/*
  Project: Gas detection with output on LCD with I2C Backpack
  Project Description:
  This sketch writes readings read from the Gas sensor to an LCD display module.
  This sketch is for a 16x4 screen.

  Author: STEMVentor Educonsulting
  
  This code is copyrighted. Please do not reuse or share for any purpose other than for learning with subscribed STEMVentor programs.
  This code is for educational purposes only and is not for production use.
*/

// LIBRARIES

//used for communicating with I2C devices
#include <Wire.h> 

//https://www.arduino.cc/reference/en/libraries/liquidcrystal-i2c/
// Install the LiquidCrystal I2C by Frank de Brabander from the IDE library manager. 
#include <LiquidCrystal_I2C.h>
 

// PIN DEFINITIONS

// GLOBAL VARIABLES
// Define the display size
const byte rows = 4;
const byte cols = 20;

// Used for reading a string.
String sensor_value;

// define the pin to which the gas sensor is connected
#define GAS_SENSOR_PIN 2


/* INITIALIZE OBJECTS
 * Libraries usually follow an object-oriented approach that requires
 * an instance of the class to call its methods.
 */
/* 
 * All I2C components have an address, the default is usually 0x27
 * If that doesn't work, see this:https://playground.arduino.cc/Main/I2cScanner/
 * The init statement accepts the address and the number of columns and rows.
 */
LiquidCrystal_I2C lcd(0x27, cols, rows);

/* LOCAL FUNCTIONS */

// Read Sensor value
void readSensorValue(){
  delay(1000);
  float gas_value = analogRead(GAS_SENSOR_PIN);
  sensor_value = "measured gas  = "  + String(map(gas_value, 4048, 0, 100, 0)) + "%";
}

/*
  Function to print to LCD on a single row.
  Takes the row number and the text to display on that row (max 20 chars, rest will be truncated).
  The entire display is cleared if the clear_all flag is true, else only the row is cleared (the default).
 */
void printToLCDByRow(int row, String text, bool clear_all = false){
  const char* twenty_spaces = "                    ";

  if(clear_all){ 
    lcd.clear(); //clears the entire display
  } 

  lcd.setCursor(0, row-1);
  lcd.print(twenty_spaces); //clears the row
  lcd.setCursor(0, row-1); //cursor has to be set again after printing spaces
  lcd.print(text);
}

/*
 Function to print to LCD across rows with each row having 20 chars.
 Messages can be a maximum of 20x4 chars, rest will betruncated.
 The entire display is cleared before printing the text.
 Test string of 20 char:
 12345678901234567890
 Test strings of 80 chars: 
 12345678901234567890123456789012345678901234567890123456789012345678901234567890
 Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec varius est donec.

 */
void printToLCD(String text){
  lcd.clear(); //clears the entire display

  byte chars_remaining = text.length();
  byte char_from = 0;
  byte char_to = chars_remaining < cols ? text.length() : char_from + cols;
  byte row = 1;

  while(chars_remaining > 0){
    String line = text.substring(char_from, char_to);
    printToLCDByRow(row, line);

    chars_remaining = text.length() - char_to;
    char_from = char_to;
    char_to = chars_remaining < cols ? text.length() : char_from + cols;
    row++;
  }

  Serial.println("Data string has been displayed on LCD");
}

/* SETUP CODE: runs once when the board starts up or resets */ 
void setup() {
  // Initializing wire
  Wire.begin();
  // Start the serial communication with baud rate suitable for your components.
  Serial.begin(9600);
  //Define the pinmode
  pinMode(GAS_SENSOR_PIN , INPUT);
  // Initialize the LCD.
  lcd.init();
  // Turn on the blacklight and print a message.
  lcd.backlight();
  // Use the function to display text on each line indiviudally.
  printToLCDByRow(1, "I2C LCD Ready!", true);
  printToLCDByRow(2, "Enter some text.", false);
  printToLCDByRow(3, "Max 80 characters.", false);
  printToLCDByRow(4, "For a 20x4 LCD.", false);
}

/* MAIN LOOP: runs repeatedly at a very high frequency (1000s of times a second) */
void loop() {
  readSensorValue();
  printToLCD(sensor_value);
}