I picked up a couple of very low cost 16×2 LCD display modules for a project I am working on. They are based on the Texas Instruments PCF8574 Remote 8-Bit I/O Expander for I2C Bus. Since there are a myriad of different LCD libraries for Arduino, I thought I would document my experience and the working configuration I came upon.

The library we need is LiquidCrystal_PCF8574 by Matthias Hertel. It is available in the Arduino libraries manager.

The demo code from the library works well to demonstrate the capabilities of the display:
#include <LiquidCrystal_PCF8574.h>
#include <Wire.h>
LiquidCrystal_PCF8574 lcd(0x27); // set the LCD address to 0x27 for a 16 chars and 2 line display
int show = -1;
void setup()
{
int error;
Serial.begin(115200);
Serial.println("LCD...");
// wait on Serial to be available on Leonardo
while (!Serial)
;
Serial.println("Dose: check for LCD");
// See http://playground.arduino.cc/Main/I2cScanner how to test for a I2C device.
Wire.begin();
Wire.beginTransmission(0x27);
error = Wire.endTransmission();
Serial.print("Error: ");
Serial.print(error);
if (error == 0) {
Serial.println(": LCD found.");
show = 0;
lcd.begin(16, 2); // initialize the lcd
} else {
Serial.println(": LCD not found.");
} // if
} // setup()
void loop()
{
if (show == 0) {
lcd.setBacklight(255);
lcd.home();
lcd.clear();
lcd.print("Hello LCD");
delay(1000);
lcd.setBacklight(0);
delay(400);
lcd.setBacklight(255);
} else if (show == 1) {
lcd.clear();
lcd.print("Cursor On");
lcd.cursor();
} else if (show == 2) {
lcd.clear();
lcd.print("Cursor Blink");
lcd.blink();
} else if (show == 3) {
lcd.clear();
lcd.print("Cursor OFF");
lcd.noBlink();
lcd.noCursor();
} else if (show == 4) {
lcd.clear();
lcd.print("Display Off");
lcd.noDisplay();
} else if (show == 5) {
lcd.clear();
lcd.print("Display On");
lcd.display();
} else if (show == 7) {
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("*** first line.");
lcd.setCursor(0, 1);
lcd.print("*** second line.");
} else if (show == 8) {
lcd.scrollDisplayLeft();
} else if (show == 9) {
lcd.scrollDisplayLeft();
} else if (show == 10) {
lcd.scrollDisplayLeft();
} else if (show == 11) {
lcd.scrollDisplayRight();
} else if (show == 12) {
lcd.clear();
lcd.print("write-");
} else if (show > 12) {
lcd.print(show - 13);
} // if
delay(1400);
show = (show + 1) % 16;
} // loop()