GSM shield + Adruino2009 e PCF8574

Hi all,

I just finished preparing my circuit using two PCF8574 to manage a 16x2 LCD and a keypad 4x4 course in I2C … connecting to my Arduino 2009 ,plug Power 5v SDA and SCL to pin A4 and A5 but i can not read the display pressed keys on the keypad.

Without the Seeedstudio GSM Sim900 everything work, i have try to change every possible address about PCF8574 but nothing.

[code]#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Keypad_I2C.h>
#include <Keypad.h>
#include <Wire.h>

LiquidCrystal_I2C lcd(0x20,16,2); // set the LCD address to 0x20 for a 16 chars and 2 line display

#define I2CADDR 0x24

const byte ROWS = 4;
const byte COLS = 4;

char hexaKeys[ROWS][COLS] = {
byte rowPins[ROWS] = {7, 6, 5, 4};
byte colPins[COLS] = {3, 2, 1, 0};

Keypad_I2C customKeypad( makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS, I2CADDR);

void setup()
lcd.init(); // initialize the lcd
customKeypad.begin( );

void loop()
char customKey = customKeypad.getKey();

if (customKey != NO_KEY){


Any ideas