#include <AccelStepper.h>

#define dirPinLeft 7          // direction left
#define stepPinLeft 8         // step left
#define dirPinRight 3         // direction right
#define stepPinRight 4        // step right
#define motorInterfaceType 1  // bipolar motor

AccelStepper stepperLeft = AccelStepper(motorInterfaceType, stepPinLeft, dirPinLeft);
AccelStepper stepperRight = AccelStepper(motorInterfaceType, stepPinRight, dirPinRight);

const int enPin1 = 9;   // enable pin 1
const int enPin2 = 10;  // enable pin 2

int processEnablerStateVariableCount = 6;  // global state variable for remembering how many times to go

void setup() {
  Serial.begin(9600);

  pinMode(enPin1, INPUT);
  pinMode(enPin2, INPUT);
  digitalWrite(enPin1, HIGH);     /// disable motor control
  digitalWrite(enPin2, HIGH);     /// disable motor control

  stepperLeft.setMaxSpeed(900);
  stepperLeft.setAcceleration(100);
  stepperLeft.moveTo(15);
  stepperRight.setMaxSpeed(900);
  stepperRight.setAcceleration(100);
  stepperRight.moveTo(15);
}

void loop() {
moveSteppers();
}

void moveSteppers() {
  if (processEnablerStateVariableCount > 0) {
    digitalWrite(enPin1, LOW);  /// enable motor control
    digitalWrite(enPin2, LOW);  /// enable motor control

    if (stepperRight.distanceToGo() == 0) {
      stepperRight.moveTo(-stepperRight.currentPosition());
    }
    stepperRight.run();

    if (stepperLeft.distanceToGo() == 0 && processEnablerStateVariableCount > 0) {
      stepperLeft.moveTo(-stepperLeft.currentPosition());
      --processEnablerStateVariableCount;  /// reduce the count by one
    }
    stepperLeft.run();
  }

  digitalWrite(enPin1, HIGH);  /// disable motor control
  digitalWrite(enPin2, HIGH);  /// disable motor control
}