物联网开发笔记（25）- 使用Micropython开发ESP32开发板之控制LCD1602显示屏

这一节我们讲解了如何控制LCD1602显示屏，显示两行字。

一、目的

使用MicroPython开发ESP32开发板控制LCD1602显示屏

二、环境

ESP32 + LCD1602显示屏 + Thonny IDE + 面包板（非必须）+ 几根杜邦线（为了方便讲解，这里使用Wokwi仿真）

I2C配置的有下图的黑色小板（小班上蓝色的为调节LCD亮度的旋钮，旁边是PCF8574T芯片，相当于是开发板和LCD显示屏的桥梁作用）：

标准配置的如下图：

接线图：

注意需要使用开发板上的5V电压，而不是3.3V。真实环境下使用3.3V会无法显示或者显示很暗。

三、LCD1602显示屏介绍

请查看官方文档：

wokwi-lcd1602 Reference | Wokwi DocsAn LCD with 2 lines, 16 characters per line.https://docs.wokwi.com/parts/wokwi-lcd1602 LCD1602显示屏有两种：一种是I2C的（4个针脚），两一种是标准的（16个针脚）。

I2C配置模拟控制LCD模块的PCF8574T芯片。

I2C配置（4个针脚）：

标准配置（16个针脚）：

四、下面举个例子给大家演示一下LCD1602显示屏的使用方法

先给大家讲解一下怎么获得1602LCD的地址：我们打开官方网站，查看：

Quick reference for the ESP32 — MicroPython 1.19.1 documentationhttp://docs.micropython.org/en/latest/esp32/quickref.html#software-i2c-bus

使用以上代码就可以打印出1602lcd显示屏的地址。

from machine import Pin, SoftI2Ci2c = SoftI2C(sda=Pin(15), scl=Pin(2), freq=100000)lcdAddr = i2c.scan() # scan for devices
print(lcdAddr)  # 打印出lcd的地址

从上图可以看到地址是39。

上代码：

main.py

import time
from machine import SoftI2C, Pin
from esp32_i2c_1602lcd import I2cLcdDEFAULT_I2C_ADDR = 0x27  # lcd1602的地址是0x27
i2c = SoftI2C(sda=Pin(15),scl=Pin(2),freq=100000)  # 定义一个SoftI2C的对象，指定sda和scl的GPIO口，并设置好通信的频率
lcd = I2cLcd(i2c, DEFAULT_I2C_ADDR, 2, 16)  # 定义一个I2CLcd对象，设置模式为i2c，地址，行数，行的大小16个字节for i in range(1, 10):lcd.clear()  # 清屏lcd.putstr("...{}...\n".format(i))  # 显示第一行数据，\n为换行符lcd.putstr("I love Shanghai")   # 显示第二行数据time.sleep(1)

diagram.json

{"version": 1,"author": "Anonymous maker","editor": "wokwi","parts": [{"type": "wokwi-esp32-devkit-v1","id": "esp","top": -12,"left": -168.66,"attrs": { "env": "micropython-20220618-v1.19.1" }},{"type": "wokwi-lcd1602","id": "lcd1","top": 3.77,"left": -4.5,"attrs": { "pins": "i2c", "background": "blue", "color": "white" }}],"connections": [[ "esp:TX0", "$serialMonitor:RX", "", [] ],[ "esp:RX0", "$serialMonitor:TX", "", [] ],[ "lcd1:GND", "esp:GND.1", "black", [ "h-30.66", "v101.73" ] ],[ "esp:D2", "lcd1:SCL", "green", [ "h22.86", "v-50.9" ] ],[ "lcd1:SDA", "esp:D15", "cyan", [ "h-11.33", "v65.4" ] ],[ "lcd1:VCC", "esp:VIN", "red", [ "h-20.38", "v152.84", "h-162.43", "v-55.67" ] ]]
}

