/* LucidTronix bike Speedometer
 * For instructions, details and schematic, See:
 * http://www.lucidtronix.com/tutorials/13
 * Hall effect sensor on pin 16, 
 * doesn't use hardware interrupt.
 */
#include <LiquidCrystal.h>

LiquidCrystal lcd(4, 5, 0, 1, 2, 3);
String message = "Luf";

int mode = 1;
int num_modes = 2;
int cur_scroll = 0;
int cur_msg_length = 0;
int cursor_index = 0;
int char_index = 0;
int btn = 3;
int hall_pin = 16;
byte backlight_pwm = 200;
int hall_state = 1;
int revolutions = 0;
float miles_in_inches = 63360;
float mph = 0.0;
float distance = 0.0;
float tire_diameter = 26.2;
float k_ipm_2_mph;
int tire_circumference;
unsigned long last_fall = 0;
unsigned long last_interval = 0;

int backlight_pin = 9;
int cur_x = 8;
int cur_y = 1;
void setup() {
  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);
  // Print a message to the LCD.
  delay(500);
  k_ipm_2_mph = 3600000 / miles_in_inches;
  tire_circumference = tire_diameter*3.14159;
  pinMode(btn, INPUT);
  pinMode(hall_pin, INPUT);
  pinMode(backlight_pin, OUTPUT);
  analogWrite(backlight_pin , backlight_pwm);
  lcd.blink();
  lcd.print("hello, world!");
  delay(1000);
}

void loop() {
  int hall_val = digitalRead(hall_pin);
  if (hall_state != hall_val && hall_val == LOW) {
    revolutions++;
    last_interval = millis()-last_fall;
    last_fall = millis();
  }
  hall_state = hall_val;
  updateSpeedAndDistance();
  
  lcd.setCursor(0, 0);
  lcd.print("Hall:" );
  lcd.print( hall_state);
  lcd.print("Mph:");
  lcd.print(mph);
  lcd.setCursor(0, 1);
  lcd.print("Miles:");
  lcd.print(distance);

  backlight_pwm = analogRead(0)/4;
  analogWrite(backlight_pin , backlight_pwm);

}

void updateSpeedAndDistance(){
  distance = tire_circumference * revolutions;
  distance /= miles_in_inches;
  float ipm = tire_circumference / (float)last_interval;
  mph = ipm * k_ipm_2_mph;
}