// for https://forum.arduino.cc/t/using-millis-with-a-l293d-motor-shield/981029/7

#include "AFMotor.h" // https://github.com/adafruit/Adafruit-Motor-Shield-library
//
AF_DCMotor motor4 (4);
int motor4State = LOW;
unsigned long previousMillis = 0;
const long interval = 1000;
void setup() {
  AF_DCMotor motor4 (4);
  motor4.setSpeed (254);
  motor4.run(RELEASE);
  motor4.run(FORWARD);
  //turn on motors
}

void loop() {
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;
    if (motor4State)  {
      motor4.run(RELEASE);
      motor4State = HIGH;
    } else {
      motor4.run(FORWARD);
      motor4State = LOW;
    }
  }
}