Attempt on "Hello world!" with a 2004 LCD, I2C, PCF8574 and wiringPi

i2c LCD Hello world

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <time.h>

#include <wiringPi.h>
#include <pcf8574.h>
#include <lcd.h>

#define i2c_adress 0x27
#define af_base 100
#define af_rs (af_base + 0)
#define af_e (af_base + 2)
#define af_db4 (af_base + 4)
#define af_db5 (af_base + 5)
#define af_db6 (af_base + 6)
#define af_db7 (af_base + 7)

#define af_backlight (af_base + 3)

int main (int argc, char *argv[])
{
  int lcdHandle;

  wiringPiSetupSys () ;
  pcf8574Setup (af_base, i2c_adress) ;

  lcdHandle = lcdInit (2, 16, 4, af_rs, af_e, af_db4, af_db5, af_db6, af_db7, 0,0,0,0) ;

  pinMode(af_backlight, OUTPUT);
  digitalWrite(af_backlight, HIGH);

  lcdPosition (lcdHandle, 0, 0);
  lcdPuts (lcdHandle, "Hello World!");
}

If this code does not work for someone (the screen will blink, but there will be squares in the top line), then try setting the state of the pin rw

#define af_rw (af_base + 1)

pinMode(af_rw, OUTPUT);
digitalWrite(af_rw, LOW);