lcd_api.py

"""Provides an API for talking to HD44780 compatible character LCDs."""import timeclass LcdApi:"""Implements the API for talking with HD44780 compatible character LCDs.This class only knows what commands to send to the LCD, and not how to getthem to the LCD.It is expected that a derived class will implement the hal_xxx functions."""# The following constant names were lifted from the avrlib lcd.h# header file, however, I changed the definitions from bit numbers# to bit masks.## HD44780 LCD controller command setLCD_CLR = 0x01              # DB0: clear displayLCD_HOME = 0x02             # DB1: return to home positionLCD_ENTRY_MODE = 0x04       # DB2: set entry modeLCD_ENTRY_INC = 0x02        # --DB1: incrementLCD_ENTRY_SHIFT = 0x01      # --DB0: shiftLCD_ON_CTRL = 0x08          # DB3: turn lcd/cursor onLCD_ON_DISPLAY = 0x04       # --DB2: turn display onLCD_ON_CURSOR = 0x02        # --DB1: turn cursor onLCD_ON_BLINK = 0x01         # --DB0: blinking cursorLCD_MOVE = 0x10             # DB4: move cursor/displayLCD_MOVE_DISP = 0x08        # --DB3: move display (0-> move cursor)LCD_MOVE_RIGHT = 0x04       # --DB2: move right (0-> left)LCD_FUNCTION = 0x20         # DB5: function setLCD_FUNCTION_8BIT = 0x10    # --DB4: set 8BIT mode (0->4BIT mode)LCD_FUNCTION_2LINES = 0x08  # --DB3: two lines (0->one line)LCD_FUNCTION_10DOTS = 0x04  # --DB2: 5x10 font (0->5x7 font)LCD_FUNCTION_RESET = 0x30   # See "Initializing by Instruction" sectionLCD_CGRAM = 0x40            # DB6: set CG RAM addressLCD_DDRAM = 0x80            # DB7: set DD RAM addressLCD_RS_CMD = 0LCD_RS_DATA = 1LCD_RW_WRITE = 0LCD_RW_READ = 1def __init__(self, num_lines, num_columns):self.num_lines = num_linesif self.num_lines > 4:self.num_lines = 4self.num_columns = num_columnsif self.num_columns > 40:self.num_columns = 40self.cursor_x = 0self.cursor_y = 0self.backlight = Trueself.display_off()self.backlight_on()self.clear()self.hal_write_command(self.LCD_ENTRY_MODE | self.LCD_ENTRY_INC)self.hide_cursor()self.display_on()def clear(self):"""Clears the LCD display and moves the cursor to the top leftcorner."""self.hal_write_command(self.LCD_CLR)self.hal_write_command(self.LCD_HOME)self.cursor_x = 0self.cursor_y = 0def show_cursor(self):"""Causes the cursor to be made visible."""self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY |self.LCD_ON_CURSOR)def hide_cursor(self):"""Causes the cursor to be hidden."""self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY)def blink_cursor_on(self):"""Turns on the cursor, and makes it blink."""self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY |self.LCD_ON_CURSOR | self.LCD_ON_BLINK)def blink_cursor_off(self):"""Turns on the cursor, and makes it no blink (i.e. be solid)."""self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY |self.LCD_ON_CURSOR)def display_on(self):"""Turns on (i.e. unblanks) the LCD."""self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY)def display_off(self):"""Turns off (i.e. blanks) the LCD."""self.hal_write_command(self.LCD_ON_CTRL)def backlight_on(self):"""Turns the backlight on.This isn't really an LCD command, but some modules have backlightcontrols, so this allows the hal to pass through the command."""self.backlight = Trueself.hal_backlight_on()def backlight_off(self):"""Turns the backlight off.This isn't really an LCD command, but some modules have backlightcontrols, so this allows the hal to pass through the command."""self.backlight = Falseself.hal_backlight_off()def move_to(self, cursor_x, cursor_y):"""Moves the cursor position to the indicated position. The cursorposition is zero based (i.e. cursor_x == 0 indicates first column)."""self.cursor_x = cursor_xself.cursor_y = cursor_yaddr = cursor_x & 0x3fif cursor_y & 1:addr += 0x40    # Lines 1 & 3 add 0x40if cursor_y & 2:addr += 0x14    # Lines 2 & 3 add 0x14self.hal_write_command(self.LCD_DDRAM | addr)def putchar(self, char):"""Writes the indicated character to the LCD at the current cursorposition, and advances the cursor by one position."""if char != '\n':self.hal_write_data(ord(char))self.cursor_x += 1if self.cursor_x >= self.num_columns or char == '\n':self.cursor_x = 0self.cursor_y += 1if self.cursor_y >= self.num_lines:self.cursor_y = 0self.move_to(self.cursor_x, self.cursor_y)def putstr(self, string):"""Write the indicated string to the LCD at the current cursorposition and advances the cursor position appropriately."""for char in string:self.putchar(char)def custom_char(self, location, charmap):"""Write a character to one of the 8 CGRAM locations, availableas chr(0) through chr(7)."""location &= 0x7self.hal_write_command(self.LCD_CGRAM | (location << 3))time.sleep_us(40)for i in range(8):self.hal_write_data(charmap[i])time.sleep_us(40)self.move_to(self.cursor_x, self.cursor_y)def hal_backlight_on(self):"""Allows the hal layer to turn the backlight on.If desired, a derived HAL class will implement this function."""passdef hal_backlight_off(self):"""Allows the hal layer to turn the backlight off.If desired, a derived HAL class will implement this function."""passdef hal_write_command(self, cmd):"""Write a command to the LCD.It is expected that a derived HAL class will implement thisfunction."""raise NotImplementedErrordef hal_write_data(self, data):"""Write data to the LCD.It is expected that a derived HAL class will implement thisfunction."""raise NotImplementedError

