Boa tarde galera, sou novato com arduino , e estou com dificuldade de trabalhar com o lcd 20 x 4 , ele nao escreve oq eu mando , ja descobri o id dele e configurei e msm assim ele nao funciona , esta embaixo o codiogo , se alguem puder me ajudar ficarei muito grato . 

[code]
/*
#####################################################################################
# File: Arduino_Watering_sustem.ino
# Processor: Arduino UNO, MEGA ou Teensy++ 2.0
# Language: Wiring / C /Processing /Fritzing / Arduino IDE
#
# Objectives: Watering System - Irrigation
#
# Behavior: When the soil is dry,
#
#
#
# Author: Marcelo Moraes
# Date: 12/10/12
# place: Brazil, Sorocaba City
#
#####################################################################################

This project contains public domain code.
The modification is allowed without notice.

*/

// libraries definition
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include "RTClib.h"

// frequency musical notes
#define NOTE_C6 1047
#define NOTE_C3 131
#define NOTE_G3 196

// pins definition
int levelSensorPin = 0;
int moistureSensorPin = 1;
int audioPin = 2;
int soggyLEDPin = 3;
int moistsoilLEDPin = 4;
int drysoilLEDPin = 5;
int pumpLEDPin = 6;
int pumpPin = 7;

// variables
int levelSensorValue; // stores the level sensor values
int moistureSensorValue; // stores the moisture sensor values
int j = 0;

// system messages
const char *string_table[] =
{
" Welcome! =)",
" Tank LOW level",
" Dry soil",
" Moist soil",
" Soggy soil",
"The water pump is on",
" ArduinoByMyself",
" Watering System",
" Please wait!"
};

// objects definition
RTC_DS1307 RTC;
LiquidCrystal_I2C lcd(0x3F, 20, 4);

void setup() {
// serial initialization
Serial.begin(9600);

// LCD initialization
lcd.init();
lcd.backlight(); // with Backlight
lcd.clear(); // clearscreen

// Wire initialization
Wire.begin();

// RTC initialization
RTC.begin();
if (!RTC.isrunning()) {
// date and time adjust as the PC computer date and time
RTC.adjust(DateTime(__DATE__, __TIME__));
}

// Arduino pins initalization
pinMode(audioPin, OUTPUT);
pinMode(soggyLEDPin, OUTPUT);
pinMode(moistsoilLEDPin, OUTPUT);
pinMode(drysoilLEDPin, OUTPUT);
pinMode(pumpLEDPin, OUTPUT);
pinMode(pumpPin, OUTPUT);

// LCD initial messages
lcd.clear();
lcd.setCursor(0, 0);
lcd.print(string_table[6]);
lcd.setCursor(0, 1);
lcd.print(string_table[7]);
lcd.setCursor(0, 3);
lcd.print(string_table[0]);
// initialization delay
delay(5000);
}

void loop() {

// RTC parameters definition
DateTime myRTC = RTC.now();
int H = myRTC.hour();
int M = myRTC.minute();
int S = myRTC.second();

// call Clock Function
//RightHour();

// reads the sensors
levelSensorValue = analogRead(levelSensorPin);
moistureSensorValue = analogRead(moistureSensorPin);

// if low water level: plays the low level alarm
if (levelSensorValue > 600) {
// system messages
lcd.clear();
RightHour();
lcd.setCursor(0, 3);
lcd.print(string_table[1]);
// plays the alarm sound
for (int i = 0; i < 2; i++) {
tone(audioPin, NOTE_G3, 200);
delay(200);
tone(audioPin, NOTE_C3, 200);
delay(200);
noTone(audioPin);
}
}

// check the moisture range
if (moistureSensorValue >= 700) {
// in case of dry soil:
// system messages
lcd.clear();
RightHour();
lcd.setCursor(0, 3);
lcd.print(string_table[2]);
// lights up the correct LED
digitalWrite(drysoilLEDPin, HIGH);
digitalWrite(moistsoilLEDPin, LOW);
digitalWrite(soggyLEDPin, LOW);
// plays the alarm sound
tone(audioPin, NOTE_C6, 100);
delay(250);
noTone(audioPin);
}
if ((moistureSensorValue < 700) && (moistureSensorValue >= 300)) {
// in case of moist soil:
// system messages
lcd.clear();
RightHour();
lcd.setCursor(0, 3);
lcd.print(string_table[3]);
// lights up the correct LED
digitalWrite(drysoilLEDPin, LOW);
digitalWrite(moistsoilLEDPin, HIGH);
digitalWrite(soggyLEDPin, LOW);
delay(250);
}
if (moistureSensorValue < 300) {
// in case of soggy soil:
// system messages
lcd.clear();
RightHour();
lcd.setCursor(0, 3);
lcd.print(string_table[4]);
// lights up the correct LED
digitalWrite(drysoilLEDPin, LOW);
digitalWrite(moistsoilLEDPin, LOW);
digitalWrite(soggyLEDPin, HIGH);
delay(100);
}

// if the soil is dry and if it is the right time: turn on the pump for 1 minute
if ((H == 16) && (M == 50) && (S == 00)) {
while (moistureSensorValue >= 700) {
// system messages
lcd.clear();
RightHour();
lcd.setCursor(0, 1);
lcd.print(string_table[8]);
lcd.setCursor(0, 3);
lcd.print(string_table[5]);
// turn the pump on
digitalWrite(pumpPin, HIGH);
digitalWrite(pumpLEDPin, HIGH);
delay(10000);
// if the soil is not moist so far
// reads the moisture sensor once more
moistureSensorValue = analogRead(moistureSensorPin);
}
// turn the pump off
digitalWrite(pumpPin, LOW);
digitalWrite(pumpLEDPin, LOW);
}

}

// Real Time Clock Function
void RightHour()
{
DateTime Now = RTC.now();
String clock_date = " Date: ";
String clock_hour = " Time: ";

int _day = Now.day();
int _month = Now.month();
int _year = Now.year();

clock_date += fixZero(_day);
clock_date += "/";
clock_date += fixZero(_month);
clock_date += "/";
clock_date += _year;

int _hour = Now.hour();
int _minute = Now.minute();
int _second = Now.second();

clock_hour += fixZero(_hour);
clock_hour += ":";
clock_hour += fixZero(_minute);
clock_hour += ":";
clock_hour += fixZero(_second);

lcd.clear();
lcd.setCursor(0, 0);
lcd.print(clock_date);
lcd.setCursor(0, 1);
lcd.print(clock_hour);

delay(500);
}

String fixZero(int i)
{
String ret;
if (i < 10) ret += "0";
ret += i;
return ret;
}

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