Documentation

// LCD2004 20x4 Character LCD - Arduino Example (4-bit mode)
// RS->12, E->11, D4->5, D5->4, D6->3, D7->2, RW->GND

#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);   // RS, E, D4, D5, D6, D7
unsigned long count = 0;

void setup() {
  lcd.begin(20, 4);                      // 20 columns, 4 rows
  lcd.setCursor(0, 0);
  lcd.print("ShillehTek LCD2004");
  lcd.setCursor(0, 1);
  lcd.print("20 x 4 characters");
  lcd.setCursor(0, 2);
  lcd.print("HD44780 4-bit mode");
}

void loop() {
  lcd.setCursor(0, 3);
  lcd.print("Uptime: ");
  lcd.print(count++);
  lcd.print(" s   ");
  delay(1000);
}

// LCD2004 20x4 Character LCD - ESP32 Example (4-bit mode)
// RS->13, E->12, D4->14, D5->27, D6->26, D7->25, RW->GND, VDD->5V

#include <LiquidCrystal.h>

LiquidCrystal lcd(13, 12, 14, 27, 26, 25);
unsigned long count = 0;

void setup() {
  lcd.begin(20, 4);
  lcd.setCursor(0, 0);
  lcd.print("ESP32 + LCD2004");
  lcd.setCursor(0, 1);
  lcd.print("Write-only is safe:");
  lcd.setCursor(0, 2);
  lcd.print("RW tied to GND");
}

void loop() {
  lcd.setCursor(0, 3);
  lcd.print("Count: ");
  lcd.print(count++);
  lcd.print("   ");
  delay(1000);
}

#!/usr/bin/env python3
# LCD2004 20x4 Character LCD - Raspberry Pi Example (RPLCD, 4-bit GPIO)
# RS->GPIO26, E->GPIO19, D4-D7->GPIO13/6/5/11, RW->GND, VDD->5V
# Install: pip3 install RPLCD RPi.GPIO

import time
from RPLCD.gpio import CharLCD
import RPi.GPIO as GPIO

lcd = CharLCD(numbering_mode=GPIO.BCM,
              cols=20, rows=4,
              pin_rs=26, pin_e=19,
              pins_data=[13, 6, 5, 11],
              auto_linebreaks=True)

lcd.clear()
lcd.write_string("ShillehTek LCD2004")
lcd.cursor_pos = (1, 0)
lcd.write_string("Raspberry Pi + RPLCD")
lcd.cursor_pos = (2, 0)
lcd.write_string("20 columns x 4 rows")

count = 0
try:
    while True:
        lcd.cursor_pos = (3, 0)
        lcd.write_string("Uptime: {} s   ".format(count))
        count += 1
        time.sleep(1)
except KeyboardInterrupt:
    lcd.clear()
    GPIO.cleanup()
    print("Stopped by user")

# LCD2004 20x4 Character LCD - Pico MicroPython Example (4-bit mode)
# RS->GP16, E->GP17, D4-D7->GP18/19/20/21, RW->GND, VDD->VBUS(5V)

from machine import Pin
import time

RS = Pin(16, Pin.OUT)
E  = Pin(17, Pin.OUT)
DATA = [Pin(p, Pin.OUT) for p in (18, 19, 20, 21)]   # D4..D7
ROW_ADDR = (0x00, 0x40, 0x14, 0x54)                  # 20x4 row offsets

def pulse():
    E.value(1); time.sleep_us(2)
    E.value(0); time.sleep_us(50)

def write4(nib):
    for i in range(4):
        DATA[i].value((nib >> i) & 1)
    pulse()

def write_byte(b, rs):
    RS.value(rs)
    write4(b >> 4)
    write4(b & 0x0F)

def cmd(b):  write_byte(b, 0); time.sleep_ms(2)
def char(c): write_byte(ord(c), 1)

def lcd_init():
    time.sleep_ms(40)
    RS.value(0)
    for _ in range(3):
        write4(0x03); time.sleep_ms(5)
    write4(0x02)              # 4-bit mode
    cmd(0x28)                 # 2-line logical, 5x8 font
    cmd(0x0C)                 # display on, cursor off
    cmd(0x06)                 # entry mode: increment
    cmd(0x01)                 # clear
    time.sleep_ms(2)

def goto(row, col):
    cmd(0x80 | (ROW_ADDR[row] + col))

def text(row, s):
    goto(row, 0)
    for c in s[:20]:
        char(c)

lcd_init()
text(0, "ShillehTek LCD2004")
text(1, "Pico MicroPython")
text(2, "4-bit, RW to GND")

count = 0
while True:
    text(3, "Uptime: {} s".format(count))
    count += 1
    time.sleep(1)