esp32_i2c_lcd1602lcd.py

"""Implements a HD44780 character LCD connected via PCF8574 on I2C.This was tested with: https://www.wemos.cc/product/d1-mini.html"""from lcd_api import LcdApi
from machine import I2C
from time import sleep_ms# Defines shifts or masks for the various LCD line attached to the PCF8574MASK_RS = 0x01
MASK_RW = 0x02
MASK_E = 0x04
SHIFT_BACKLIGHT = 3
SHIFT_DATA = 4class I2cLcd(LcdApi):"""Implements a HD44780 character LCD connected via PCF8574 on I2C."""def __init__(self, i2c, i2c_addr, num_lines, num_columns):self.i2c = i2cself.i2c_addr = i2c_addrself.i2c.writeto(self.i2c_addr, bytearray([0]))sleep_ms(20)   # Allow LCD time to powerup# Send reset 3 timesself.hal_write_init_nibble(self.LCD_FUNCTION_RESET)sleep_ms(5)    # need to delay at least 4.1 msecself.hal_write_init_nibble(self.LCD_FUNCTION_RESET)sleep_ms(1)self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)sleep_ms(1)# Put LCD into 4 bit modeself.hal_write_init_nibble(self.LCD_FUNCTION)sleep_ms(1)LcdApi.__init__(self, num_lines, num_columns)cmd = self.LCD_FUNCTIONif num_lines > 1:cmd |= self.LCD_FUNCTION_2LINESself.hal_write_command(cmd)def hal_write_init_nibble(self, nibble):"""Writes an initialization nibble to the LCD.This particular function is only used during initialization."""byte = ((nibble >> 4) & 0x0f) << SHIFT_DATAself.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))self.i2c.writeto(self.i2c_addr, bytearray([byte]))def hal_backlight_on(self):"""Allows the hal layer to turn the backlight on."""self.i2c.writeto(self.i2c_addr, bytearray([1 << SHIFT_BACKLIGHT]))def hal_backlight_off(self):"""Allows the hal layer to turn the backlight off."""self.i2c.writeto(self.i2c_addr, bytearray([0]))def hal_write_command(self, cmd):"""Writes a command to the LCD.Data is latched on the falling edge of E."""byte = ((self.backlight << SHIFT_BACKLIGHT) | (((cmd >> 4) & 0x0f) << SHIFT_DATA))self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))self.i2c.writeto(self.i2c_addr, bytearray([byte]))byte = ((self.backlight << SHIFT_BACKLIGHT) | ((cmd & 0x0f) << SHIFT_DATA))self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))self.i2c.writeto(self.i2c_addr, bytearray([byte]))if cmd <= 3:# The home and clear commands require a worst case delay of 4.1 msecsleep_ms(5)def hal_write_data(self, data):"""Write data to the LCD."""byte = (MASK_RS | (self.backlight << SHIFT_BACKLIGHT) | (((data >> 4) & 0x0f) << SHIFT_DATA))self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))self.i2c.writeto(self.i2c_addr, bytearray([byte]))byte = (MASK_RS | (self.backlight << SHIFT_BACKLIGHT) | ((data & 0x0f) << SHIFT_DATA))self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))self.i2c.writeto(self.i2c_addr, bytearray([byte]))

五、演示效果，请参考如下链接：

Wokwi Arduino and ESP32 Simulatorhttps://wokwi.com/projects/345562142596923987

六、扩展

在实际产品开发中，开发的GPIO口等是十分珍贵的资源，我们常用i2c模式来进行开发，减少IO口的占用，同时布线也十分简单。

我在GitHub上找到LCD1602的驱动，其中包含其他开发板的LCD1602驱动，大家有空可以学习一下。

GitHub - dhylands/python_lcd: Python based library for talking to character based LCDs.

你也可以去Micropython论坛寻找有用的资料：

MicroPython Forum (Archive) - Searchhttps://forum.micropython.org/search.php?keywords=lcd1602&fid%5B0%5D=18

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物联网开发笔记（25）- 使用Micropython开发ESP32开发板之控制LCD1602显示屏

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