unsigned long time, timer, eventTime=0, waitUntil_1 =0, waitUntil_2 = 0; //waitUntil_2 to be seeded with Phase shift in PWMs
unsigned long eventInterval =1000; //Time [in mS] interval between each forward reverse event
int fwdPinState, revPinState, stopPinState;

const int fwdPin = 7;
const int revPin = 3;
const int stopPin = 2;

const int PWM1_Pin =  13;      // the number of the Output pin for PWM1 Signal
boolean PWM1_Pin_state =  false;      // the state of PWM1 Signal
const int PWM2_Pin =  12;      // the number of the Output pin for PWM2 Signal
boolean PWM2_Pin_state =  false;      // the state of PWM2 Signal
const int PWM3_Pin =  11;      // the number of the Output pin for PWM3 Signal
boolean PWM3_Pin_state =  false;      // the state of PWM3 Signal
const int PWM4_Pin =  10;      // the number of the Output pin for PWM4 Signal
boolean PWM4_Pin_state =  false;      // the state of PWM4 Signal

boolean resetOnReversal = true; //Allows resettign all the variable once for reversal

int Half_Pulse_Width = 14; //Half pulse width in milli Seconds
int Pulse_Offset = 7; //Pulse offset in milli Seconds

void setup(){
  Serial.begin(9600); // used to debug program and write data to std out during run time
  pinMode(fwdPin, INPUT);     
  pinMode(revPin, INPUT);     
  pinMode(stopPin, INPUT);     

  pinMode(PWM1_Pin, OUTPUT);     
  pinMode(PWM2_Pin, OUTPUT);   
  pinMode(PWM3_Pin, OUTPUT);   
  pinMode(PWM4_Pin, OUTPUT);  
}
void forwardMotor(unsigned long int forEventTime) {
  timer = 0;
  waitUntil_1 = 0;
  waitUntil_2 = Pulse_Offset; //making sure Pulse2_starts after the offset time in mS
  PWM1_Pin_state =  false;
  PWM2_Pin_state =  false;
  PWM3_Pin_state =  false;
  PWM4_Pin_state =  false;
  Serial.print("timer =");
  Serial.print(timer); 
  
  while (timer <= eventInterval) {
     if (timer >= waitUntil_1 ) {
  Serial.print("\n timer =");
  Serial.print(timer); 
        PWM4_Pin_state = !PWM4_Pin_state;
        PWM2_Pin_state = !PWM4_Pin_state;
        waitUntil_1 += Half_Pulse_Width;
      }
    if (timer >= waitUntil_2 ) {
        PWM3_Pin_state = !PWM3_Pin_state;
        PWM1_Pin_state = !PWM3_Pin_state;
        waitUntil_2 += Half_Pulse_Width;
      } 
    digitalWrite(PWM1_Pin, PWM1_Pin_state);
    digitalWrite(PWM2_Pin, PWM2_Pin_state);
    digitalWrite(PWM3_Pin, PWM3_Pin_state);
    digitalWrite(PWM4_Pin, PWM4_Pin_state);
    timer = millis() - forEventTime; 

  }
  return ;
}
void reverseMotor(unsigned long int revEventTime) {
  timer = 0; //re-setting timer to count for reversal          
  waitUntil_1 = 0;
  waitUntil_2 = Pulse_Offset; //making sure Pulse2_starts after the offset time in mS
  PWM1_Pin_state =  false;
  PWM2_Pin_state =  false;
  PWM3_Pin_state =  false;
  PWM4_Pin_state =  false;
  
  while (timer <= eventInterval) {

    if (timer >= waitUntil_1 ) {
        PWM1_Pin_state = !PWM1_Pin_state;
        PWM3_Pin_state = !PWM1_Pin_state;
        waitUntil_1 += Half_Pulse_Width;
      }
    if (timer >= waitUntil_2 ) {
        PWM2_Pin_state = !PWM2_Pin_state ;
        PWM4_Pin_state = !PWM2_Pin_state;
        waitUntil_2 += Half_Pulse_Width;
      }
    digitalWrite(PWM1_Pin, PWM1_Pin_state);
    digitalWrite(PWM2_Pin, PWM2_Pin_state);
    digitalWrite(PWM3_Pin, PWM3_Pin_state);
    digitalWrite(PWM4_Pin, PWM4_Pin_state);
    timer = millis() - revEventTime; 
  }      
     return;
}

void loop(){

  fwdPinState = digitalRead(fwdPin);
  revPinState = digitalRead(revPin);
  stopPinState = digitalRead(stopPin);
 
  if ( fwdPinState == HIGH ) {
   Serial.print("forward =");
 //  Serial.print (time);
   Serial.print (revPinState);
   forwardMotor(millis());
  }
  if ( revPinState == HIGH) {
   Serial.print("Reverse =");
 //  Serial.print (time);
   Serial.print ("\n FPinState =");
   Serial.print (fwdPinState);
   reverseMotor(millis()); 
  }
 }