Read analoge sensor - display on LCD

// A very primitive example of how to read from analogue ports and display values on a LCD display
//
// Note: There are known errors of not cleaning old numbers before writing new numbers

// /*****\  Libraries (and/or files) to be included: /*****\

// needed for the I2C_LCD to work
#include <Wire.h>               // Comes with Arduino IDE (provides the basic I2C communications)
#include <LiquidCrystal_I2C.h>  // MUST be the latest library from: https://bitbucket.org/fmalpartida/new-liquidcrystal/wiki/Home

// /*****\ Variables to be used in this sketch (program)  /*****\

//***** I2C_LCD details *****

// Set the pins on the I2C chip used for LCD connections:
// LiquidCrystal_I2C lcd(addr, en, rw, rs, d4, d5, d6, d7, bl, blpol)
// I2C board marked: "YwRobot Arduino LCM1602 IIC V1" and
// I2C board marked: no markings, but a0, a1 & A2 are dual sodlerpads under the blue potentiometer,
//                   and a jumper is marked LED. Bought on ebay from seller: mxqtech
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);  // Set the LCD I2C address


//***** Analog variables *****
const int analogInPin1 = A1;  // Analog input pin
const int analogInPin2 = A2;  // Analog input pin
const int analogInPin3 = A3;  // Analog input pin
int sensorValue1_raw = 0;
int sensorValue2_raw = 0;
int sensorValue3_raw = 0;
float sensorValue1 = 0;
float sensorValue2 = 0;
float sensorValue3 = 0;


/**************************************************************************/
// Arduino SETUP - is run Once, after the Arduino has been reset.
/**************************************************************************/
void setup() {
  // set up the LCD's number of columns and rows:
  lcd.begin(20,4);   // initialize the lcd for 20 chars 4 lines,
  lcd.backlight();   // turn on backlight
  // Print a message to the LCD.
  // lcd.print("hello, world!");

}


/**************************************************************************/
// Arduino LOOP procedure - continues to be repeated, until power off or
/**************************************************************************/
void loop() {
  read_sensors();
  convert_readings();
  display_readings();
}


/**************************************************************************/
// Functions that does all the work
/**************************************************************************/
void read_sensors(){
  sensorValue1_raw = analogRead(analogInPin1);
  sensorValue2_raw = analogRead(analogInPin2);
  sensorValue3_raw = analogRead(analogInPin3);
}

void convert_readings(){
  // Here we need to make a conversion of the raw value (0-1023) to a decimal value
  // that relates the raw sensor value to whatever measurement is used in the tube being sensed/measured.
  // Here it is also possible to trimm with calibration values
  sensorValue1 = (sensorValue1_raw - 205) * 2.69;  // 205 and 2.69 are here random numbers, but in real life will be usefull values
  sensorValue2 = (sensorValue2_raw - 205) * 2.69;
  sensorValue3 = (sensorValue3_raw - 205) * 2.69;
}

void display_readings(){
  int a = 0;
  // NOTE: Cursor Position: (CHAR, LINE) start at 0
  lcd.setCursor(0,1); //Start at character 0 on line 1
  lcd.print( sensorValue1_raw );
  //discovering number of digits before the decimal point
  if (sensorValue1 > 999) a = 0;
  else if (sensorValue1 > 99) a = 1;
  else if(sensorValue1 > 9) a = 2;
  lcd.setCursor(0, 7 + a);
  lcd.print( sensorValue1 );

  lcd.setCursor(0,2); //Start at character 0 on line 2
  lcd.print( sensorValue2_raw );
  //discovering number of digits before the decimal point
  if (sensorValue2 > 999) a = 0;
  else if (sensorValue2 > 99) a = 1;
  else if(sensorValue2 > 9) a = 2;
  lcd.setCursor(0, 7 + a);
  lcd.print( sensorValue2 );

  lcd.setCursor(0,3); //Start at character 0 on line 3
  lcd.print( sensorValue3_raw );
  //discovering number of digits before the decimal point
  if (sensorValue3 > 999) a = 0;
  else if (sensorValue3 > 99) a = 1;
  else if(sensorValue3 > 9) a = 2;
  lcd.setCursor(0, 7 + a);
  lcd.print( sensorValue3 );
}