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在树莓派4B上使用LCD1602液晶屏

 2 years ago
source link: https://direct5dom.github.io/2021/10/31/%E5%9C%A8%E6%A0%91%E8%8E%93%E6%B4%BE4B%E4%B8%8A%E4%BD%BF%E7%94%A8LCD1602%E6%B6%B2%E6%99%B6%E5%B1%8F/
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raspberry-pi-logo-1920.png

LCD1602技术原理

LCD1602.png

LCD1602可以显示16 x 2个字符，且只支持标准ASCII码字符和日文希腊文字符。

LCD1602一共有16个针脚，如果直接将其连接在树莓派上的话非常占用资源，所以我这里用的是和 I2C（I2C）模块集成在一起的板子。I2C 只有四个针脚，这样就可以大幅度节约树莓派针脚去干其他事，I2C接口引脚如下：

引脚 功能
GND 接地
VCC 控制电压
SDA I2C数据
SCL I2C时钟

LCD1602连接树莓派GPIO.png

安装i2c-tools

使用命令：

sudo apt install i2c-tools

安装python-smbus

使用命令：

sudo apt install python-smbus

查看I2C设备地址

使用命令及返回：

$ sudo i2cdetect -y 1 
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- 27 -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

看到地址为0x27。这说明已经成功连接了1602A 。接下来就可以控制1602A显示信息了。

代码来自：树莓派通过 I2C 驱动 LCD1602 液晶屏 | 树莓派实验室 (nxez.com)

驱动程序LCD1602.py：

import time
import smbus
BUS = smbus.SMBus(1)
LCD_ADDR = 0x27
BLEN = 1 #turn on/off background light

def turn_light(key):
    global BLEN
    BLEN = key
    if key ==1 :
        BUS.write_byte(LCD_ADDR ,0x08)
    else:
        BUS.write_byte(LCD_ADDR ,0x00)

def write_word(addr, data):
    global BLEN
    temp = data
    if BLEN == 1:
        temp |= 0x08
    else:
        temp &= 0xF7
    BUS.write_byte(addr ,temp)

def send_command(comm):
    # Send bit7-4 firstly
    buf = comm & 0xF0
    buf |= 0x04               # RS = 0, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

# Send bit3-0 secondly
    buf = (comm & 0x0F) << 4
    buf |= 0x04               # RS = 0, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

def send_data(data):
    # Send bit7-4 firstly
    buf = data & 0xF0
    buf |= 0x05               # RS = 1, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

# Send bit3-0 secondly
    buf = (data & 0x0F) << 4
    buf |= 0x05               # RS = 1, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

def init_lcd():
    try:
        send_command(0x33) # Must initialize to 8-line mode at first
        time.sleep(0.005)
        send_command(0x32) # Then initialize to 4-line mode
        time.sleep(0.005)
        send_command(0x28) # 2 Lines & 5*7 dots
        time.sleep(0.005)
        send_command(0x0C) # Enable display without cursor
        time.sleep(0.005)
        send_command(0x01) # Clear Screen
        BUS.write_byte(LCD_ADDR ,0x08)
    except:
        return False
    else:
        return True

def clear_lcd():
    send_command(0x01) # Clear Screen

def print_lcd(x, y, str):
    if x < 0:
        x = 0
    if x > 15:
        x = 15
    if y <0:
        y = 0
    if y > 1:
        y = 1

# Move cursor
    addr = 0x80 + 0x40 * y + x
    send_command(addr)

for chr in str:
        send_data(ord(chr))

if __name__ == '__main__':
    init_lcd()
    print_lcd(0, 0, 'Hello, world!')

显示时间的示例程序time.py：

#!/user/bin/env python 
import smbus
import time
import sys
import LCD1602 as LCD

if __name__ == '__main__':  
    LCD.init_lcd()
    time.sleep(1)
    LCD.print_lcd(2, 0, 'WWW.QUWJ.COM')
    for x in range(1, 4):
        LCD.turn_light(0)
        LCD.print_lcd(4, 1, 'LIGHT OFF')
        time.sleep(0.5)
        LCD.turn_light(1)
        LCD.print_lcd(4, 1, 'LIGHT ON ')
        time.sleep(0.5)

LCD.turn_light(1)

while True:
        now = time.strftime('%m/%d %H:%M:%S', time.localtime(time.time()))
        LCD.print_lcd(1, 1, now)
        time.sleep(0.2)

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