Python Raspberry PI - Display USB Serial Data on LCD

Question

i have a question Using a 4x16 LCD display with my RPi. I connected The display and Tested it with this tutorial

Now i want to receive Data from my arduino over USB. This easy Tutorial Here showed me how to do it

My question: how can i get The Data on my display ? It should update all The Time. I tried a while 1: loop, but i get multiple error.

Can someone help me? Is there much easier way? Or Something like a Libary?

Thanks

My code so far (almost everything from the LCD Tutorial):

    #import
import RPi.GPIO as GPIO
import time
import serial

ser = serial.Serial('/dev/ttyACM0', 9600)

# 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 = 20    # Maximum characters per line
LCD_CHR = True
LCD_CMD = False

LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line
LCD_LINE_3 = 0x94 # LCD RAM address for the 3rd line
LCD_LINE_4 = 0xD4 # LCD RAM address for the 4th line 

# Timing constants
E_PULSE = 0.00005
E_DELAY = 0.00005

def main():
  # Main program block

  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
  lcd_init()

  # Toggle backlight off-on
  GPIO.output(LED_ON, False)
  time.sleep(1)
  GPIO.output(LED_ON, True)
  time.sleep(1)

  # Send some centred test
  lcd_byte(LCD_LINE_1, LCD_CMD)
  lcd_string("--------------------",2) 
  lcd_byte(LCD_LINE_2, LCD_CMD)
  lcd_string("Rasbperry Pi",2)
  lcd_byte(LCD_LINE_3, LCD_CMD)
  lcd_string("Model B",2)
  lcd_byte(LCD_LINE_4, LCD_CMD)
  lcd_string("--------------------",2)    

  time.sleep(3) # 3 second delay 

  string = ser.readline()         // Here i added the code for the Serial connection
  lcd_byte(LCD_LINE_1, LCD_CMD)
  lcd_string(string,3)          // lcd should display 'string'
  lcd_byte(LCD_LINE_2, LCD_CMD)
  lcd_string(".co.uk",3)  
  lcd_byte(LCD_LINE_3, LCD_CMD)
  lcd_string("",2) 
  lcd_byte(LCD_LINE_4, LCD_CMD)
  lcd_string("20x4 LCD Module Test",2)   

  time.sleep(20) # 20 second delay 

  # Blank display
  lcd_byte(LCD_LINE_1, LCD_CMD)
  lcd_string("",3)
  lcd_byte(LCD_LINE_2, LCD_CMD)
  lcd_string("",3)  
  lcd_byte(LCD_LINE_3, LCD_CMD)
  lcd_string("",2) 
  lcd_byte(LCD_LINE_4, LCD_CMD)
  lcd_string("",2)    

  time.sleep(3) # 3 second delay  

  # Turn off backlight
  GPIO.output(LED_ON, False)

def lcd_init():
  # Initialise display
  lcd_byte(0x33,LCD_CMD)
  lcd_byte(0x32,LCD_CMD)
  lcd_byte(0x28,LCD_CMD)
  lcd_byte(0x0C,LCD_CMD)  
  lcd_byte(0x06,LCD_CMD)
  lcd_byte(0x01,LCD_CMD)  

def lcd_string(message,style):
  # Send string to display
  # style=1 Left justified
  # style=2 Centred
  # style=3 Right justified

  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):
    lcd_byte(ord(message[i]),LCD_CHR)

def lcd_byte(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)   

if __name__ == '__main__':
  main()

In this code i didn't use any while loops. And with this solution it works. But i want that the data from my arduino should update all the time on the display.

Answer 1

Why can't you use while loops? I. Always put a while True: to encase my main looping program. Then I insert delays if needed. I would recommend pyserial ( http://pyserial.sourceforge.net/ ) to communicate with the Arduino in this case (over USB).

Maybe you should put this part in a while loop:

time.sleep(3) # 3 second delay 

string = ser.readline()         // Here i added the code for the Serial connection
lcd_byte(LCD_LINE_1, LCD_CMD)
lcd_string(string,3)          // lcd should display 'string'
lcd_byte(LCD_LINE_2, LCD_CMD)
lcd_string(".co.uk",3)  
lcd_byte(LCD_LINE_3, LCD_CMD)
lcd_string("",2) 
lcd_byte(LCD_LINE_4, LCD_CMD)
lcd_string("20x4 LCD Module Test",2)