Hi.
I'm a beginner with Arduino programming and need some advice.
First of all I want to give my apologies because of my english and my programming capabilities.
I'm using Fingerprint sensor that works with AT Commands. one of the AT Commands is "AT+ADD=xxxx"; which xxxx is a 4 digit number.
this command adds a new finger template to the memory of FP sensor. (ex:AT+ADD=0012, this command stores a finger template to 0012!! )
What I need is to read 4 digit numbers via ttp229 touch keypad and then add "AT+ADD=" to it
and just send it via serial to FP sensor.
the code I use is:
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x3f,16 ,2); // set the LCD address to 0x3f for a 16 chars and 2 line display
#include <SoftwareSerial.h>
SoftwareSerial FP(2, 3);
#define SCL_PIN 9
#define SDO_PIN 10
/* Used to store the key state */
byte Key;
void setup() {
/* Configure the clock and data pins */
pinMode(SCL_PIN, OUTPUT);
pinMode(SDO_PIN, INPUT);
pinMode(12,OUTPUT); // just a LED to let u know a key is touched.
Serial.begin(19200);
FP.begin(9600);
lcd.init();
lcd.backlight();
delay(100);
}
void loop() {
Key = Read_Keypad(); //read from keypad
if (Serial.available()) {
delay(100);
FP.write(Serial.read());
}
while (FP.available()>0) {
char i = FP.read();
Serial.write(i);
lcd.print(i);
}
if (Key == 11){
digitalWrite(12,1);
lcd.clear();
FP.println("AT+CHECK"); // cheking finger template, works fine.
} else {
digitalWrite(12,0);
}
if (Key == 12){
digitalWrite(12,1);
lcd.clear();
FP.println("AT"); // gives version of FP sensor, works fine.
} else {
digitalWrite(12,0);
}
if (Key == 13){
digitalWrite(12,1);
lcd.clear();
FP.println("AT+EMPTYMEM?"); // gives empty memories, works fine.
} else {
digitalWrite(12,0);
}
if (Key == 14){
digitalWrite(12,1);
lcd.clear();
GenerateCommand(); // HERE IS THE PROBLEM :(
} else {
digitalWrite(12,0);
}
}
byte Read_Keypad(void)
{
byte Count;
byte Key_State = 0;
/* Pulse the clock pin 16 times (one for each key of the keypad)
and read the state of the data pin on each pulse */
for(Count = 1; Count <= 16; Count++)
{
digitalWrite(SCL_PIN, LOW);
/* If the data pin is low (active low mode) then store the
current key number */
if (!digitalRead(SDO_PIN))
Key_State = Count;
digitalWrite(SCL_PIN, HIGH);
}
return Key_State;
}
// generating ("AT+ADD=xxxx") & send it to Fingerprint
String GenerateCommand() {
String command;
String temp;
int num=Get4digit();
if (num < 1000) {
temp=String(num, DEC);
temp=String("0"+temp);
} else {
temp=String(num, DEC);
}
command=String("AT+ADD="+temp);
}
int Get4digit(){
int num = 0;
Key = Read_Keypad();
int counter = 0;
while (counter < 4){
switch (Key){
case 1: case 2: case 3: case 4: case 5:
case 6: case 7: case 8: case 9:
num = num * 10 + (int)Key;
break;
case 10:
num = num * 10;
break;
}
delay(150);
Key = Read_Keypad();
counter++;
}
return num;
}
I use number 10 of keypad as zero, since it doesn't have zero number.
when I touch key num 14 it just gives "AT+ADD=00"
I don't know how to solve it 
please help me thank you in advance..... 