// Copyright (C)  2014  Paul T Middlehurst.
// Permission is granted to copy, distribute and/or modify this document
// under the terms of the GNU Free Documentation License, Version 1.3
// or any later version published by the Free Software Foundation;
// with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
// A copy of the license is included in the section entitled "GNU Free Documentation License".
//
//
// PTM DRO V0.1 10th January 2013 
//         V0.2 1st February 2013 3 & 4 DP for mm and inch 

#include <LiquidCrystal.h> 
#define encoder0PinA 3 
#define encoder0PinB 2 
#define zeroPin 5 
#define inchPin 4 

LiquidCrystal lcd(12,11,6,10,9,8,7); 
volatile  long encoder0Pos = 0; 
float tmp = 0; 
long Aold = 0; 
long Bnew = 0;

// change the following line to suit your application
float Mpitch = 1;	//pitch of leadscrew in mm

float Ipitch ;
float Slots = 90;		//slots in wheel

void setup() { 
    Slots *=4;		//convert slots to edges
    Ipitch = Mpitch * 0.0393700787;		// pitch of leadscrew in inches
    pinMode(encoder0PinA, INPUT); 
    pinMode(encoder0PinB, INPUT); 
    pinMode(zeroPin, INPUT); 
    digitalWrite(zeroPin, HIGH); 
    digitalWrite(inchPin, HIGH); 

    lcd.begin(16,2); 
    lcd.clear(); 

    lcd.print("  PTM DRO V0.2"); 
    lcd.setCursor(0,1); 

    // encoder A on interrupt 1 (pin 3) 
    attachInterrupt(1, doEncoderA, CHANGE); 
    // encoder B on interrupt 0 (pin 2) 
    attachInterrupt(0, doEncoderB, CHANGE); 
} 

void loop() { 

    if (tmp != encoder0Pos || (digitalRead(zeroPin) == 0)) { 
        if (digitalRead(zeroPin) == 0) { 
            tmp = 0; 
            encoder0Pos = 0; 
        } 
        if (digitalRead(inchPin) == 0) { 
            tmp = encoder0Pos / Slots * Ipitch; 
            lcd.setCursor(0,1); 
            lcd.print(tmp,4); 
            lcd.print(" inch"); 
        } 
        else { 
            tmp = encoder0Pos / Slots * Mpitch; 
            lcd.setCursor(0,1); 
            lcd.print(tmp,3); 
            lcd.print(" mm"); 
        } 
        lcd.print("                "); 
    } 
} 

// Interrupt A 
void doEncoderA() { 
    // if Bnew = Aold, increment, otherwise decrement 
    Bnew^Aold ? encoder0Pos++:encoder0Pos--; 
    Aold=digitalRead(encoder0PinA); 
} 

// Interrupt B 
void doEncoderB() { 
    Bnew=digitalRead(encoder0PinB); 
    // if Bnew = Aold, increment, otherwise decrement 
    Bnew^Aold ? encoder0Pos++:encoder0Pos--; 
}