Whenever you come across a LCD that looks like it has 16 connectors it is most likely using a HD44780 controller. These devices provide the same pinouts making them relatively easy to work with. The LCD uses a parallel interface meaning that we will need many pins from our raspberry pi to control it. In this tutorial we will use 4 data pins (4-bit mode) and two control pins.The data pins are straight forward. They are sending data to the display (toggled high/low). We will only be using write mode and not reading any data.

The register select pin has two uses. When pulled low it can send commands to the LCD (like position to move to, or clear the screen). This is referred to as writing to the instruction or command register. When toggled the other way (1) the register select pin goes into a data mode and will be used to send data to the screen.

The read/write pin will be pulled low (write only) as we only want to write to the LCD based on this setup.

The enable pin will be toggled to write data to the registers.

LCD Pinout

1. Ground
2. VCC – 5v not 3.3v
3. Contrast adjustment (VO) from potentiometer
4. Register Select (RS). RS=0: Command, RS=1: Data
5. Read/Write (R/W). R/W=0: Write, R/W=1: Read (we won’t use this pin)
6. Clock (Enable). Falling edge triggered
7. Bit 0 (Not used in 4-bit operation)
8. Bit 1 (Not used in 4-bit operation)
9. Bit 2 (Not used in 4-bit operation)
10. Bit 3 (Not used in 4-bit operation)
11. Bit 4
12. Bit 5
13. Bit 6
14. Bit 7
15. Backlight LED Anode (+)
16. Backlight LED Cathode (-)

Before wiring, check that your LCD has an LED backlight, not an EL backlight. LED backlights use 10-40mA of power, EL backlights use 200+ma! EL backlights are often cheap to get but are not usable, make sure you don’t use one or you will overload the Pi. Some cheap LCDs that have LED backlights do not include a resistor on the LCD module for the backlight, if you’re not sure, connect a 1Kohm resistor between pin 15 and 5V instead of connecting directly. All Adafruit LCDs have LED backlights with built in resistors so you do not need an extra resistor!

Wiring Diagram

First, connect the cobber power pins to the breadboard power rail. +5.0V from the cobbler goes to the red striped rail (red wire) and GND from the cobbler goes to the blue striped rail (black wire)

In order to send data to the LCD we are going to wire  it up as follows

• Pin #1 of the LCD goes to ground (black wire)
• Pin #2 of the LCD goes to +5V (red wire)
• Pin #3 (Vo) connects to the middle of the potentiometer (orange wire)
• Pin #4 (RS) connects to the Cobber #25 (yellow wire)
• Pin #5 (RW) goes to ground (black wire)
• Pin #6 (EN) connects to cobber #24 (green wire)
• Skip LCD Pins #7, #8, #9 and #10
• Pin #11 (D4) connects to cobber #23 (blue wire)
• Pin #12 (D5) connects to cobber #17 (violet wire)
• Pin #13 (D6) connects to cobber #21 (gray wire)
• Pin #14 (D7) connects to cobber #22 (white wire)
• Pin #15 (LED +) goes to +5V (red wire)
• Pin #16 (LED -) goes to ground (black wire)

Then connect up the potentiometer, the left pin connects to ground (black wire) and the right pin connects to +5V (red wire)

Schematic

Necessary Packages

This guide is based on Debian’s “Wheezy” release for Raspberry Pi. It was made available in Mid July 2012. The following items must be installed in order to utilize the Raspberry Pi’s GPIO pins. If you are running Adafruit’s Occidentalis you can just skip this page.

Add the latest dev packages for Python (2.x)

Python Script

The Code

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# SPDX-FileCopyrightText: 2018 Mikey Sklar for Adafruit Industries
#
# SPDX-License-Identifier: MIT

from subprocess import Popen, PIPE
from time import sleep
from datetime import datetime
import board
import digitalio
import adafruit_character_lcd.character_lcd as characterlcd

# Modify this if you have a different sized character LCD
lcd_columns = 16
lcd_rows = 2

# compatible with all versions of RPI as of Jan. 2019
# v1 - v3B+
lcd_rs = digitalio.DigitalInOut(board.D22)
lcd_en = digitalio.DigitalInOut(board.D17)
lcd_d4 = digitalio.DigitalInOut(board.D25)
lcd_d5 = digitalio.DigitalInOut(board.D24)
lcd_d6 = digitalio.DigitalInOut(board.D23)
lcd_d7 = digitalio.DigitalInOut(board.D18)


