Accelstepper: missing syncro in simple test program

Question

I have the following test code, which I'm running on an Arduino Yùn. Only PulCyan and DirCyan are connected to Arduino, all the remaining pins are not connected (except ground).

If I run this program I'd expect to have a 500ms stop when the position of the only motor connected (stepperCyan) reaches 0.

However I see that when it reaches position 0, it stops, than it makes 1 step and it stops again, and then it goes at -200 and so on..

How is this possible? I'm quite confused. (code updated thanks to answers below, but still not working properly as described before)

#include <AccelStepper.h>
 
// Define a stepper and the pins it will use
//Stepper motors

int pulYellow = 30;     //N/A on Yùn
int dirYellow = 31;     //N/A on Yùn
//int enaYellow = 32;   //N/A on Yùn
int pulMagenta = 33;    //N/A on Yùn
int dirMagenta = 34;    //N/A on Yùn
//int enaMagenta = 35;  //N/A on Yùn
int pulCyan = 4;   //36 MEGA
int dirCyan = 8;   //37 MEGA
//int enaCyan = 38;   //N/A on Yùn
AccelStepper stepperMagenta(AccelStepper::DRIVER, pulMagenta, dirMagenta);
AccelStepper stepperYellow(AccelStepper::DRIVER, pulYellow, dirYellow);
AccelStepper stepperCyan(AccelStepper::DRIVER, pulCyan, dirCyan);

unsigned long previousMillis = 0;  // will store last time LED was updated
const long interval =500;
void setup()
{  
  // Change these to suit your stepper if you want
  stepperMagenta.setPinsInverted(true, true, true);
  stepperYellow.setPinsInverted(false, false, false);
  stepperCyan.setPinsInverted(true, true, true);
  stepperMagenta.setMinPulseWidth(20);
  stepperYellow.setMinPulseWidth(20);
  stepperCyan.setMinPulseWidth(20);
  stepperMagenta.setMaxSpeed(400);
  stepperMagenta.setAcceleration(200);
  stepperMagenta.moveTo(200);
  stepperYellow.setMaxSpeed(400);
  stepperYellow.setAcceleration(200);
  stepperYellow.moveTo(200);
  stepperCyan.setMaxSpeed(400);
  stepperCyan.setAcceleration(200);
  stepperCyan.moveTo(200);
}
 
void loop()
{
    if (stepperMagenta.currentPosition() == 200 && stepperMagenta.distanceToGo() == 0)
      stepperMagenta.moveTo(0);
    if (stepperMagenta.currentPosition() == 0  && stepperMagenta.distanceToGo() == 0){
      delay(500);
      stepperMagenta.moveTo(-200); 
    } 
    if (stepperMagenta.currentPosition() == -200  && stepperMagenta.distanceToGo() == 0)
      stepperMagenta.moveTo(200);
//-------
    if (stepperYellow.currentPosition() == 200  && stepperYellow.distanceToGo() == 0)
      stepperYellow.moveTo(0);
    if (stepperYellow.currentPosition() == 0  && stepperYellow.distanceToGo() == 0){
      delay(500);
      stepperYellow.moveTo(-200); 
    } 
    if (stepperYellow.currentPosition() == -200   && stepperYellow.distanceToGo() == 0)
      stepperYellow.moveTo(200);
//-------
    if (stepperCyan.currentPosition() == 200 && stepperCyan.distanceToGo() == 0)
      stepperCyan.moveTo(0);
    if (stepperCyan.currentPosition() == 0 && stepperCyan.distanceToGo() == 0){
      delay(500);
      stepperCyan.moveTo(-200); 
    } 
    if (stepperCyan.currentPosition() == -200 && stepperCyan.distanceToGo() == 0)
      stepperCyan.moveTo(200);
//-------      
    stepperMagenta.run();
    stepperYellow.run();
    stepperCyan.run();  
}

The delay(500) pauses execution of the loop(). During this time, the stepper state does not update because stepperCyan.run() isn't being called. — liaifat85
– liaifat85, Commented Jan 11 at 15:20

chrisl · Accepted Answer · 2025-01-06 10:58:11Z

1

That's not, how AccelStepper should be used. The run() method doesn't always execute a step. And it doesn't wait for a step to happen. Instead it checks, if it is time to execute a step. If yes, it does so, if no, it will exit quickly. Thus you need to call run() at least with the frequency of your steps (defined by the speed). With the delay() function you are preventing the AccelStepper library from doing steps, so it will stumble.

If you want to stop at position 0, you should let the stepper run to that position (via moveTo(0)), then wait for 500ms and then move to the next position (via moveTo(-200) for example).

Even better: Instead of using delay(500), use the millis() function like the BlinkWithoutDelay example (that comes with the Arduino IDE) to time the next position change, while not blocking the execution of other code.

answered Jan 6 at 10:58

chrisl

16.6k2 gold badges18 silver badges27 bronze badges

I tried to follow your hints, but it's still making a double stop. (I don't know hot to use millis(), sorry). the new code I wrote for each stepper on the question

Luigi
– Luigi

2025-01-06 12:02:00 +00:00
Commented Jan 6 at 12:02
@Luigi In your updated code you have single &s in the if statements. Was that a typo? For a logical AND you need && (so double &)

chrisl
– chrisl

2025-01-06 12:12:17 +00:00
Commented Jan 6 at 12:12
Thanks, it was a typo. Changed but it's still doing 500ms delay, a small step and again 500ms delay

Luigi
– Luigi

2025-01-06 12:26:16 +00:00
Commented Jan 6 at 12:26

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