Das ist nicht sehr üblich.
Die hex Aderesen brauchst du zumeist nicht ändern.
Code:
#ifndef F_CPU
	#define F_CPU 16000000			/**< Change this to the clock-rate of your microcontroller */
#endif

#define wait1us	_delay_loop_1((F_CPU * 0.000001) / 3)	/**< 1 us delay */
#define wait1ms	_delay_loop_2((F_CPU * 0.001) / 4)	/**< 1 ms delay */
/*@}*/

//-------------------------------------------------------------------------------------------------------------------

#include <util/delay.h>
#include <stdbool.h>
#include <stdint.h> 
#include "i2cmaster.h"

//--Display-Configuration-Settings-----------------------------------------------------------------------------------

/** \defgroup DISPLAY_CONFIGURATION DISPLAY CONFIGURATION
 Change this settings to your configuration.
*/
/*@{*/
#define LCD_I2C_DEVICE		0x40	/**< Change this to the address of your expander */
#define LCD_LINES			4	    /**< Enter the number of lines of your display here */
#define LCD_ROWS			20	    /**< Enter the number of rows of your display here */

#define LCD_LINE1			0x00	/**< This should be 0x00 on all displays */
#define LCD_LINE2			0x20	/**< Change this to the address for line 2 on your display */
#define LCD_LINE3			0x40	/**< Change this to the address for line 3 on your display */
#define LCD_LINE4			0x60	/**< Change this to the address for line 4 on your display */
/*@}*/

//-------------------------------------------------------------------------------------------------------------------

//--The-following-definitions-are-corresponding-to-the-PIN-Assignment-(see-above)------------------------------------

/** \defgroup PIN_ASSIGNMENT PIN ASSIGNMENT
 This pin assignment shows how the display is connected to the PCF8574.
*/
/*@{*/
#define LCD_D4_PIN			3	/**< LCD-Pin DB4 is connected to P3 on the PCF8574 */
#define LCD_D5_PIN			2	/**< LCD-Pin DB5 is connected to P2 on the PCF8574 */
#define LCD_D6_PIN			1	/**< LCD-Pin DB6 is connected to P1 on the PCF8574 */
#define LCD_D7_PIN			0	/**< LCD-Pin DB7 is connected to P0 on the PCF8574 */
#define LCD_RS_PIN			7	/**< LCD-Pin  RS is connected to P7 on the PCF8574 */
#define LCD_RW_PIN			6	/**< LCD-Pin  RW is connected to P6 on the PCF8574 */
#define LCD_EMPTY_PIN		4	/**< this pin    is not connected */
#define LCD_E_PIN			5	/**< LCD-Pin   E is connected to P5 on the PCF8574 */
/*@}*/
Am Anfang die F_CPU einstellen
Unter Display-Configuration-Settings
Die I2C-Adresse des Port-Expander
Anzahl der Zeilen
Anzahl der Zeichen je Zeile

Unter Pin-Assignment
Hier musst du die Zuordnung der Expander-Pin zu den LCD-PIn machen

Sonst sollte für Standardfunktionen keine weitere Einstellung notwendig sein.
Bist du sicher das I2C überhaupt funktioniert