Python Raspberry PI - 在 LCD 上显示 USB 串行数据

Question

我有一个问题 在我的 RPi 上使用 4x16 LCD 显示器。我连接了显示器并用this tutorial进行了测试

现在我想通过 USB 从我的 arduino 接收数据。 This easy Tutorial Here 教我怎么做

我的问题：如何在显示器上显示数据？它应该更新所有的时间。 我尝试了一段时间 1: 循环，但出现多个错误。

有人可以帮助我吗？有没有更简单的方法？还是图书馆之类的东西？

谢谢

到目前为止我的代码（几乎所有内容都来自 LCD 教程）：

    #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()

在这段代码中，我没有使用任何 while 循环。有了这个解决方案，它就可以工作了。但我希望我的 arduino 中的数据应该一直在显示器上更新。

Answer 1

为什么不能使用 while 循环？ I. 总是放一个while True: 来包裹我的主循环程序。然后，如果需要，我会插入延迟。在这种情况下，我建议使用 pyserial (http://pyserial.sourceforge.net/) 与 Arduino 通信（通过 USB）。

也许你应该把这部分放在一个while循环中：

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)