#include "AccelStepper.h"

AccelStepper stepperA (1, 9, 8);
AccelStepper stepperB (1, 5, 4);
AccelStepper stepperC (1, 7, 6);

struct Motor {
    AccelStepper *stepper;
    byte          PinLmtSw;
}
mot [] = {
    { & stepperA, A1, },
    { & stepperB, A2, },
    { & stepperC, A3, },
};

const int Nmot = sizeof(mot)/sizeof(Motor); 

// -------------------------------------
struct Cmd {
    int           motor;
    unsigned long msec;
    int           targPos;
}
cmd [] = {
    { 0, 1000, -1500 },
    { 1, 2000,  1500 },
    { 2, 3000, -1500 },

    { 0, 4000,  -250 },
    { 1, 5000,   250 },
    { 2, 6000,  -250 },
};
const int Ncmd = sizeof(cmd)/sizeof(Cmd); 
int  cmdIdx = 0;

char s [90];

// -----------------------------------------------------------------------------
unsigned long  msec0;

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

    // check if time to update new position
    if (msec - msec0 >= cmd [cmdIdx].msec)  {
        int motorIdx = cmd [cmdIdx].motor;
        int pos      = cmd [cmdIdx].targPos;
        mot [motorIdx].stepper->moveTo (pos);

        if (Ncmd <= ++cmdIdx)  {
            cmdIdx = 0;
            msec0  = msec;
        }

        sprintf (s, " %8lu msec, motor %d, position %6d", msec, motorIdx, pos);
        Serial.println (s);
    }

    // check position and allow motor to run
    for (int n = 0; n < Nmot; n++)  {
        // at limit switch
        if (LOW == digitalRead (mot [n].PinLmtSw))
            mot [n].stepper->stop ();

        // at position zero but limit switch not active
        else if (0 == mot [n].stepper->currentPosition ())  {
            mot [n].stepper->move (-1);
            mot [n].stepper->run  ();
        }

        // allow motor to run
        else
            mot [n].stepper->run ();
    }
}

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

    for (int n = 0; n < Nmot; n++)  {
        mot [n].stepper->setMaxSpeed     (100);
        mot [n].stepper->setAcceleration (200);

        pinMode (mot [n].PinLmtSw, INPUT_PULLUP);

        // "home"
        while (HIGH == digitalRead (mot [n].PinLmtSw)) {
            mot [n].stepper->move (-1);     // toward limtit switch
            mot [n].stepper->run  ();
        }
    }
}