Accelstepper.runToPosition() is working fine. Accelstepper.run() does nothing

Question

I have a complex sketch with Arduino Uno, Bluetooth Serial Com using altSoftSerial, serial com using SoftwareSerial and Serial communication with PC.

I want to move one stepper motor and stop it when a signal is received. I use A4988 Pololu driver and NEMA 17 bipolar stepper motor.

This code is working fine. MyStepper.moveTo(position); MyStepper.runToPosition();

If I change the code to MyStepper.moveTo(position); MyStepper.run(); so that the running does not block my code the motor does nothing Absolutely no movement.

The ground of the motor power supply is connected with the ground of Arduino. The motor is working fine with blocking movements.

Answer 1

You didn't include any code for us to see what the actual issue is, but I'm willing to guess that you didn't take into account that the run command requires repeated firing.

If your program comes to a point where there's an instance of runToPosition, the blocking function stops the program until the stepper reaches the position specified.

When your program comes to an instance of run(), it fires off a pulse and carries on reading. So you have to use a loop.

stepperMotor.moveTo(3000);
stepperMotor.runToPosition();
// reaches destination

stepperMotor.moveTo(3000);
stepperMotor.run();
// moves a single step

stepperMotor.moveTo(3000);
while (stepperMotor.distanceToGo > 0) {
stepperMotor.run();
}
// reaches destination

The reason you'd use run over runToPosition is to allow for continuous operations / parameters to be executed. For example, two stepper motors running simultaneously:

stepperMotor1.moveTo(5000);
stepperMotor2.moveTo(3000);
while ((stepperMotor1.distanceToGo > 0) && (stepperMotor2.distanceToGo > 0)) {
stepperMotor1.run();
stepperMotor2.run();
}
// Both motors will run, but will both stop when either of them reaches their destination.

Depending on the speed of your microprocessor, you can create some sophisticated instruction sets for your motor(s).

Answer 2

The problem is at blocking delays. The Run function is interrupted by any other action of program. So you have to call it all the time. A call to run is required in the loop and I wrote a simple mydelay function which solves the problem if you have to use delay for bluetooth communication or other purpose.

int mydelay(int j) { 
  long endmillis;
  endmillis = millis() + j;
  while (millis() < endmillis) {
  MyStepper.run();
  }

I hope I help someone because it took me a while to figure this out as a newbie to Arduino.