# Initialise the lcd class
lcd = characterlcd.Character_LCD_Mono(lcd_rs, lcd_en, lcd_d4, lcd_d5, lcd_d6,
                                      lcd_d7, lcd_columns, lcd_rows)

# looking for an active Ethernet or WiFi device
def find_interface():
    find_device = "ip addr show"
    interface_parse = run_cmd(find_device)
    for line in interface_parse.splitlines():
        if "state UP" in line:
            dev_name = line.split(':')[1]
    return dev_name

# find an active IP on the first LIVE network device
def parse_ip():
    find_ip = "ip addr show %s" % interface
    find_ip = "ip addr show %s" % interface
    ip_parse = run_cmd(find_ip)
    for line in ip_parse.splitlines():
        if "inet " in line:
            ip = line.split(' ')[5]
            ip = ip.split('/')[0]
    return ip

# run unix shell command, return as ASCII
def run_cmd(cmd):
    p = Popen(cmd, shell=True, stdout=PIPE)
    output = p.communicate()[0]
    return output.decode('ascii')

# wipe LCD screen before we start
lcd.clear()

# before we start the main loop - detect active network device and ip address
sleep(2)
interface = find_interface()
ip_address = parse_ip()

while True:

    # date and time
    lcd_line_1 = datetime.now().strftime('%b %d  %H:%M:%S\n')

    # current ip address
    lcd_line_2 = "IP " + ip_address

    # combine both lines into one update to the display
    lcd.message = lcd_line_1 + lcd_line_2

    sleep(2)

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Download the Code

Let’s put this file right in your home directory for simplicity. The wget command makes things easy.

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$ wget https://raw.githubusercontent.com/adafruit/Adafruit_Learning_System_Guides/master/Drive_a_16x2_LCD_with_the_Raspberry_Pi/Drive_a_16x2_LCD_with_the_Raspberry_Pi.py

Running the Code

The following command will start the program and you should see the LCD display come to life with date, time and IP address.

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$ sudo python3 ./Drive_a_16x2_LCD_with_the_Raspberry_Pi.py

Display Time & IP on Every Boot

It’s all fine and dandy to have a script which we can manually run, but wouldn’t it be nice to have the time and ip address pop up on the display when the Raspberry Pi boots up? This is done using an init script which runs our Python code every time your Raspberry Pi boots up.

Download the service file

The following command will allow you to download the lcd.service file directly to your Pi.

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$ wget https://raw.githubusercontent.com/adafruit/Adafruit_Learning_System_Guides/master/Drive_a_16x2_LCD_with_the_Raspberry_Pi/lcd.service

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[Unit]
Description=LCD date|time|ip
Requires=network-online.target
After=network-online.target

[Service]
ExecStart=/usr/bin/python3 Drive_a_16x2_LCD_with_the_Raspberry_Pi.py
WorkingDirectory=/home/pi
StandardOutput=inherit
StandardError=inherit
Restart=always
User=pi

[Install]
WantedBy=network-online.target

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Place the lcd.service file

The lcd.service file needs to be copied into the correct location and the systemctl command can be used to start | stop | enable the service. It is a good idea to test this before enabling as there might be a minor path difference on your system.

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$ sudo cp lcd.service /etc/systemd/system

Test the lcd.service

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$ sudo systemctl daemon-reload
$ sudo systemctl start lcd.service
$ ps auxww | grep -i 16x2

The following commands read the updates to the service file, start the lcd.service and confirm that the process is running. If the script shows up in the ‘ps’ command output you have done everything correctly and can now enable the service and reboot. The service should activate upon bootup automatically.

Enable lcd.service

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$ sudo systemctl enable lcd.service

Now on each boot the LCD will automatically show the date/time/ip address on startup. This means you will know when the Pi is reachable and what the ip address is without having to plug a monitor in.

Time Zone

Last, but not least: My Pi came configured with UT (Universal Time). I prefer to see time based on my time zone, which is Mountain. Here is how to configure time on the Pi for any location. This is a one time configuration setting that will survive between reboots.

We can use raspi-config to easy set our timezone. Choose the following:

• Localisation Options
• Change Timezone
• Continent / Country
• Time zone

Run raspi-config

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$ sudo raspi-config