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4.1. LCD Message Display

Under construction
Short example demonstration video

This example shows how to connect and use the I2C 16x2 LCD Display with the NULA Mini board. We will be using a simple pushbutton to measure the time difference between two presses and update the display accordingly.

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At the end of this example you will learn:

  • How to connect 16x2 LCD display
  • How to display data and update it
  • How to measure time difference
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Parts required:

  • Soldered NULA Mini Board
  • Breadboard
  • 16x2 LCD Display
  • 1 x Pushbutton
  • 1 x Qwiic cable
  • Some jumper wires
Under construction
Required components

Putting the components together​

  • Place the pushbutton on the breadboard, connect one side of the terminal to pin 5, and the other opposite side to GND.
  • Connect the LCD via Qwiic cable to the NULA Mini board
Under construction
Components connected together

Code Example​

Import LCD driver with other necessary modules.

from LCD import LCD_I2C
from machine import I2C, Pin
import time

Create a LCD_I2C object and initialize it over I2C using Qwiic cable.

i2c = I2C(0, scl=Pin(7), sda=Pin(6))
lcd = LCD_I2C(i2c)

# Initialize sensor over Qwiic
# lcd = LCD_I2C()

Turn on the backlight of the LCD and start communication over I2C.

lcd.backlight()
lcd.begin()

Initialize the button on pin 5 and use internal PULL-UP to set the pin HIGH (1) while not pressed.

BUTTON_PIN = 5
btn = Pin(BUTTON_PIN, Pin.IN, Pin.PULL_UP)

Here we print initial text on the display. Indexing on both row and column start at 0, to print a character or message in the third column and first row we set the cursor to (2, 0). For first column in second row set the cursor to (0, 1).

# Sets the cursor to the third character place in the first row
lcd.setCursor(2, 0)
lcd.print("Hello, World!")

# Sets the cursor to the first character place in the second row
lcd.setCursor(0, 1)
lcd.print("Press the button")

Define variables last_press_MS to hold the last time button was pressed (in milliseconds) and DEBOUNCE_MS for button debounce time. We also set the first print flag to True to see if button was pressed for the first time or was already pressed.

last_press_MS = time.ticks_ms()
DEBOUNCE_MS = 30

isFirstPrint = True

Now we define the function that will be used for printing the elapsed time from button presses. If a button was pressed, function is called which formats the elapsed time in mm:ss format and overwrites the previous info on the display, this way we don't have to use lcd.clear() every single time ensuring smooth display update.

def print_time_lcd(elapsed_time_s, isFirstPrint):
    # Check if button is pressed for first time, print accordingly
    if isFirstPrint:
        lcd.clear()
        lcd.setCursor(0, 0)
        lcd.print("Elapsed time: ")
    # Set cursor to point to first character in second row
    lcd.setCursor(0, 1)
    # Check if more than a minute has passed
    if elapsed_time_s < 60:
        # Print time in seconds format
        msg = "{:6.2f} s".format(elapsed_time_s)
    else:
        # Print time in MM:SS format
        minutes = int(elapsed_time_s / 60)
        seconds = int(elapsed_s % 60)
        msg = "{:02d}:{:02d} min".format(minutes, seconds)
    # Overwrite old text
    msg = (msg + " " * 16)[:16]
    # Print new text
    lcd.print(msg)

Main loop of the program where button state is constantly checked, when a button is pressed time.ticks_diff() is called to return difference between current time and last button press time and converts it to seconds. That value is then passed to print_time_lcd function. Additional debounce is added to count only one press.

while True:
    # Get current button state
    current_state = btn.value()
    # Check if button was pressed
    if current_state == 1:
        time.sleep_ms(DEBOUNCE_MS) # Debounce
        if btn.value() == 0: # Additional debounce check to count only one press
            # Get elapsed time from last press in seconds
            elapsed_s = time.ticks_diff(time.ticks_ms(), last_press_MS) / 1000.0
            # Print elapsed time on LCD
            print_time_lcd(elapsed_s, isFirstPrint)
            isFirstPrint = False
        
            # Reset timer
            last_press_MS = time.ticks_ms()
            
            # Wait until button is released to avoid repeated triggers
            while btn.value() == 0:
                time.sleep_ms(10)

Full Example​

4.1_LCD_Message_Display.py