Raspberry Pi 5使用smbus2控制LCD1602故障排查求助

初始代码 #

try:
    import smbus2
    LCD = smbus2.SMBus(1)
    address = 0x27
    IR = 0
    DR = 1
    ASCII_WORD = "HELLO"

    LCD.write_byte_data(address, IR, 0x80, force=None) #set the cursor at the beginning of line 1

    for char in ASCII_WORD:
        LCD.write_byte_data(address, IR, 0x10, force=None) #set the cursor 1 column left
        for bit in range(8):
            LCD.write_byte_data(address, DR, ord(char) >> (7 - bit), force=None)#write ASCII character
except KeyboardInterrupt:
    LCD.write_byte_data(address, IR, 0x01, force=None)#clear display
    LCD.close()

注：数据位取值参考16x2 LCD引脚图资料

代码逻辑 #

• 设置光标位置
• 写入目标字符的ASCII值

初始问题 #

运行代码后出现异常：光标位于第二行第5列，第一行第二列显示≣符号。推测for bit in range(8):循环多余，因为smbus2库会自动将十进制值转二进制逐位发送（若理解有误请指正），该循环可能导致ASCII码重复发送。

第一次调试后代码 #

try:
    import time
    import smbus2
    LCD = smbus2.SMBus(1)
    address = 0x27
    IR = 0
    DR = 1
    ASCII_WORD = "HELLO"

    LCD.write_byte_data(address, IR, 0x80, force=None) #set the cursor at the beginning of line 1
    for char in ASCII_WORD:
        LCD.write_byte_data(address, IR, 0x10, force=None) #set the cursor 1 column left
            LCD.write_byte_data(address, DR, ord(char) >> (7 - bit), force=None)#write ASCII character
except KeyboardInterrupt:
    LCD.write_byte_data(address, IR, 0x01, force=None)#clear display
    LCD.close()

注：代码存在缩进错误，内部write语句未正确对齐

新问题 #

运行此代码后，LCD背光完全熄灭（电源LED仍保持亮起）。

调试过程 #

• 移除except块，背光仍熄灭；
• 单独执行每条LCD.write_byte_data()语句，发现每条都会导致背光熄灭；
• 发现代码保留了>> (7 - bit)，移除后修改代码如下：

第二次修改后代码 #

try:
    import time
    import smbus2
    LCD = smbus2.SMBus(1)
    address = 0x27
    IR = 0
    DR = 1
    ASCII_WORD = "HELLO"

    LCD.write_byte_data(address, IR, 0x80, force=None) #set the cursor at the beginning of line 1
    for char in ASCII_WORD:
        LCD.write_byte_data(address, IR, 0x10, force=None) #set the cursor 1 column left
            LCD.write_byte_data(address, DR, ord(char), force=None)#write ASCII character
except KeyboardInterrupt:
    LCD.write_byte_data(address, IR, 0x01, force=None)#clear display
    LCD.close()

注：代码仍存在缩进错误

最新问题 #

• 运行此代码后，LCD屏幕保持开机时的蓝色背景无任何变化；
• 重新运行最初的代码，结果变为直接熄灭屏幕，而非之前的异常显示。

恳请帮忙排查这些问题，尤其是LCD为何会熄灭或无任何变化，非常感谢！

内容的提问来源于stack exchange，提问作者Matthew Moller