user14770: I've been playing with an Arduino Uno, trying to get a 16x2 LCD screen to work with an I2C controller. I've got this LCD screen and this controller. And I've been trying to get the sketch below to work.
#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,2,1,0,4,5,6,7,3,POSITIVE);//, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);
void setup()
{
    lcd.begin(16,2);
    lcd.backlight();
    lcd.setCursor(0, 0);
    lcd.print("Hello world!");
    lcd.setCursor(0, 1);
    lcd.print("Row number: ");
    lcd.setCursor(12, 1);
    lcd.print("2");
}
void loop()
{

}

I've used an address scanner to verify that the address is correct (39 [0x27]), but it still won't display anything. It lights up, and I've tried adjusting the contrast, but it just won't display any characters.
I'm wondering if the definition of which pins are which is correct, but I can't seem to find anything detailing how the numbers used in the sketch correlate to the pins on the controller, which then correlate to the pins on the LCD screen. If any body can give me some insight I'd appreciate it.

user11174: Yes, the pins can be different depending on the LCD and the controller. My favorite solution to this is to run a simple "i2c guesser" sketch that can be downloaded from the following forum thread (download link is at the bottom of the first post):
http://forum.arduino.cc/index.php?topic=260510.0
With that sketch it usually only takes me a couple minutes to find the correct pin numbers. 

14770: <p>I've been playing with an Arduino Uno, trying to get a 16x2 LCD screen to work with an I2C controller. I've got <a href="http://rads.stackoverflow.com/amzn/click/B00HICXURS" rel="nofollow">this</a> LCD screen and <a href="http://rads.stackoverflow.com/amzn/click/B00FIVUVBY" rel="nofollow">this</a> controller. And I've been trying to get the sketch below to work.</p>

<pre><code>#include &lt;Wire.h&gt;
#include &lt;LCD.h&gt;
#include &lt;LiquidCrystal_I2C.h&gt;
LiquidCrystal_I2C lcd(0x27,2,1,0,4,5,6,7,3,POSITIVE);//, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);
void setup()
{
    lcd.begin(16,2);
    lcd.backlight();
    lcd.setCursor(0, 0);
    lcd.print("Hello world!");
    lcd.setCursor(0, 1);
    lcd.print("Row number: ");
    lcd.setCursor(12, 1);
    lcd.print("2");
}
void loop()
{

}
</code></pre>

<p>I've used an address scanner to verify that the address is correct (39 [0x27]), but it still won't display anything. It lights up, and I've tried adjusting the contrast, but it just won't display any characters.</p>

<p>I'm wondering if the definition of which pins are which is correct, but I can't seem to find anything detailing how the numbers used in the sketch correlate to the pins on the controller, which then correlate to the pins on the LCD screen. If any body can give me some insight I'd appreciate it.</p>
 11174: <p>Yes, the pins can be different depending on the LCD and the controller. My favorite solution to this is to run a simple "i2c guesser" sketch that can be downloaded from the following forum thread (download link is at the bottom of the first post):
<a href="http://forum.arduino.cc/index.php?topic=260510.0" rel="nofollow">http://forum.arduino.cc/index.php?topic=260510.0</a></p>

<p>With that sketch it usually only takes me a couple minutes to find the correct pin numbers. </p>
