Question

尝试连接RFID以将输出提供给LCD屏幕时，出现错误。我该如何工作？

我注意到，当删除的reader = SimpleMFRC522（）和id，text = reader.read（）时，此代码有效，但是当我这样做时，RFID不能正常工作，因为它无法读取卡。


#!/usr/bin/env python

import RPi.GPIO as GPIO
import time
from mfrc522 import SimpleMFRC522

reader = SimpleMFRC522()

id.text = reader.read()

# Define GPIO to LCD mapping
LCD_RS = 25
LCD_EN  = 24
LCD_D4 = 23
LCD_D5 = 17
LCD_D6 = 18
LCD_D7 = 22

# Define some device constants
LCD_WIDTH = 16    # 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

# Timing constants
EN_PULSE = 0.0005
EN_DELAY = 0.0005

def main():
  # Main program block

  GPIO.setwarnings(False)
  GPIO.setmode(GPIO.BCM)       # Use BCM GPIO numbers
  GPIO.setup(LCD_EN, 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


  # Initialise display
  lcd_init()

  while True:

    # Send some test
    lcd_string("Rasbperry Pi",LCD_LINE_1)
    lcd_string("16x2 LCD Test",LCD_LINE_2)

    time.sleep(3) # 3 second delay

    # Send some text
    lcd_string("1234567890123456",LCD_LINE_1)
    lcd_string("abcdefghijklmnop",LCD_LINE_2)

    time.sleep(3)

    lcd_string(id, LCD_LINE_1)
    lcd_string(text, LCD_LINE_2)
    time.sleep(3) 


def lcd_init():
  # Initialise display
  lcd_byte(0x33,LCD_CMD) # 110011 Initialise
  lcd_byte(0x32,LCD_CMD) # 110010 Initialise
  lcd_byte(0x06,LCD_CMD) # 000110 Cursor move direction
  lcd_byte(0x0C,LCD_CMD) # 001100 Display On,Cursor Off, Blink Off
  lcd_byte(0x28,LCD_CMD) # 101000 Data length, number of lines, font size
  lcd_byte(0x01,LCD_CMD) # 000001 Clear display
  time.sleep(EN_DELAY)

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
  lcd_toggle_enable()

  # 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
  lcd_toggle_enable()

def lcd_toggle_enable():
  # Toggle enable
  time.sleep(EN_DELAY)
  GPIO.output(LCD_EN, True)
  time.sleep(EN_PULSE)
  GPIO.output(LCD_EN, False)
  time.sleep(EN_DELAY)

def lcd_string(message,line):
  # Send string to display



  message = message.ljust(LCD_WIDTH," ")

  lcd_byte(line, LCD_CMD)

  for i in range(LCD_WIDTH):
    lcd_byte(ord(message[i]),LCD_CHR)

if __name__ == '__main__':

  try:
    main()
    id,text = reader.read()
    lcd_string(text)

  except KeyboardInterrupt:
    pass
  finally:
    lcd_byte(0x01, LCD_CMD)
    lcd_string("Goodbye!",LCD_LINE_1)
    time.sleep(3)
    lcd_string(" ",LCD_LINE_1)
    lcd_string(" ",LCD_LINE_2)
    GPIO.cleanup()

我希望我的卡的ID出现在LCD屏幕上，但出现一个我不理解的错误消息


Traceback (most recent call last):
  File "lcd_16x2.py", line 203, in <module>
    lcd_byte(0x01, LCD_CMD)
  File "lcd_16x2.py", line 137, in lcd_byte
    GPIO.output(LCD_RS, mode) # RS
ValueError: The channel sent is invalid on a Raspberry Pi

尝试将RFID与LCD屏幕和Raspberry Pi连接时出错

0 个答案: