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lcd.py
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lcd.py
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#!/usr/bin/python
#
# HD44780 LCD Test Script for
# Raspberry Pi
#
# Author : Matt Hawkins
# Site : http://www.raspberrypi-spy.co.uk
#
# Date : 03/08/2012
#
# The wiring for the LCD is as follows:
# 1 : GND
# 2 : 5V
# 3 : Contrast (0-5V)*
# 4 : RS (Register Select)
# 5 : R/W (Read Write) - GROUND THIS PIN
# 6 : Enable or Strobe
# 7 : Data Bit 0 - NOT USED
# 8 : Data Bit 1 - NOT USED# 9 : Data Bit 2 - NOT USED
# 10: Data Bit 3 - NOT USED
# 11: Data Bit 4
# 12: Data Bit 5
# 13: Data Bit 6
# 14: Data Bit 7
# 15: LCD Backlight +5V**
# 16: LCD Backlight GND
# Code was modified to use it as a library
import time
try:
import RPi.GPIO as GPIO
except RuntimeError:
print('Not running on the pi, some features won\'t be available')
# Define GPIO to LCD mapping
LCD_RS = 7
LCD_E = 8
LCD_D4 = 25
LCD_D5 = 24
LCD_D6 = 23
LCD_D7 = 18
LED_ON = 15
# Define some device constants
LCD_WIDTH = 16 # Maximum characters per line
LCD_CHR = True
LCD_CMD = False
# LCD RAM address for the 2 lines
LCD_LINE_1 = 0x80
LCD_LINE_2 = 0xC0
# Timing constants
E_PULSE = 0.00005
E_DELAY = 0.00005
class LCD:
def __init__(self):
GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM) # Use BCM GPIO numbers
GPIO.setup(LCD_E, GPIO.OUT) # E
GPIO.setup(LCD_RS, GPIO.OUT) # RS
GPIO.setup(LCD_D4, GPIO.OUT) # DB4
GPIO.setup(LCD_D5, GPIO.OUT) # DB5
GPIO.setup(LCD_D6, GPIO.OUT) # DB6
GPIO.setup(LCD_D7, GPIO.OUT) # DB7
GPIO.setup(LED_ON, GPIO.OUT) # Backlight enable
# Initialise display
self._lcd_byte(0x33, LCD_CMD)
self._lcd_byte(0x32, LCD_CMD)
self._lcd_byte(0x28, LCD_CMD)
self._lcd_byte(0x0C, LCD_CMD)
self._lcd_byte(0x06, LCD_CMD)
self._lcd_byte(0x01, LCD_CMD)
self.blight(1)
def _clean_up(self):
GPIO.cleanup()
def _lcd_byte(self, bits, mode):
# Send byte to data pins
# bits = data
# mode = True for character
# False for command
GPIO.output(LCD_RS, mode) # RS
# High bits
GPIO.output(LCD_D4, False)
GPIO.output(LCD_D5, False)
GPIO.output(LCD_D6, False)
GPIO.output(LCD_D7, False)
if bits & 0x10 == 0x10:
GPIO.output(LCD_D4, True)
if bits & 0x20 == 0x20:
GPIO.output(LCD_D5, True)
if bits & 0x40 == 0x40:
GPIO.output(LCD_D6, True)
if bits & 0x80 == 0x80:
GPIO.output(LCD_D7, True)
# Toggle 'Enable' pin
time.sleep(E_DELAY)
GPIO.output(LCD_E, True)
time.sleep(E_PULSE)
GPIO.output(LCD_E, False)
time.sleep(E_DELAY)
# Low bits
GPIO.output(LCD_D4, False)
GPIO.output(LCD_D5, False)
GPIO.output(LCD_D6, False)
GPIO.output(LCD_D7, False)
if bits & 0x01 == 0x01:
GPIO.output(LCD_D4, True)
if bits & 0x02 == 0x02:
GPIO.output(LCD_D5, True)
if bits & 0x04 == 0x04:
GPIO.output(LCD_D6, True)
if bits & 0x08 == 0x08:
GPIO.output(LCD_D7, True)
# Toggle 'Enable' pin
time.sleep(E_DELAY)
GPIO.output(LCD_E, True)
time.sleep(E_PULSE)
GPIO.output(LCD_E, False)
time.sleep(E_DELAY)
def _displace(self, text):
# takes a 16 char string and formats it to show it in movement
if len(text) > 16:
print ('String cannot be longer than 16 characters')
return
ret = []
text = list(text)
for x in range(1, 16):
ret.append(text[x])
ret.append(text[0])
ret = ''.join(ret)
return ret
def _lcd_string(self, message, style):
# Send string to display
if style == 1:
message = message.ljust(LCD_WIDTH, " ")
elif style == 2:
message = message.center(LCD_WIDTH, " ")
elif style == 3:
message = message.rjust(LCD_WIDTH, " ")
for i in range(LCD_WIDTH):
self._lcd_byte(ord(message[i]), LCD_CHR)
def send_text(self, text, row=1, justification=2):
# ROW: send 'text' to row number 1 or 2
# Justification: left(1), center(2), (3)right
if (len(text) > 16):
print "Text not valid. Longer than 16 characters"
text = 'ERR:line too long'
rows = {
1: LCD_LINE_1,
2: LCD_LINE_2
}
self._lcd_byte(rows.get(row, 1), LCD_CMD)
self._lcd_string(text, justification)
def blight(self, state):
GPIO.output(LED_ON, state)
def move(self, seconds, text):
for x in range(seconds * 2):
self.send_text(text, 1)
time.sleep(0.5)
text = self._displace(text)