

- Instalamos git, se utiliza para bajar librerías.

# apt-get update

# apt-get install git-core

# git clone https://github.com/adafruit/Adafruit_Python_DHT.git

# cd Adafruit_Python_DHT

[Observaremos los archivos: dht_consola.py  dht_log.py  README.md]

# apt-get install build-essential python-dev

# sudo python setup.py install

---------------------------------

- Otra forma de instalar la librería de Adafruit

- Bajamos: Adafruit_Python_DHT-master.zip

- Luego: sudo python setup.py install

- https://www.electronicwings.com/raspberry-pi/dht11-interfacing-with-raspberry-pi

- Gráficos

https://d3js.org/

---------------------------------

- Otra manera si tenemos instalado pip

https://github.com/adafruit/Adafruit_Python_DHT

- sudo pip3 install Adafruit_DHT

pub_sub.py


# Juan Antonio Villalpando
# kio4.com


import RPi.GPIO as GPIO
from time import sleep # Función sleep del módulo time
import Adafruit_DHT
from random import randint # Función aleatorio


# LCD
import I2C_LCD_driver
mylcd = I2C_LCD_driver.lcd()


    # Publicación de Temperatura
    #humidity, temperature = Adafruit_DHT.read_retry(11, 4)
    temperature = randint(28,31)

 

___________________________________________________

 

- Mi correo:
juana1991@yahoo.com
- KIO4.COM - Política de cookies. Textos e imágenes propiedad del autor:
© Juan A. Villalpando
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