Hi, first post so please go easy on me 
I'm new to Arduino and I'm trying to drive a 20x4 LCD display with an I2C driver.
I've done quite a lot of reading and been through some excellent posts, but still have a problem and cannot determine whether something is wrong with my screen or if the screen is fine and I'm just driving it wrong.
I'll detail as much as I can hoping it will help find the cause and solution.
First step: identifying the I2C controller version. Following this topic: https://arduino-info.wikispaces.com/LCD-Blue-I2C I reckon it's a "version 3" albeit without the text.
Photo of my actual unit:
Close up of the I2C:
Now in trying to get it working, I ran the address identifier. Strangely enough, this appears to be 0x3f.
Setting 0x3f as the address in the v3 code seems to work: I do get the backlight turning on and off at the start. Any other address doesn't give any backlight control.
However, I don't get any text at all.
With the following code:
/* YourDuino.com Example Software Sketch
20 character 4 line I2C Display
Backpack Interface labelled "LCM1602 IIC A0 A1 A2"
terry@yourduino.com */
/*-----( Import needed libraries )-----*/
#include <Wire.h> // Comes with Arduino IDE
// Get the LCD I2C Library here:
// https://bitbucket.org/fmalpartida/new-liquidcrystal/downloads
// Move any other LCD libraries to another folder or delete them
// See Library "Docs" folder for possible commands etc.
#include <LiquidCrystal_I2C.h>
/*-----( Declare Constants )-----*/
//none
/*-----( Declare objects )-----*/
// set the LCD address to 0x20 for a 20 chars 4 line display
// Set the pins on the I2C chip used for LCD connections:
// addr, en,rw,rs,d4,d5,d6,d7,bl,blpol
LiquidCrystal_I2C lcd(0x3f, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); // Set the LCD I2C address
/*-----( Declare Variables )-----*/
//none
void setup() /*----( SETUP: RUNS ONCE )----*/
{
Serial.begin(9600); // Used to type in characters
lcd.begin(20,4); // initialize the lcd for 20 chars 4 lines and turn on backlight
// ------- Quick 3 blinks of backlight -------------
for(int i = 0; i< 3; i++)
{
lcd.backlight();
delay(250);
lcd.noBacklight();
delay(250);
}
lcd.backlight(); // finish with backlight on
//-------- Write characters on the display ----------------
// NOTE: Cursor Position: CHAR, LINE) start at 0
lcd.setCursor(3,0); //Start at character 4 on line 0
lcd.print("Hello, world!");
delay(1000);
lcd.setCursor(2,1);
lcd.print("From YourDuino");
delay(1000);
lcd.setCursor(0,2);
lcd.print("20 by 4 Line Display");
lcd.setCursor(0,3);
delay(2000);
lcd.print("http://YourDuino.com");
delay(8000);
// Wait and then tell user they can start the Serial Monitor and type in characters to
// Display. (Set Serial Monitor option to "No Line Ending")
lcd.setCursor(0,0); //Start at character 0 on line 0
lcd.print("Start Serial Monitor");
lcd.setCursor(0,1);
lcd.print("Type chars 2 display");
}/*--(end setup )---*/
void loop() /*----( LOOP: RUNS CONSTANTLY )----*/
{
{
// when characters arrive over the serial port...
if (Serial.available()) {
// wait a bit for the entire message to arrive
delay(100);
// clear the screen
lcd.clear();
// read all the available characters
while (Serial.available() > 0) {
// display each character to the LCD
lcd.write(Serial.read());
}
}
}
}/* --(end main loop )-- */
/* ( THE END ) */
I end up with this:
I did try some other code I found and that produced simlilar results, although the second and fourth lines were left completely blank:
I'll carry on researching this, but thought I'd ask here as it seems several people have similar issues with backlight blanking OK but not much more.
