Hi!
I’m beginner at programming and I don’t know why not works my code… Arduino Uno+fingerprint sensor+I2C LCD… 
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);
#include <Adafruit_Fingerprint.h>
#if ARDUINO >= 100
#include <SoftwareSerial.h>
#else
#include <NewSoftSerial.h>
#endif
uint8_t getFingerprintEnroll(uint8_t id);
int k;
// pin #2 is IN from sensor (GREEN wire)
// pin #3 is OUT from arduino (WHITE wire)
#if ARDUINO >= 100
SoftwareSerial mySerial(2, 3);
#else
NewSoftSerial mySerial(2`, 3);
#endif
Adafruit_Fingerprint finger = Adafruit_Fingerprint(&mySerial);
uint8_t id = 0;
void setup()
{
while (!Serial); // For Yun/Leo/Micro/Zero/...
lcd.begin(16, 2);
lcd.print("Hello, World");
delay(1000);
lcd.clear();
Serial.begin(9600);
lcd.println("Finger test");
delay(1000);
//mySerial.print("Detect");
// set the data rate for the sensor serial port
finger.begin(57600);
//mySerial.print("Detect");
if (finger.verifyPassword()) {
Serial.println("Found fingerprint sensor!");
} else {
Serial.println("Did not find fingerprint sensor :(");
while (1);
}lcd.clear();
}
void loop()
// run over and over again
{
lcd.clear();
lcd.println("Take your finger!");
Serial.print(" ID=0" );
//lcd.print(k);
// while (true) {
// while (! Serial.available());
// char c = Serial.read();
// if (! isdigit(c)) break;
// id *= 10;
// id += c - '0';
// }
id++;
lcd.print("Enrolling ID #");
lcd.println(id); // serial volt
lcd.print(id); // serial volt
while (! getFingerprintEnroll(id) );
}
uint8_t getFingerprintEnroll(uint8_t id) {
uint8_t p = -1;
Serial.println("Waiting for valid finger to enroll");
Serial.print("Put the Finger");
while (p != FINGERPRINT_OK) {
p = finger.getImage();
switch (p) {
case FINGERPRINT_OK:
Serial.println("Image taken");
break;
case FINGERPRINT_NOFINGER:
Serial.println(".");
break;
case FINGERPRINT_PACKETRECIEVEERR:
Serial.println("Communication error");
break;
case FINGERPRINT_IMAGEFAIL:
Serial.println("Imaging error");
break;
default:
Serial.println("Unknown error");
break;
}
}
// OK success!
p = finger.image2Tz(1);
switch (p) {
case FINGERPRINT_OK:
Serial.println("Image converted");
break;
case FINGERPRINT_IMAGEMESS:
Serial.println("Image too messy");
return p;
case FINGERPRINT_PACKETRECIEVEERR:
Serial.println("Communication error");
return p;
case FINGERPRINT_FEATUREFAIL:
Serial.println("Could not find fingerprint features");
return p;
case FINGERPRINT_INVALIDIMAGE:
Serial.println("Could not find fingerprint features");
return p;
default:
Serial.println("Unknown error");
return p;
}
Serial.println("Remove finger");
delay(2000);
p = 0;
while (p != FINGERPRINT_NOFINGER) {
p = finger.getImage();
}
p = -1;
Serial.println("Place same finger again");
while (p != FINGERPRINT_OK) {
p = finger.getImage();
switch (p) {
case FINGERPRINT_OK:
{
Serial.println("Image taken");
break;
}
case FINGERPRINT_NOFINGER:
Serial.print(".");
break;
case FINGERPRINT_PACKETRECIEVEERR:
Serial.println("Communication error");
break;
case FINGERPRINT_IMAGEFAIL:
Serial.println("Imaging error");
break;
default:
Serial.println("Unknown error");
break;
}
}
// OK success!
p = finger.image2Tz(2);
switch (p) {
case FINGERPRINT_OK:
Serial.println("Image converted");
break;
case FINGERPRINT_IMAGEMESS:
Serial.println("Image too messy");
return p;
case FINGERPRINT_PACKETRECIEVEERR:
Serial.println("Communication error");
return p;
case FINGERPRINT_FEATUREFAIL:
Serial.println("Could not find fingerprint features");
return p;
case FINGERPRINT_INVALIDIMAGE:
Serial.println("Could not find fingerprint features");
return p;
default:
Serial.println("Unknown error");
return p;
}
// OK converted!
p = finger.createModel();
if (p == FINGERPRINT_OK) {
Serial.println("Prints matched!");
} else if (p == FINGERPRINT_PACKETRECIEVEERR) {
Serial.println("Communication error");
return p;
} else if (p == FINGERPRINT_ENROLLMISMATCH) {
Serial.println("Fingerprints did not match");
return p;
} else {
Serial.println("Unknown error");
return p;
}
p = finger.storeModel(id);
if (p == FINGERPRINT_OK) {
Serial.println("Stored!");
} else if (p == FINGERPRINT_PACKETRECIEVEERR) {
Serial.println("Communication error");
return p;
} else if (p == FINGERPRINT_BADLOCATION) {
Serial.println("Could not store in that location");
return p;
} else if (p == FINGERPRINT_FLASHERR) {
Serial.println("Error writing to flash");
return p;
} else {
Serial.println("Unknown error");
return p;
}
}