11. Chapter LCD1602

In this chapter, we will learn about the LCD1602 Display Screen

11.1. Project I2C LCD1602

There are LCD1602 display screen and the I2C LCD. We will introduce both of them in this chapter. But what we use in this project is an I2C LCD1602 display screen. The LCD1602 Display Screen can display 2 lines of characters in 16 columns. It is capable of displaying numbers, letters, symbols, ASCII code and so on. As shown below is a monochrome LCD1602 Display Screen along with its circuit pin diagram

I2C LCD1602 Display Screen integrates a I2C interface, which connects the serial-input & parallel-output module to the LCD1602 Display Screen. This allows us to only use 4 lines to operate the LCD1602.

The serial-to-parallel IC chip used in this module is PCF8574T (PCF8574AT), and its default I2C address is 0x27(0x3F). You can also view the RPI bus on your I2C device address through command “i2cdetect -y 1” (refer to the “configuration I2C” section below).

Below is the PCF8574 chip pin diagram and its module pin diagram:

PCF8574 module pins and LCD1602 pins correspond to each other and connected to each other:

Because of this, as stated earlier, we only need 4 pins to control the16 pins of the LCD1602 Display Screen through the I2C interface.

In this project, we will use the I2C LCD1602 to display some static characters and dynamic variables.

11.1.1. Component List

Raspberry Pi (with 40 GPIO) x1 GPIO Extension Board & Ribbon Cable x1 Breadboard x1	Jumper Wires x4
I2C LCD1602 Module x1

11.1.2. Circuit

Note that the power supply for I2C LCD1602 in this circuit is 5V.

Schematic diagram

Hardware connection. If you need any support,please feel free to contact us via: support@freenove.com

Note

It is necessary to configure 12C and install Smbus first (see Chapter 7 for details)

11.1.3. Code

This code will have your RPi’s CPU temperature and System Time Displayed on the LCD1602.

11.1.3.1. Python Code I2CLCD1602

If you did not configure I2C and install Smbus, please refer to Chapter 7. If you did, continue.

First, observe the project result, and then learn about the code in detail.

Hint

If you have any concerns, please contact us via: support@freenove.com

1. Use cd command to enter 11.1.1_I2CLCD1602 directory of Python code.

$ cd ~/Freenove_Kit/Code/Python_GPIOZero_Code/11.1.1_I2CLCD1602

2. Use Python command to execute Python code I2CLCD1602.py.

$ python I2CLCD1602.py

After the program is executed, the LCD1602 Screen will display your RPi’s CPU Temperature and System Time.

So far, at this writing, we have two types of LCD1602 on sale. One needs to adjust the backlight, and the other does not.

The LCD1602 that does not need to adjust the backlight is shown in the figure below.

The following is the program code:

#!/usr/bin/env python3
########################################################################
# Filename    : I2CLCD1602.py
# Description : Use the LCD display data
# Author      : freenove
# modification: 2023/05/15
########################################################################
import smbus
from time import sleep, strftime
from datetime import datetime
from LCD1602 import CharLCD1602

lcd1602 = CharLCD1602()    
def get_cpu_temp():     # get CPU temperature from file "/sys/class/thermal/thermal_zone0/temp"
    tmp = open('/sys/class/thermal/thermal_zone0/temp')
    cpu = tmp.read()
    tmp.close()
    return '{:.2f}'.format( float(cpu)/1000 ) + ' C '

def get_time_now():     # get system time
    return datetime.now().strftime('    %H:%M:%S')

def loop():
    lcd1602.init_lcd()
    count = 0
    while(True):
        lcd1602.clear()
        lcd1602.write(0, 0, 'CPU: ' + get_cpu_temp() )# display CPU temperature
        lcd1602.write(0, 1, get_time_now() )   # display the time
        sleep(1)
def destroy():
    lcd1602.clear()
if __name__ == '__main__':
    print ('Program is starting ... ')
    try:
        loop()
    except KeyboardInterrupt:
        destroy()

In a while loop, set the cursor position, and display the CPU temperature and time.

while(True):
    lcd1602.clear()
    lcd1602.write(0, 0, 'CPU: ' + get_cpu_temp() )# display CPU temperature
    lcd1602.write(0, 1, get_time_now() )   # display the time
    sleep(1)

CPU temperature is stored in file “/sys/class/thermal/thermal_zone0/temp”. Open the file and read content of the file, and then convert it to Celsius degrees and return. Subfunction used to get CPU temperature is shown below:

def get_cpu_temp():     # get CPU temperature from file "/sys/class/thermal/thermal_zone0/temp"
    tmp = open('/sys/class/thermal/thermal_zone0/temp')
    cpu = tmp.read()
    tmp.close()
    return '{:.2f}'.format( float(cpu)/1000 ) + ' C '

Subfunction used to get time:

def get_time_now():     # get system time
    return datetime.now().strftime('    %H:%M:%S')

Details about LCD1602.py:

Module LCD1602

This module provides the basic operation method of LCD1602, including class CharLCD1602.

Some member functions are described as follows:

def init_lcd(self,addr=None, bl=1) : LDC1602 initializes the setting. When the addr is None, the I2C address of the device will be automatically scanned. You can also specify the I2C address, bl=1 to enable the backlight setting.

def clear(self) : clear the screen

def send_command(self,comm) : set the cursor position

def i2c_scan(self) : scan the device I2C address

def write(self,x, y, str) : display contents

Note

More information can be viewed through opening LCD1602.py.