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LCD1602 Display

Display static text and a live-updating counter on an LCD1602 character display, controlled over I2C.

New Concepts

  • Character LCD displays

LCD1602

The LCD1602 displays 2 rows of 16 characters — letters, numbers, symbols, and ASCII text.

LCD1602 component LCD1602 pinout

Driven directly, the LCD1602 needs many pins. This kit's module adds a PCF8574 I2C-to-parallel backpack, converting those many parallel pins down to just SDA/SCL — its default address is 0x27 (or 0x3F on the PCF8574A variant).

I2C LCD1602 module pinout PCF8574 chip pinout

Component List

Components

Circuit

Wiring Diagram

Disconnect all power before building the circuit. Reconnect once verified.

Wiring Diagram

Connections:

  • LCD1602 SCL → GPIO13
  • LCD1602 SDA → GPIO14
  • LCD1602 VCC → 5V
  • LCD1602 GND → GND

Schematic Diagram

Schematic Diagram

Code

File: 04_output/code/IIC_LCD1602.py Modules: 04_output/code/I2C_LCD.py, 04_output/code/LCD_API.py

import time
from machine import I2C, Pin
from I2C_LCD import I2cLcd

i2c = I2C(scl=Pin(13), sda=Pin(14), freq=400000)
devices = i2c.scan()
if len(devices) == 0:
    print("No i2c device !")
else:
    for device in devices:
        print("I2C addr: "+hex(device))
        lcd = I2cLcd(i2c, device, 2, 16)

try:
    lcd.move_to(0, 0)
    lcd.putstr("Hello,world!")
    count = 0
    while True:
        lcd.move_to(0, 1)
        lcd.putstr("Counter:%d" %(count))
        time.sleep_ms(1000)
        count += 1
except:
    pass

How to Run

Online

  1. Open Thonny → 04_output/code/.
  2. Right-click I2C_LCD.py and LCD_API.py → Upload to / — wait for both to finish uploading.
  3. Double-click IIC_LCD1602.py.
  4. Click Run current script — "Hello,world!" appears on row 1, and a counter increments on row 2 once per second.

Code Explanation

Scan the I2C bus

i2c = I2C(scl=Pin(13), sda=Pin(14), freq=400000)
devices = i2c.scan()

scan() checks every possible address and returns a list of devices that respond — useful since the LCD's I2C address depends on which backpack chip variant it uses (0x27 vs 0x3F).

Create the LCD object

for device in devices:
    print("I2C addr: "+hex(device))
    lcd = I2cLcd(i2c, device, 2, 16)

Builds an I2cLcd for whichever address was found, configured for 2 rows × 16 columns.

Position the cursor and write text

lcd.move_to(0, 0)
lcd.putstr("Hello,world!")

move_to(column, row) positions the cursor (0-indexed); putstr() then writes a string starting there.

Update one line repeatedly

while True:
    lcd.move_to(0, 1)
    lcd.putstr("Counter:%d" %(count))
    time.sleep_ms(1000)
    count += 1

Moving back to the start of row 2 each loop and overwriting it lets the counter update in place rather than scrolling the screen.

Key Concepts

  • I2C bus scanning: i2c.scan() discovers devices and their addresses without hardcoding them
  • I2C-to-parallel backpacks: chips like the PCF8574 let an otherwise pin-hungry display (LCD1602 normally needs ~16 pins) run over just 2 wires
  • Cursor-addressed displays: move_to() + putstr() is the basic pattern for placing text anywhere on the screen

See Class I2cLcd for the full API reference.

Further Exploration

  • Display your own text on the screen. What happens if the text is too long to fit on the screen?
  • Make the text scroll

Back to Module

Adapted from Python_Tutorial.pdf Project 20.1